Stefania Stefani - Academia.edu (original) (raw)

Papers by Stefania Stefani

Research paper thumbnail of Comparative Evaluation of the BD Phoenix and VITEK 2 Automated Instruments for Identification of Isolates of the Burkholderia cepacia Complex

We evaluated two new automated identification systems, the BD Phoenix (Becton Dickinson) and the ... more We evaluated two new automated identification systems, the BD Phoenix (Becton Dickinson) and the VITEK 2 (bioMérieux), for identification of isolates of the Burkholderia cepacia complex (BCC). The test sample included 42 isolates of the highly virulent and epidemic genomovar III, 45 isolates of B. multivorans, and 47 isolates of other members of the BCC. Rates of correct identification by the BD Phoenix and VITEK 2 were similar when all BCC isolates were considered (50 and 53%, respectively) but differed markedly for genomovar III (71 and 38%; P < 0.01) and for B. multivorans (58 and 89%; P < 0.001). For the BD Phoenix as well as the VITEK 2, taking all 134 isolates of the BCC together, rates of correct identification of clinical isolates (56 and 55%, respectively; n ‫؍‬ 85) were higher than those of environmental isolates (21 and 39%, respectively; n ‫؍‬ 28). Clinical isolates of genomovar III (n ‫؍‬ 27) showed correct identification rates of 81% (BD Phoenix) and 48% (VITEK 2) (P < 0.01). Rates of misidentification for BD Phoenix and VITEK 2 were 9 and 17% for genomovar III, 22 and 7% for B. multivorans, and 36 and 13% for the other BCC members (P < 0.01), respectively. More than half of the isolates misidentified by each instrument were identified as Ralstonia pickettii, Ralstonia paucula (CDC IV C-2 group), Alcaligenes faecalis, Achromobacter spp., or, for the VITEK 2, "various nonfermenters." This study reemphasizes that confirmatory identification of BCC, preferably by molecular methods, is highly recommended.

Research paper thumbnail of Comparative Evaluation of the BD Phoenix and VITEK 2 Automated Instruments for Identification of Isolates of the Burkholderia cepacia Complex

We evaluated two new automated identification systems, the BD Phoenix (Becton Dickinson) and the ... more We evaluated two new automated identification systems, the BD Phoenix (Becton Dickinson) and the VITEK 2 (bioMérieux), for identification of isolates of the Burkholderia cepacia complex (BCC). The test sample included 42 isolates of the highly virulent and epidemic genomovar III, 45 isolates of B. multivorans, and 47 isolates of other members of the BCC. Rates of correct identification by the BD Phoenix and VITEK 2 were similar when all BCC isolates were considered (50 and 53%, respectively) but differed markedly for genomovar III (71 and 38%; P < 0.01) and for B. multivorans (58 and 89%; P < 0.001). For the BD Phoenix as well as the VITEK 2, taking all 134 isolates of the BCC together, rates of correct identification of clinical isolates (56 and 55%, respectively; n ‫؍‬ 85) were higher than those of environmental isolates (21 and 39%, respectively; n ‫؍‬ 28). Clinical isolates of genomovar III (n ‫؍‬ 27) showed correct identification rates of 81% (BD Phoenix) and 48% (VITEK 2) (P < 0.01). Rates of misidentification for BD Phoenix and VITEK 2 were 9 and 17% for genomovar III, 22 and 7% for B. multivorans, and 36 and 13% for the other BCC members (P < 0.01), respectively. More than half of the isolates misidentified by each instrument were identified as Ralstonia pickettii, Ralstonia paucula (CDC IV C-2 group), Alcaligenes faecalis, Achromobacter spp., or, for the VITEK 2, "various nonfermenters." This study reemphasizes that confirmatory identification of BCC, preferably by molecular methods, is highly recommended.

Research paper thumbnail of Lack of Consistent Short Sequence Repeat Polymorphisms in Genetically Homologous Colonizing and Invasive Candida albicans Strains

Short sequence repeats (SSRs), potentially representing variable numbers of tandem repeat (VNTR) ... more Short sequence repeats (SSRs), potentially representing variable numbers of tandem repeat (VNTR) loci, were identified for the human-pathogenic yeast species Candida albicans by computerized DNA sequence scanning. The individual SSR regions were investigated in different clinical isolates of C. albicans. Most of the C. albicans SSRs were identified as genuine VNTRs. They appeared to be present in multiple allelic variants and were demonstrated to be diverse in length among nonrelated strains. As such, these loci provide adequate targets for the molecular typing of C. albicans strains. VNTRs encountered in other microbial species sometimes participate in regulation of gene expression and function as molecular switches at the transcriptional or translational level. Interestingly, the VNTRs identified here often encode polyglutamine stretches and are frequently located within genes potentially involved in the regulation of transcription. DNA sequencing of these VNTRs demonstrated that the length variability was restricted to the CAA/CAG repeats encoding the polyglutamine stretches. For these reasons, paired C. albicans isolates of similar genotype, either found as noninvasive colonizers or encountered in an invasive state in the same individual, were studied with respect to potentially invasion-related alterations in the VNTR profiles. However, none of the VNTRs analyzed thus far varied systematically with the transition from colonization to invasion. In contrast to the situation described for some prokaryotic species, this finding suggests that VNTRs of C. albicans may not simply function as contingency loci related to straightforward on/off regulation of invasion-related gene expression.

Research paper thumbnail of Lack of Consistent Short Sequence Repeat Polymorphisms in Genetically Homologous Colonizing and Invasive Candida albicans Strains

Short sequence repeats (SSRs), potentially representing variable numbers of tandem repeat (VNTR) ... more Short sequence repeats (SSRs), potentially representing variable numbers of tandem repeat (VNTR) loci, were identified for the human-pathogenic yeast species Candida albicans by computerized DNA sequence scanning. The individual SSR regions were investigated in different clinical isolates of C. albicans. Most of the C. albicans SSRs were identified as genuine VNTRs. They appeared to be present in multiple allelic variants and were demonstrated to be diverse in length among nonrelated strains. As such, these loci provide adequate targets for the molecular typing of C. albicans strains. VNTRs encountered in other microbial species sometimes participate in regulation of gene expression and function as molecular switches at the transcriptional or translational level. Interestingly, the VNTRs identified here often encode polyglutamine stretches and are frequently located within genes potentially involved in the regulation of transcription. DNA sequencing of these VNTRs demonstrated that the length variability was restricted to the CAA/CAG repeats encoding the polyglutamine stretches. For these reasons, paired C. albicans isolates of similar genotype, either found as noninvasive colonizers or encountered in an invasive state in the same individual, were studied with respect to potentially invasion-related alterations in the VNTR profiles. However, none of the VNTRs analyzed thus far varied systematically with the transition from colonization to invasion. In contrast to the situation described for some prokaryotic species, this finding suggests that VNTRs of C. albicans may not simply function as contingency loci related to straightforward on/off regulation of invasion-related gene expression.

