Taschia Bertuccio | Università di Catania (original) (raw)

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Papers by Taschia Bertuccio

PloS one, 2014

Development of in vivo daptomycin resistance (DAP-R) among Staphylococcus aureus clinical isolate... more Development of in vivo daptomycin resistance (DAP-R) among Staphylococcus aureus clinical isolates, in association with clinical treatment failures, has become a major therapeutic problem. This issue is especially relevant to methicillin-resistant S. aureus (MRSA) strains in the context of invasive endovascular infections. In the current study, we used three well-characterized and clinically-derived DAP-susceptible (DAP-S) vs. resistant (DAP-R) MRSA strain-pairs to elucidate potential genotypic mechanisms of the DAP-R phenotype. In comparison to the DAP-S parental strains, DAP-R isolates demonstrated (i) altered expression of two key determinants of net positive surface charge, either during exponential or stationary growth phases (i.e., dysregulation of dltA and mprF), (ii) a significant increase in the D-alanylated wall teichoic acid (WTA) content in DAP-R strains, reflecting DltA gain-in-function; (iii) heightened elaboration of lysinylated-phosphatidylglyderol (L-PG) in DAP-R st...

Journal of Cystic Fibrosis, 2008

International Journal of Antimicrobial Agents, 2007

Methods: Twenty six S. pyogenes clinical isolates from different origins and expressing different... more Methods: Twenty six S. pyogenes clinical isolates from different origins and expressing different M types were included in this study. To investigate the role of the hyaluronic acid capsule, the Emm18 protein and the Enn18 protein, we used a set of mutants derived from the wild type strain 87-282 including the Emm18 protein deficient mutant 282KZ and the capsule deficient mutant TX72. Isogenic mutants TX74 and TX76, derived from TX72, deficient in the Emm18 protein and the Enn18 protein, respectively, were also included in the study. Binding of CD46 was determined by incubation of the bacteria with purified recombinant soluble human CD46. CD46 binding to each strain was determined by Western blot analysis using policlonal anti-CD46 antibodies. Binding of CD46 to purified recombinant Emm18 protein was determined by ELISA. Results: Binding assays showed that CD46 binding to S. pyogenes was highly variable among the 17 different M types tested, being M type 18 strains among those showing the strongest binding. The binding of purified human CD46 to M type 18 strains was independent of the expression of the hyaluronic acid capsule, since the highly mucoid strain 87-282 bound CD46 as efficiently as the derived capsule deficient mutant TX72. Surprisingly, the Emm18 protein deficient mutants 282-KZ and TX74 bound CD46. Moreover, CD46 did not bind to purified recombinant Emm18 constructs, suggesting that the Emm18 protein is not involved in the binding of CD46 to the M type 18 strains. To test another protein candidate for CD46 binding to S. pyogenes M type 18, we generated the strain TX76. TX76 bound CD46 as efficiently as the strains TX72 and TX74. Conclusion: Binding of human CD46 to S. pyogenes is highly heterogeneous and do not depend on the presence of hyaluronic acid capsule. Despite Emm proteins have been assumed to mediate binding of S. pyogenes to CD46, M type18 strains bind CD46 very efficiently through a cell surface protein different from the Emm and Enn proteins.

International Journal of Antimicrobial Agents, 2010

International Journal of Antimicrobial Agents, 2014

The mechanisms leading to reduced susceptibility to daptomycin (DAP) are multifactorial and have ... more The mechanisms leading to reduced susceptibility to daptomycin (DAP) are multifactorial and have not been fully elucidated. We analysed, by sequencing and expression studies, the role of the major molecular targets (cell-envelope charge genes, dltA, mprF, cls2; cell-wall turnover and autolysis genes, sceD, atl) involved in the emergence of DAP resistance in three series of isogenic clinical methicillin-resistant Staphylococcus aureus (MRSA) in which DAP resistance emerged after a heterogeneous glycopeptideintermediate S. aureus (hGISA) step under teicoplanin and DAP therapy. All of the isolates had different genotypes and were ␦-haemolysin negative, reflecting a strain proclivity to acquire DAP/glycopeptide non-susceptibility under antibiotic pressure. DAP exposure led to the emergence of DAP resistance after an hGISA step probably in parallel with the timing of the two antimicrobial administrations and, in two of three cases, in conditions of DAP underdosage. Real-time qPCR data revealed that all DAP-resistant (DAP-R) isolates had dltA overexpression, whereas mprF upregulation was found only in DAP-R strains with the S295L and T345I amino acid substitutions. Strains that were heteroresistant to DAP did not possess DAP-R-like characteristics. DAP-R strains presented high cls2 expression and no known cls2 mutations, and moreover exhibited sceD and atl upregulation. In conclusion, these findings highlight that dltA overexpression is the common pathway of resistance among genotypically different series of isolates and may represent the keystone of DAP resistance in MRSA, leading to electrostatic repulsion and, indirectly, to a reduction of autolysin activity. mprF mutations related to increased transcription may play a role in this complex phenomenon.