Research paper thumbnail of Polymerase chain reaction-mediated typing of microorganisms: Tracking dissemination of genes and genomes (minireview

Electrophoresis, 1998

The polymerase chain reaction (PCR) is a powerful molecular biology tool which can be used for th... more The polymerase chain reaction (PCR) is a powerful molecular biology tool which can be used for the identification of species and strains of diverse microorganisms. By aimed amplification of characteristic genes (i.e., genes encoding ribosomal RNA molecules) and subsequent genetic analysis of amplified fragments, information on microbiological systematics and phylogeny can be obtained in a fast and efficient manner. Similar types of gene identification can be used to verify or detect genes responsible for phenotypic characteristics, whereas modified forms of the PCR enable whole genome searches for genetic polymorphisms among strains of a given species. In medical sciences, both strategies, gene and genome variability analysis by PCR, have an increasing impact on the study of the spread of especially those microbes that are multiply resistant to clinically used antibiotics. In this communication we will exemplify the usefulness of PCR-mediated typing of microorganisms from a clinical perspective while focusing on gene- versus genome-scanning. Special emphasis will be placed on analysis of the dissemination and characteristics of methicillin-resistant Staphylococcus aureus (MRSA) strains and bacterial factors providing resistance to penicillin and other β-lactam antibiotics. Technical limitations and possibilities for improvement will be discussed.

Research paper thumbnail of Polymerase chain reaction-mediated typing of microorganisms: Tracking dissemination of genes and genomes (minireview

Electrophoresis, 1998

The polymerase chain reaction (PCR) is a powerful molecular biology tool which can be used for th... more The polymerase chain reaction (PCR) is a powerful molecular biology tool which can be used for the identification of species and strains of diverse microorganisms. By aimed amplification of characteristic genes (i.e., genes encoding ribosomal RNA molecules) and subsequent genetic analysis of amplified fragments, information on microbiological systematics and phylogeny can be obtained in a fast and efficient manner. Similar types of gene identification can be used to verify or detect genes responsible for phenotypic characteristics, whereas modified forms of the PCR enable whole genome searches for genetic polymorphisms among strains of a given species. In medical sciences, both strategies, gene and genome variability analysis by PCR, have an increasing impact on the study of the spread of especially those microbes that are multiply resistant to clinically used antibiotics. In this communication we will exemplify the usefulness of PCR-mediated typing of microorganisms from a clinical perspective while focusing on gene- versus genome-scanning. Special emphasis will be placed on analysis of the dissemination and characteristics of methicillin-resistant Staphylococcus aureus (MRSA) strains and bacterial factors providing resistance to penicillin and other β-lactam antibiotics. Technical limitations and possibilities for improvement will be discussed.

Research paper thumbnail of Comparative Evaluation of the BD Phoenix and VITEK 2 Automated Instruments for Identification of Isolates of the Burkholderia cepacia Complex

We evaluated two new automated identification systems, the BD Phoenix (Becton Dickinson) and the ... more We evaluated two new automated identification systems, the BD Phoenix (Becton Dickinson) and the VITEK 2 (bioMérieux), for identification of isolates of the Burkholderia cepacia complex (BCC). The test sample included 42 isolates of the highly virulent and epidemic genomovar III, 45 isolates of B. multivorans, and 47 isolates of other members of the BCC. Rates of correct identification by the BD Phoenix and VITEK 2 were similar when all BCC isolates were considered (50 and 53%, respectively) but differed markedly for genomovar III (71 and 38%; P < 0.01) and for B. multivorans (58 and 89%; P < 0.001). For the BD Phoenix as well as the VITEK 2, taking all 134 isolates of the BCC together, rates of correct identification of clinical isolates (56 and 55%, respectively; n ‫؍‬ 85) were higher than those of environmental isolates (21 and 39%, respectively; n ‫؍‬ 28). Clinical isolates of genomovar III (n ‫؍‬ 27) showed correct identification rates of 81% (BD Phoenix) and 48% (VITEK 2) (P < 0.01). Rates of misidentification for BD Phoenix and VITEK 2 were 9 and 17% for genomovar III, 22 and 7% for B. multivorans, and 36 and 13% for the other BCC members (P < 0.01), respectively. More than half of the isolates misidentified by each instrument were identified as Ralstonia pickettii, Ralstonia paucula (CDC IV C-2 group), Alcaligenes faecalis, Achromobacter spp., or, for the VITEK 2, "various nonfermenters." This study reemphasizes that confirmatory identification of BCC, preferably by molecular methods, is highly recommended.

Research paper thumbnail of Lack of Consistent Short Sequence Repeat Polymorphisms in Genetically Homologous Colonizing and Invasive Candida albicans Strains

Short sequence repeats (SSRs), potentially representing variable numbers of tandem repeat (VNTR) ... more Short sequence repeats (SSRs), potentially representing variable numbers of tandem repeat (VNTR) loci, were identified for the human-pathogenic yeast species Candida albicans by computerized DNA sequence scanning. The individual SSR regions were investigated in different clinical isolates of C. albicans. Most of the C. albicans SSRs were identified as genuine VNTRs. They appeared to be present in multiple allelic variants and were demonstrated to be diverse in length among nonrelated strains. As such, these loci provide adequate targets for the molecular typing of C. albicans strains. VNTRs encountered in other microbial species sometimes participate in regulation of gene expression and function as molecular switches at the transcriptional or translational level. Interestingly, the VNTRs identified here often encode polyglutamine stretches and are frequently located within genes potentially involved in the regulation of transcription. DNA sequencing of these VNTRs demonstrated that the length variability was restricted to the CAA/CAG repeats encoding the polyglutamine stretches. For these reasons, paired C. albicans isolates of similar genotype, either found as noninvasive colonizers or encountered in an invasive state in the same individual, were studied with respect to potentially invasion-related alterations in the VNTR profiles. However, none of the VNTRs analyzed thus far varied systematically with the transition from colonization to invasion. In contrast to the situation described for some prokaryotic species, this finding suggests that VNTRs of C. albicans may not simply function as contingency loci related to straightforward on/off regulation of invasion-related gene expression.

Research paper thumbnail of Polymerase chain reaction-mediated typing of microorganisms: Tracking dissemination of genes and genomes (minireview

Electrophoresis, 1998

The polymerase chain reaction (PCR) is a powerful molecular biology tool which can be used for th... more The polymerase chain reaction (PCR) is a powerful molecular biology tool which can be used for the identification of species and strains of diverse microorganisms. By aimed amplification of characteristic genes (i.e., genes encoding ribosomal RNA molecules) and subsequent genetic analysis of amplified fragments, information on microbiological systematics and phylogeny can be obtained in a fast and efficient manner. Similar types of gene identification can be used to verify or detect genes responsible for phenotypic characteristics, whereas modified forms of the PCR enable whole genome searches for genetic polymorphisms among strains of a given species. In medical sciences, both strategies, gene and genome variability analysis by PCR, have an increasing impact on the study of the spread of especially those microbes that are multiply resistant to clinically used antibiotics. In this communication we will exemplify the usefulness of PCR-mediated typing of microorganisms from a clinical perspective while focusing on gene- versus genome-scanning. Special emphasis will be placed on analysis of the dissemination and characteristics of methicillin-resistant Staphylococcus aureus (MRSA) strains and bacterial factors providing resistance to penicillin and other β-lactam antibiotics. Technical limitations and possibilities for improvement will be discussed.

Research paper thumbnail of Comparative Evaluation of the BD Phoenix and VITEK 2 Automated Instruments for Identification of Isolates of the Burkholderia cepacia Complex

We evaluated two new automated identification systems, the BD Phoenix (Becton Dickinson) and the ... more We evaluated two new automated identification systems, the BD Phoenix (Becton Dickinson) and the VITEK 2 (bioMérieux), for identification of isolates of the Burkholderia cepacia complex (BCC). The test sample included 42 isolates of the highly virulent and epidemic genomovar III, 45 isolates of B. multivorans, and 47 isolates of other members of the BCC. Rates of correct identification by the BD Phoenix and VITEK 2 were similar when all BCC isolates were considered (50 and 53%, respectively) but differed markedly for genomovar III (71 and 38%; P < 0.01) and for B. multivorans (58 and 89%; P < 0.001). For the BD Phoenix as well as the VITEK 2, taking all 134 isolates of the BCC together, rates of correct identification of clinical isolates (56 and 55%, respectively; n ‫؍‬ 85) were higher than those of environmental isolates (21 and 39%, respectively; n ‫؍‬ 28). Clinical isolates of genomovar III (n ‫؍‬ 27) showed correct identification rates of 81% (BD Phoenix) and 48% (VITEK 2) (P < 0.01). Rates of misidentification for BD Phoenix and VITEK 2 were 9 and 17% for genomovar III, 22 and 7% for B. multivorans, and 36 and 13% for the other BCC members (P < 0.01), respectively. More than half of the isolates misidentified by each instrument were identified as Ralstonia pickettii, Ralstonia paucula (CDC IV C-2 group), Alcaligenes faecalis, Achromobacter spp., or, for the VITEK 2, "various nonfermenters." This study reemphasizes that confirmatory identification of BCC, preferably by molecular methods, is highly recommended.

Research paper thumbnail of Lack of Consistent Short Sequence Repeat Polymorphisms in Genetically Homologous Colonizing and Invasive Candida albicans Strains

Short sequence repeats (SSRs), potentially representing variable numbers of tandem repeat (VNTR) ... more Short sequence repeats (SSRs), potentially representing variable numbers of tandem repeat (VNTR) loci, were identified for the human-pathogenic yeast species Candida albicans by computerized DNA sequence scanning. The individual SSR regions were investigated in different clinical isolates of C. albicans. Most of the C. albicans SSRs were identified as genuine VNTRs. They appeared to be present in multiple allelic variants and were demonstrated to be diverse in length among nonrelated strains. As such, these loci provide adequate targets for the molecular typing of C. albicans strains. VNTRs encountered in other microbial species sometimes participate in regulation of gene expression and function as molecular switches at the transcriptional or translational level. Interestingly, the VNTRs identified here often encode polyglutamine stretches and are frequently located within genes potentially involved in the regulation of transcription. DNA sequencing of these VNTRs demonstrated that the length variability was restricted to the CAA/CAG repeats encoding the polyglutamine stretches. For these reasons, paired C. albicans isolates of similar genotype, either found as noninvasive colonizers or encountered in an invasive state in the same individual, were studied with respect to potentially invasion-related alterations in the VNTR profiles. However, none of the VNTRs analyzed thus far varied systematically with the transition from colonization to invasion. In contrast to the situation described for some prokaryotic species, this finding suggests that VNTRs of C. albicans may not simply function as contingency loci related to straightforward on/off regulation of invasion-related gene expression.

Research paper thumbnail of Polymerase chain reaction-mediated typing of microorganisms: Tracking dissemination of genes and genomes (minireview

Electrophoresis, 1998

The polymerase chain reaction (PCR) is a powerful molecular biology tool which can be used for th... more The polymerase chain reaction (PCR) is a powerful molecular biology tool which can be used for the identification of species and strains of diverse microorganisms. By aimed amplification of characteristic genes (i.e., genes encoding ribosomal RNA molecules) and subsequent genetic analysis of amplified fragments, information on microbiological systematics and phylogeny can be obtained in a fast and efficient manner. Similar types of gene identification can be used to verify or detect genes responsible for phenotypic characteristics, whereas modified forms of the PCR enable whole genome searches for genetic polymorphisms among strains of a given species. In medical sciences, both strategies, gene and genome variability analysis by PCR, have an increasing impact on the study of the spread of especially those microbes that are multiply resistant to clinically used antibiotics. In this communication we will exemplify the usefulness of PCR-mediated typing of microorganisms from a clinical perspective while focusing on gene- versus genome-scanning. Special emphasis will be placed on analysis of the dissemination and characteristics of methicillin-resistant Staphylococcus aureus (MRSA) strains and bacterial factors providing resistance to penicillin and other β-lactam antibiotics. Technical limitations and possibilities for improvement will be discussed.

Research paper thumbnail of Macrolide Efflux Genes mef(A) and mef(E) Are Carried by Different Genetic Elements in Streptococcus pneumoniae

Journal of Clinical Microbiology, 2002

Susceptibilities to macrolides were evaluated in 267 Streptococcus pneumoniae isolates, of which ... more Susceptibilities to macrolides were evaluated in 267 Streptococcus pneumoniae isolates, of which 182 were from patients with invasive diseases and 85 were from healthy carriers. Of the 98 resistant isolates, 20 strains showed an M phenotype and carried mef. Strains that carried both mef(A) and mef(E) were found: 17 strains carried mef(A) and 3 carried mef(E). The characteristics of the strains carrying the mef genes and the properties of the mef-containing elements were studied. Strains carrying mef(A) belonged to serotype 14, were susceptible to all the antibiotics tested except erythromycin, and appeared to be clonally related by pulsed-field gel electrophoresis (PFGE). The three mef(E) strains belonged to different serotypes, showed different susceptibility profiles, and did not appear to be related by PFGE. The sequences of a fragment of the mef-containing element, which encompassed mef and the msr(A) homolog, were identical among the three mef(E)-positive strains and among the three mef(A)-positive strains, although there were differences between the sequences for the two variants at 168 positions. In all mef(A)-positive strains, the mef element was inserted in celB, which led to impairment of the competence of the strains. In line with insertion of the mef(E) element at a different site, the competence of the mef(E)-positive strains was maintained. Transfer of erythromycin resistance by conjugation was obtained from two of three mef(A) strains but from none of three mef(E) strains. Due to the important different characteristics of the strains carrying mef(A) or mef(E), we suggest that the distinction between the two genes be maintained.

Research paper thumbnail of Characterization of a Genetic Element Carrying the Macrolide Efflux Gene mef(A) in Streptococcus pneumoniae

Research paper thumbnail of Cloning and sequencing of a 16S/23S ribosomal spacer from Haemophilus parainfluenzae reveals an invariant, mosaic-like organisation of sequence blocks

Fems Microbiology Letters, 1998

A 16S/23S ribosomal spacer from a Haemophilus parainfluenzae rrn locus was cloned and sequenced. ... more A 16S/23S ribosomal spacer from a Haemophilus parainfluenzae rrn locus was cloned and sequenced. Analysis of PCRamplified genomic fragments showed that this region is strongly conserved among unrelated isolates; computer analysis of database homologies showed that the spacer consists of sequence blocks, arranged in a mosaic-like structure, with strong homologies with analogous blocks present in the spacer regions of Haemophilus influenzae, Haemophilus ducreyi and Actinobacillus spp. It also contains a tRNA qlu gene, which is highly homologous to tRNA qlu genes found in spacers of other species. These data strongly support the hypothesis that recombination events are involved in the organisation of the sequence of the spacer, as a result of horizontal gene transfer. z

Research paper thumbnail of Presence of the ica operon in clinical isolates of Staphylococcus epidermidis and its role in biofilm production

Clinical Microbiology and Infection, 2004

Staphylococcus epidermidis is an important cause of catheter-associated infections, which are att... more Staphylococcus epidermidis is an important cause of catheter-associated infections, which are attributed to its ability to form a multilayered biofilm on polymeric surfaces. This ability depends, in part, on the activity of the icaADBC locus and the icaR gene, which are involved in the production of the polysaccharide intercellular adhesin (PIA) that is functionally necessary for cell-to-cell adhesion and biofilm accumulation. The present study determined: (1) the prevalence of the icaADBC operon in S. epidermidis isolates from catheter-related and other nosocomial infections; (2) the correlation between the presence of this operon, biofilm production and resistance to antibiotics; (3) the expression of ica genes and biofilm production; and (4) the genetic relatedness of the isolates. The results showed that icaRADBC was present in 45% of the isolates included in the study, and that such isolates were significantly more resistant to the main antibiotics tested than were ica-negative isolates. The presence of the entire cluster did not always correlate with biofilm production, determined under different culture conditions, but there was evidence to suggest a correlation when at least two genes (icaAD) were co-transcribed. Eight of 18 ica-positive isolates had the entire operon in the same restriction fragment after pulsed-field gel electrophoresis, but the isolates were not clonal. Estimation of genetic relatedness indicated that ica-positive S. epidermidis isolates belonged to different lineages, distributed in only one of two major clusters, with a genetic distance of c. 0.12.

Research paper thumbnail of Clonal Types and Multidrug Resistance Patterns of Methicillin-Resistant Staphylococcus aureus (MRSA) Recovered in Italy during the 1990s

Microbial Drug Resistance, 2004

Research paper thumbnail of In vitro activity of daptomycin against methicillin- and multi-resistant Staphylococcus haemolyticus invasive isolates carrying different mec complexes

Diagnostic Microbiology and Infectious Disease, 2008

Fifty methicillin and multi-resistant Staphylococcus haemolyticus (MRSH) strains, were tested aga... more Fifty methicillin and multi-resistant Staphylococcus haemolyticus (MRSH) strains, were tested against daptomycin and comparators. Daptomycin showed an overall MIC 90 value of 1 mg/L, similar to that of quinopristin/dalfopristin and lower than the values for vancomycin (2 mg/L), linezolid (2 mg/L) and teicoplanin (32 mg/L). Eighteen strains showed heteroresistant subpopulations with teicoplanin, whereas two strains were also heteroresistant to vancomycin and these sub-populations retained susceptibility to daptomycin. Our results show the good in vitro activity of daptomycin in MRSH strains possessing a multi-resistant phenotype. Clinical data on daptomycin efficacy are necessary to confirm our in vitro findings.

Research paper thumbnail of Identification of a Variant "Rome Clone" of Methicillin-Resistant Staphylococcus aureus with Decreased Susceptibility to Vancomycin, Responsible for an Outbreak in an Intensive Care Unit

Microbial Drug Resistance, 2004

We describe the identification of a variant of the "Rome clone" of methicillin-resistant Staphylo... more We describe the identification of a variant of the "Rome clone" of methicillin-resistant Staphylococcus aureus (MRSA), responsible for an outbreak involving 5 patients in a Cardiac Surgery Intensive Care Unit (CS-ICU) of a tertiary-care University Hospital in Rome. All strains isolated from patients and from nasal swabs obtained from four members of the CS-ICU personnel, belonged to the same identified clone. The characteristics of this clone were: (1) resistance to ampicillin, oxacillin, gentamicin, ciprofloxacin, erythromycin, clindamycin, rifampin, spectinomycin, and tetracycline; (2) vancomycin and teicoplanin MICs respectively of 2 and 4 mg/L; (3) heteroresistant subpopulations in the presence of 4 and 6 mg/L of vancomycin (10 23 and 10 25 , respectively); (4) clonal type I::J::C determined following an established protocol (mecA::Tn554::PFGE); (5) sequence type ST247 , obtained by multilocus sequence typing (MLST); and (6) the staphylococcal cassette chromosome mec (SCC) IA, obtained by multiplex PCR method. This new strain had different characteristics from the epidemic clone circulating in the same hospital from 1997 and designed "Rome clone," which was susceptible to erythromycin, clindamycin, and spectinomycin and belonged to the II::NH::C genetic background. A high genetic similarity between this Rome clone and the previously classified Archaic and Iberian clones was found, because they shared the same allelic profile (ST247), probably originating from the same S. aureus ancestor of the Iberian MRSA strains. Therefore, the strains responsible for the outbreak, with vancomycin MICs 2-4 mg/L, are variant clones, showing the genotype of the "Rome clone," the ST247 in association with SCCmec type IA (ST247-MRSA-IA), and are characterized by a uniform susceptibility to fosfomycin.

Research paper thumbnail of Characterization of a Variant of the SCC mec Element in a Bloodstream Isolate of Staphylococcus intermedius

Microbial Drug Resistance, 2007

S. intermedius is a coagulase-positive zoonotic microrganism, recently classified as a separate s... more S. intermedius is a coagulase-positive zoonotic microrganism, recently classified as a separate species. In routine clinical laboratory practice, the coagulase production is used as criterion of pathogenicity related to S. aureus, but S. intermedius is frequently misidentified-being mistaken for S. aureus-and consequently its real incidence underestimated. S. intermedius have been found only occasionally in human beings, and methicillin-resistance is very rare for this organism. Even if the genetic element responsible for methicillinresistance-the mecA gene carried by diverse staphylococcal chromosomal cassettes-has been described in various staphylococcal species, the current literature doesn't report any case of S. intermedius isolate carrying SCCmec-like elements. Our study could be useful to explain the mechanism and routes of transfer of the chromosomal cassette carrying the mec complex, among staphylococci.

Research paper thumbnail of Comparative Evaluation of the BD Phoenix and VITEK 2 Automated Instruments for Identification of Isolates of the Burkholderia cepacia Complex

We evaluated two new automated identification systems, the BD Phoenix (Becton Dickinson) and the ... more We evaluated two new automated identification systems, the BD Phoenix (Becton Dickinson) and the VITEK 2 (bioMérieux), for identification of isolates of the Burkholderia cepacia complex (BCC). The test sample included 42 isolates of the highly virulent and epidemic genomovar III, 45 isolates of B. multivorans, and 47 isolates of other members of the BCC. Rates of correct identification by the BD Phoenix and VITEK 2 were similar when all BCC isolates were considered (50 and 53%, respectively) but differed markedly for genomovar III (71 and 38%; P < 0.01) and for B. multivorans (58 and 89%; P < 0.001). For the BD Phoenix as well as the VITEK 2, taking all 134 isolates of the BCC together, rates of correct identification of clinical isolates (56 and 55%, respectively; n ‫؍‬ 85) were higher than those of environmental isolates (21 and 39%, respectively; n ‫؍‬ 28). Clinical isolates of genomovar III (n ‫؍‬ 27) showed correct identification rates of 81% (BD Phoenix) and 48% (VITEK 2) (P < 0.01). Rates of misidentification for BD Phoenix and VITEK 2 were 9 and 17% for genomovar III, 22 and 7% for B. multivorans, and 36 and 13% for the other BCC members (P < 0.01), respectively. More than half of the isolates misidentified by each instrument were identified as Ralstonia pickettii, Ralstonia paucula (CDC IV C-2 group), Alcaligenes faecalis, Achromobacter spp., or, for the VITEK 2, "various nonfermenters." This study reemphasizes that confirmatory identification of BCC, preferably by molecular methods, is highly recommended.

Research paper thumbnail of Comparative Evaluation of the BD Phoenix and VITEK 2 Automated Instruments for Identification of Isolates of the Burkholderia cepacia Complex

We evaluated two new automated identification systems, the BD Phoenix (Becton Dickinson) and the ... more We evaluated two new automated identification systems, the BD Phoenix (Becton Dickinson) and the VITEK 2 (bioMérieux), for identification of isolates of the Burkholderia cepacia complex (BCC). The test sample included 42 isolates of the highly virulent and epidemic genomovar III, 45 isolates of B. multivorans, and 47 isolates of other members of the BCC. Rates of correct identification by the BD Phoenix and VITEK 2 were similar when all BCC isolates were considered (50 and 53%, respectively) but differed markedly for genomovar III (71 and 38%; P < 0.01) and for B. multivorans (58 and 89%; P < 0.001). For the BD Phoenix as well as the VITEK 2, taking all 134 isolates of the BCC together, rates of correct identification of clinical isolates (56 and 55%, respectively; n ‫؍‬ 85) were higher than those of environmental isolates (21 and 39%, respectively; n ‫؍‬ 28). Clinical isolates of genomovar III (n ‫؍‬ 27) showed correct identification rates of 81% (BD Phoenix) and 48% (VITEK 2) (P < 0.01). Rates of misidentification for BD Phoenix and VITEK 2 were 9 and 17% for genomovar III, 22 and 7% for B. multivorans, and 36 and 13% for the other BCC members (P < 0.01), respectively. More than half of the isolates misidentified by each instrument were identified as Ralstonia pickettii, Ralstonia paucula (CDC IV C-2 group), Alcaligenes faecalis, Achromobacter spp., or, for the VITEK 2, "various nonfermenters." This study reemphasizes that confirmatory identification of BCC, preferably by molecular methods, is highly recommended.

Research paper thumbnail of Lack of Consistent Short Sequence Repeat Polymorphisms in Genetically Homologous Colonizing and Invasive Candida albicans Strains

Short sequence repeats (SSRs), potentially representing variable numbers of tandem repeat (VNTR) ... more Short sequence repeats (SSRs), potentially representing variable numbers of tandem repeat (VNTR) loci, were identified for the human-pathogenic yeast species Candida albicans by computerized DNA sequence scanning. The individual SSR regions were investigated in different clinical isolates of C. albicans. Most of the C. albicans SSRs were identified as genuine VNTRs. They appeared to be present in multiple allelic variants and were demonstrated to be diverse in length among nonrelated strains. As such, these loci provide adequate targets for the molecular typing of C. albicans strains. VNTRs encountered in other microbial species sometimes participate in regulation of gene expression and function as molecular switches at the transcriptional or translational level. Interestingly, the VNTRs identified here often encode polyglutamine stretches and are frequently located within genes potentially involved in the regulation of transcription. DNA sequencing of these VNTRs demonstrated that the length variability was restricted to the CAA/CAG repeats encoding the polyglutamine stretches. For these reasons, paired C. albicans isolates of similar genotype, either found as noninvasive colonizers or encountered in an invasive state in the same individual, were studied with respect to potentially invasion-related alterations in the VNTR profiles. However, none of the VNTRs analyzed thus far varied systematically with the transition from colonization to invasion. In contrast to the situation described for some prokaryotic species, this finding suggests that VNTRs of C. albicans may not simply function as contingency loci related to straightforward on/off regulation of invasion-related gene expression.

Research paper thumbnail of Lack of Consistent Short Sequence Repeat Polymorphisms in Genetically Homologous Colonizing and Invasive Candida albicans Strains

Short sequence repeats (SSRs), potentially representing variable numbers of tandem repeat (VNTR) ... more Short sequence repeats (SSRs), potentially representing variable numbers of tandem repeat (VNTR) loci, were identified for the human-pathogenic yeast species Candida albicans by computerized DNA sequence scanning. The individual SSR regions were investigated in different clinical isolates of C. albicans. Most of the C. albicans SSRs were identified as genuine VNTRs. They appeared to be present in multiple allelic variants and were demonstrated to be diverse in length among nonrelated strains. As such, these loci provide adequate targets for the molecular typing of C. albicans strains. VNTRs encountered in other microbial species sometimes participate in regulation of gene expression and function as molecular switches at the transcriptional or translational level. Interestingly, the VNTRs identified here often encode polyglutamine stretches and are frequently located within genes potentially involved in the regulation of transcription. DNA sequencing of these VNTRs demonstrated that the length variability was restricted to the CAA/CAG repeats encoding the polyglutamine stretches. For these reasons, paired C. albicans isolates of similar genotype, either found as noninvasive colonizers or encountered in an invasive state in the same individual, were studied with respect to potentially invasion-related alterations in the VNTR profiles. However, none of the VNTRs analyzed thus far varied systematically with the transition from colonization to invasion. In contrast to the situation described for some prokaryotic species, this finding suggests that VNTRs of C. albicans may not simply function as contingency loci related to straightforward on/off regulation of invasion-related gene expression.

Research paper thumbnail of Polymerase chain reaction-mediated typing of microorganisms: Tracking dissemination of genes and genomes (minireview

Electrophoresis, 1998

The polymerase chain reaction (PCR) is a powerful molecular biology tool which can be used for th... more The polymerase chain reaction (PCR) is a powerful molecular biology tool which can be used for the identification of species and strains of diverse microorganisms. By aimed amplification of characteristic genes (i.e., genes encoding ribosomal RNA molecules) and subsequent genetic analysis of amplified fragments, information on microbiological systematics and phylogeny can be obtained in a fast and efficient manner. Similar types of gene identification can be used to verify or detect genes responsible for phenotypic characteristics, whereas modified forms of the PCR enable whole genome searches for genetic polymorphisms among strains of a given species. In medical sciences, both strategies, gene and genome variability analysis by PCR, have an increasing impact on the study of the spread of especially those microbes that are multiply resistant to clinically used antibiotics. In this communication we will exemplify the usefulness of PCR-mediated typing of microorganisms from a clinical perspective while focusing on gene- versus genome-scanning. Special emphasis will be placed on analysis of the dissemination and characteristics of methicillin-resistant Staphylococcus aureus (MRSA) strains and bacterial factors providing resistance to penicillin and other β-lactam antibiotics. Technical limitations and possibilities for improvement will be discussed.

Research paper thumbnail of Polymerase chain reaction-mediated typing of microorganisms: Tracking dissemination of genes and genomes (minireview

Electrophoresis, 1998

The polymerase chain reaction (PCR) is a powerful molecular biology tool which can be used for th... more The polymerase chain reaction (PCR) is a powerful molecular biology tool which can be used for the identification of species and strains of diverse microorganisms. By aimed amplification of characteristic genes (i.e., genes encoding ribosomal RNA molecules) and subsequent genetic analysis of amplified fragments, information on microbiological systematics and phylogeny can be obtained in a fast and efficient manner. Similar types of gene identification can be used to verify or detect genes responsible for phenotypic characteristics, whereas modified forms of the PCR enable whole genome searches for genetic polymorphisms among strains of a given species. In medical sciences, both strategies, gene and genome variability analysis by PCR, have an increasing impact on the study of the spread of especially those microbes that are multiply resistant to clinically used antibiotics. In this communication we will exemplify the usefulness of PCR-mediated typing of microorganisms from a clinical perspective while focusing on gene- versus genome-scanning. Special emphasis will be placed on analysis of the dissemination and characteristics of methicillin-resistant Staphylococcus aureus (MRSA) strains and bacterial factors providing resistance to penicillin and other β-lactam antibiotics. Technical limitations and possibilities for improvement will be discussed.

Research paper thumbnail of Comparative Evaluation of the BD Phoenix and VITEK 2 Automated Instruments for Identification of Isolates of the Burkholderia cepacia Complex

We evaluated two new automated identification systems, the BD Phoenix (Becton Dickinson) and the ... more We evaluated two new automated identification systems, the BD Phoenix (Becton Dickinson) and the VITEK 2 (bioMérieux), for identification of isolates of the Burkholderia cepacia complex (BCC). The test sample included 42 isolates of the highly virulent and epidemic genomovar III, 45 isolates of B. multivorans, and 47 isolates of other members of the BCC. Rates of correct identification by the BD Phoenix and VITEK 2 were similar when all BCC isolates were considered (50 and 53%, respectively) but differed markedly for genomovar III (71 and 38%; P < 0.01) and for B. multivorans (58 and 89%; P < 0.001). For the BD Phoenix as well as the VITEK 2, taking all 134 isolates of the BCC together, rates of correct identification of clinical isolates (56 and 55%, respectively; n ‫؍‬ 85) were higher than those of environmental isolates (21 and 39%, respectively; n ‫؍‬ 28). Clinical isolates of genomovar III (n ‫؍‬ 27) showed correct identification rates of 81% (BD Phoenix) and 48% (VITEK 2) (P < 0.01). Rates of misidentification for BD Phoenix and VITEK 2 were 9 and 17% for genomovar III, 22 and 7% for B. multivorans, and 36 and 13% for the other BCC members (P < 0.01), respectively. More than half of the isolates misidentified by each instrument were identified as Ralstonia pickettii, Ralstonia paucula (CDC IV C-2 group), Alcaligenes faecalis, Achromobacter spp., or, for the VITEK 2, "various nonfermenters." This study reemphasizes that confirmatory identification of BCC, preferably by molecular methods, is highly recommended.

Research paper thumbnail of Lack of Consistent Short Sequence Repeat Polymorphisms in Genetically Homologous Colonizing and Invasive Candida albicans Strains

Short sequence repeats (SSRs), potentially representing variable numbers of tandem repeat (VNTR) ... more Short sequence repeats (SSRs), potentially representing variable numbers of tandem repeat (VNTR) loci, were identified for the human-pathogenic yeast species Candida albicans by computerized DNA sequence scanning. The individual SSR regions were investigated in different clinical isolates of C. albicans. Most of the C. albicans SSRs were identified as genuine VNTRs. They appeared to be present in multiple allelic variants and were demonstrated to be diverse in length among nonrelated strains. As such, these loci provide adequate targets for the molecular typing of C. albicans strains. VNTRs encountered in other microbial species sometimes participate in regulation of gene expression and function as molecular switches at the transcriptional or translational level. Interestingly, the VNTRs identified here often encode polyglutamine stretches and are frequently located within genes potentially involved in the regulation of transcription. DNA sequencing of these VNTRs demonstrated that the length variability was restricted to the CAA/CAG repeats encoding the polyglutamine stretches. For these reasons, paired C. albicans isolates of similar genotype, either found as noninvasive colonizers or encountered in an invasive state in the same individual, were studied with respect to potentially invasion-related alterations in the VNTR profiles. However, none of the VNTRs analyzed thus far varied systematically with the transition from colonization to invasion. In contrast to the situation described for some prokaryotic species, this finding suggests that VNTRs of C. albicans may not simply function as contingency loci related to straightforward on/off regulation of invasion-related gene expression.

Research paper thumbnail of Polymerase chain reaction-mediated typing of microorganisms: Tracking dissemination of genes and genomes (minireview

Electrophoresis, 1998

The polymerase chain reaction (PCR) is a powerful molecular biology tool which can be used for th... more The polymerase chain reaction (PCR) is a powerful molecular biology tool which can be used for the identification of species and strains of diverse microorganisms. By aimed amplification of characteristic genes (i.e., genes encoding ribosomal RNA molecules) and subsequent genetic analysis of amplified fragments, information on microbiological systematics and phylogeny can be obtained in a fast and efficient manner. Similar types of gene identification can be used to verify or detect genes responsible for phenotypic characteristics, whereas modified forms of the PCR enable whole genome searches for genetic polymorphisms among strains of a given species. In medical sciences, both strategies, gene and genome variability analysis by PCR, have an increasing impact on the study of the spread of especially those microbes that are multiply resistant to clinically used antibiotics. In this communication we will exemplify the usefulness of PCR-mediated typing of microorganisms from a clinical perspective while focusing on gene- versus genome-scanning. Special emphasis will be placed on analysis of the dissemination and characteristics of methicillin-resistant Staphylococcus aureus (MRSA) strains and bacterial factors providing resistance to penicillin and other β-lactam antibiotics. Technical limitations and possibilities for improvement will be discussed.

Research paper thumbnail of Comparative Evaluation of the BD Phoenix and VITEK 2 Automated Instruments for Identification of Isolates of the Burkholderia cepacia Complex

We evaluated two new automated identification systems, the BD Phoenix (Becton Dickinson) and the ... more We evaluated two new automated identification systems, the BD Phoenix (Becton Dickinson) and the VITEK 2 (bioMérieux), for identification of isolates of the Burkholderia cepacia complex (BCC). The test sample included 42 isolates of the highly virulent and epidemic genomovar III, 45 isolates of B. multivorans, and 47 isolates of other members of the BCC. Rates of correct identification by the BD Phoenix and VITEK 2 were similar when all BCC isolates were considered (50 and 53%, respectively) but differed markedly for genomovar III (71 and 38%; P < 0.01) and for B. multivorans (58 and 89%; P < 0.001). For the BD Phoenix as well as the VITEK 2, taking all 134 isolates of the BCC together, rates of correct identification of clinical isolates (56 and 55%, respectively; n ‫؍‬ 85) were higher than those of environmental isolates (21 and 39%, respectively; n ‫؍‬ 28). Clinical isolates of genomovar III (n ‫؍‬ 27) showed correct identification rates of 81% (BD Phoenix) and 48% (VITEK 2) (P < 0.01). Rates of misidentification for BD Phoenix and VITEK 2 were 9 and 17% for genomovar III, 22 and 7% for B. multivorans, and 36 and 13% for the other BCC members (P < 0.01), respectively. More than half of the isolates misidentified by each instrument were identified as Ralstonia pickettii, Ralstonia paucula (CDC IV C-2 group), Alcaligenes faecalis, Achromobacter spp., or, for the VITEK 2, "various nonfermenters." This study reemphasizes that confirmatory identification of BCC, preferably by molecular methods, is highly recommended.

Research paper thumbnail of Lack of Consistent Short Sequence Repeat Polymorphisms in Genetically Homologous Colonizing and Invasive Candida albicans Strains

Short sequence repeats (SSRs), potentially representing variable numbers of tandem repeat (VNTR) ... more Short sequence repeats (SSRs), potentially representing variable numbers of tandem repeat (VNTR) loci, were identified for the human-pathogenic yeast species Candida albicans by computerized DNA sequence scanning. The individual SSR regions were investigated in different clinical isolates of C. albicans. Most of the C. albicans SSRs were identified as genuine VNTRs. They appeared to be present in multiple allelic variants and were demonstrated to be diverse in length among nonrelated strains. As such, these loci provide adequate targets for the molecular typing of C. albicans strains. VNTRs encountered in other microbial species sometimes participate in regulation of gene expression and function as molecular switches at the transcriptional or translational level. Interestingly, the VNTRs identified here often encode polyglutamine stretches and are frequently located within genes potentially involved in the regulation of transcription. DNA sequencing of these VNTRs demonstrated that the length variability was restricted to the CAA/CAG repeats encoding the polyglutamine stretches. For these reasons, paired C. albicans isolates of similar genotype, either found as noninvasive colonizers or encountered in an invasive state in the same individual, were studied with respect to potentially invasion-related alterations in the VNTR profiles. However, none of the VNTRs analyzed thus far varied systematically with the transition from colonization to invasion. In contrast to the situation described for some prokaryotic species, this finding suggests that VNTRs of C. albicans may not simply function as contingency loci related to straightforward on/off regulation of invasion-related gene expression.

Research paper thumbnail of Polymerase chain reaction-mediated typing of microorganisms: Tracking dissemination of genes and genomes (minireview

Electrophoresis, 1998

The polymerase chain reaction (PCR) is a powerful molecular biology tool which can be used for th... more The polymerase chain reaction (PCR) is a powerful molecular biology tool which can be used for the identification of species and strains of diverse microorganisms. By aimed amplification of characteristic genes (i.e., genes encoding ribosomal RNA molecules) and subsequent genetic analysis of amplified fragments, information on microbiological systematics and phylogeny can be obtained in a fast and efficient manner. Similar types of gene identification can be used to verify or detect genes responsible for phenotypic characteristics, whereas modified forms of the PCR enable whole genome searches for genetic polymorphisms among strains of a given species. In medical sciences, both strategies, gene and genome variability analysis by PCR, have an increasing impact on the study of the spread of especially those microbes that are multiply resistant to clinically used antibiotics. In this communication we will exemplify the usefulness of PCR-mediated typing of microorganisms from a clinical perspective while focusing on gene- versus genome-scanning. Special emphasis will be placed on analysis of the dissemination and characteristics of methicillin-resistant Staphylococcus aureus (MRSA) strains and bacterial factors providing resistance to penicillin and other β-lactam antibiotics. Technical limitations and possibilities for improvement will be discussed.

Research paper thumbnail of Macrolide Efflux Genes mef(A) and mef(E) Are Carried by Different Genetic Elements in Streptococcus pneumoniae

Journal of Clinical Microbiology, 2002

Susceptibilities to macrolides were evaluated in 267 Streptococcus pneumoniae isolates, of which ... more Susceptibilities to macrolides were evaluated in 267 Streptococcus pneumoniae isolates, of which 182 were from patients with invasive diseases and 85 were from healthy carriers. Of the 98 resistant isolates, 20 strains showed an M phenotype and carried mef. Strains that carried both mef(A) and mef(E) were found: 17 strains carried mef(A) and 3 carried mef(E). The characteristics of the strains carrying the mef genes and the properties of the mef-containing elements were studied. Strains carrying mef(A) belonged to serotype 14, were susceptible to all the antibiotics tested except erythromycin, and appeared to be clonally related by pulsed-field gel electrophoresis (PFGE). The three mef(E) strains belonged to different serotypes, showed different susceptibility profiles, and did not appear to be related by PFGE. The sequences of a fragment of the mef-containing element, which encompassed mef and the msr(A) homolog, were identical among the three mef(E)-positive strains and among the three mef(A)-positive strains, although there were differences between the sequences for the two variants at 168 positions. In all mef(A)-positive strains, the mef element was inserted in celB, which led to impairment of the competence of the strains. In line with insertion of the mef(E) element at a different site, the competence of the mef(E)-positive strains was maintained. Transfer of erythromycin resistance by conjugation was obtained from two of three mef(A) strains but from none of three mef(E) strains. Due to the important different characteristics of the strains carrying mef(A) or mef(E), we suggest that the distinction between the two genes be maintained.

Research paper thumbnail of Characterization of a Genetic Element Carrying the Macrolide Efflux Gene mef(A) in Streptococcus pneumoniae

Research paper thumbnail of Cloning and sequencing of a 16S/23S ribosomal spacer from Haemophilus parainfluenzae reveals an invariant, mosaic-like organisation of sequence blocks

Fems Microbiology Letters, 1998

A 16S/23S ribosomal spacer from a Haemophilus parainfluenzae rrn locus was cloned and sequenced. ... more A 16S/23S ribosomal spacer from a Haemophilus parainfluenzae rrn locus was cloned and sequenced. Analysis of PCRamplified genomic fragments showed that this region is strongly conserved among unrelated isolates; computer analysis of database homologies showed that the spacer consists of sequence blocks, arranged in a mosaic-like structure, with strong homologies with analogous blocks present in the spacer regions of Haemophilus influenzae, Haemophilus ducreyi and Actinobacillus spp. It also contains a tRNA qlu gene, which is highly homologous to tRNA qlu genes found in spacers of other species. These data strongly support the hypothesis that recombination events are involved in the organisation of the sequence of the spacer, as a result of horizontal gene transfer. z

Research paper thumbnail of Presence of the ica operon in clinical isolates of Staphylococcus epidermidis and its role in biofilm production

Clinical Microbiology and Infection, 2004

Staphylococcus epidermidis is an important cause of catheter-associated infections, which are att... more Staphylococcus epidermidis is an important cause of catheter-associated infections, which are attributed to its ability to form a multilayered biofilm on polymeric surfaces. This ability depends, in part, on the activity of the icaADBC locus and the icaR gene, which are involved in the production of the polysaccharide intercellular adhesin (PIA) that is functionally necessary for cell-to-cell adhesion and biofilm accumulation. The present study determined: (1) the prevalence of the icaADBC operon in S. epidermidis isolates from catheter-related and other nosocomial infections; (2) the correlation between the presence of this operon, biofilm production and resistance to antibiotics; (3) the expression of ica genes and biofilm production; and (4) the genetic relatedness of the isolates. The results showed that icaRADBC was present in 45% of the isolates included in the study, and that such isolates were significantly more resistant to the main antibiotics tested than were ica-negative isolates. The presence of the entire cluster did not always correlate with biofilm production, determined under different culture conditions, but there was evidence to suggest a correlation when at least two genes (icaAD) were co-transcribed. Eight of 18 ica-positive isolates had the entire operon in the same restriction fragment after pulsed-field gel electrophoresis, but the isolates were not clonal. Estimation of genetic relatedness indicated that ica-positive S. epidermidis isolates belonged to different lineages, distributed in only one of two major clusters, with a genetic distance of c. 0.12.

Research paper thumbnail of Clonal Types and Multidrug Resistance Patterns of Methicillin-Resistant Staphylococcus aureus (MRSA) Recovered in Italy during the 1990s

Microbial Drug Resistance, 2004

Research paper thumbnail of In vitro activity of daptomycin against methicillin- and multi-resistant Staphylococcus haemolyticus invasive isolates carrying different mec complexes

Diagnostic Microbiology and Infectious Disease, 2008

Fifty methicillin and multi-resistant Staphylococcus haemolyticus (MRSH) strains, were tested aga... more Fifty methicillin and multi-resistant Staphylococcus haemolyticus (MRSH) strains, were tested against daptomycin and comparators. Daptomycin showed an overall MIC 90 value of 1 mg/L, similar to that of quinopristin/dalfopristin and lower than the values for vancomycin (2 mg/L), linezolid (2 mg/L) and teicoplanin (32 mg/L). Eighteen strains showed heteroresistant subpopulations with teicoplanin, whereas two strains were also heteroresistant to vancomycin and these sub-populations retained susceptibility to daptomycin. Our results show the good in vitro activity of daptomycin in MRSH strains possessing a multi-resistant phenotype. Clinical data on daptomycin efficacy are necessary to confirm our in vitro findings.

Research paper thumbnail of Identification of a Variant "Rome Clone" of Methicillin-Resistant Staphylococcus aureus with Decreased Susceptibility to Vancomycin, Responsible for an Outbreak in an Intensive Care Unit

Microbial Drug Resistance, 2004

We describe the identification of a variant of the "Rome clone" of methicillin-resistant Staphylo... more We describe the identification of a variant of the "Rome clone" of methicillin-resistant Staphylococcus aureus (MRSA), responsible for an outbreak involving 5 patients in a Cardiac Surgery Intensive Care Unit (CS-ICU) of a tertiary-care University Hospital in Rome. All strains isolated from patients and from nasal swabs obtained from four members of the CS-ICU personnel, belonged to the same identified clone. The characteristics of this clone were: (1) resistance to ampicillin, oxacillin, gentamicin, ciprofloxacin, erythromycin, clindamycin, rifampin, spectinomycin, and tetracycline; (2) vancomycin and teicoplanin MICs respectively of 2 and 4 mg/L; (3) heteroresistant subpopulations in the presence of 4 and 6 mg/L of vancomycin (10 23 and 10 25 , respectively); (4) clonal type I::J::C determined following an established protocol (mecA::Tn554::PFGE); (5) sequence type ST247 , obtained by multilocus sequence typing (MLST); and (6) the staphylococcal cassette chromosome mec (SCC) IA, obtained by multiplex PCR method. This new strain had different characteristics from the epidemic clone circulating in the same hospital from 1997 and designed "Rome clone," which was susceptible to erythromycin, clindamycin, and spectinomycin and belonged to the II::NH::C genetic background. A high genetic similarity between this Rome clone and the previously classified Archaic and Iberian clones was found, because they shared the same allelic profile (ST247), probably originating from the same S. aureus ancestor of the Iberian MRSA strains. Therefore, the strains responsible for the outbreak, with vancomycin MICs 2-4 mg/L, are variant clones, showing the genotype of the "Rome clone," the ST247 in association with SCCmec type IA (ST247-MRSA-IA), and are characterized by a uniform susceptibility to fosfomycin.

Research paper thumbnail of Characterization of a Variant of the SCC mec Element in a Bloodstream Isolate of Staphylococcus intermedius

Microbial Drug Resistance, 2007

S. intermedius is a coagulase-positive zoonotic microrganism, recently classified as a separate s... more S. intermedius is a coagulase-positive zoonotic microrganism, recently classified as a separate species. In routine clinical laboratory practice, the coagulase production is used as criterion of pathogenicity related to S. aureus, but S. intermedius is frequently misidentified-being mistaken for S. aureus-and consequently its real incidence underestimated. S. intermedius have been found only occasionally in human beings, and methicillin-resistance is very rare for this organism. Even if the genetic element responsible for methicillinresistance-the mecA gene carried by diverse staphylococcal chromosomal cassettes-has been described in various staphylococcal species, the current literature doesn't report any case of S. intermedius isolate carrying SCCmec-like elements. Our study could be useful to explain the mechanism and routes of transfer of the chromosomal cassette carrying the mec complex, among staphylococci.