FEMS Immunology & Medical Microbiology, 2010

The purpose of our study was to evaluate the anti-staphylococcal biofilm activity of tigecycline,... more The purpose of our study was to evaluate the anti-staphylococcal biofilm activity of tigecycline, compared with a group of recently developed or commonly used antimicrobials such as linezolid, daptomycin, levofloxacin, tobramycin and rifampin, all possessing putative antibiofilm properties, on a sample of multidrug-resistant methicillin-resistant Staphylococcus aureus grown as a planktonic and mature biofilm. We determined conventional minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) for the planktonic forms, MICs of adherent cells and finally, minimum biofilm eradication concentrations (MBECs). No drug was able to inhibit adherent bacteria at the same concentration necessary for eradicating a mature biofilm; the latter concentrations varied from three to seven times higher than the ones inhibiting adhesion. The concentrations eradicating biofilm were reached by rifampin and daptomycin at lower concentrations with respect to the other antibiotics tested; tigecycline was able to inhibit mature biofilms at higher concentrations, while all the other antibiotics were only able to inhibit adhering cells.

FEMS Immunology & Medical Microbiology, 2007

We investigated the correlation between biofilm production and the accessorygene-regulator (agr) ... more We investigated the correlation between biofilm production and the accessorygene-regulator (agr) in 29 strains isolated from catheter-associated infections compared to a control group (30 isolates). All strains were tested for their ability to produce biofilm in a static system, and their agr genotype was determined. ScaIrestriction fragment length polymorphism for agr-typing showed that strong biofilm-producing strains belong to agr-type II. We found two new agr-variants, and sequence analysis of the three PCR products revealed the insertion of IS256 within the agr-locus. Biofilm production was assessed and correlated with agr functionality, with the expression of the ica-operon and of two transcriptional regulators, sarA and rsbU. Our data show that agr-II strains produce large amounts of biofilm, possess a defective agr-system show early transcription of icaA and are defective in haemolysin activity, icaR transcription, and in the expression of the s B activator rsbU. Strains with agrIII are medium biofilm producers, have an inactive agr-system, but express icaAR and rsbU in the late-and postexponential growth phases. In agrI-IV-and -IA-variants, medium or weak biofilm production was found. In these strains, the agr-locus was fully functional, rsbU-icaR and icaA were found in the late-and/or postexponential phases. Biofilm production was not affected by sarA.

European Journal of Clinical Microbiology & Infectious Diseases, 2010

Methicilllin-resistant Staphylococcus aureus (MRSA) infections are increasingly reported in cysti... more Methicilllin-resistant Staphylococcus aureus (MRSA) infections are increasingly reported in cystic fibrosis (CF) populations worldwide. In this paper, we sought to look at the epidemiology, the molecular characterization and the antibiotic resistance of MRSA isolates in our cohort of CF patients. All MRSA were collected prospectively at the University Hospital of Catania (I) in a two-year study between mid 2005 -mid 2007 and underwent molecular, pathotype and susceptibility characterizations. Our study demonstrates persisting infections with both HA-and CA-MRSA including PVL-positive strains in our CF population with an overall prevalence of 7.8%. We demonstrated that in these patients, persistence was sustained by either identical clones that underwent subtle changes in their toxin content or by different clones over time. The isolation of MRSA in our CF population aged 7-24, was associated with an increased severity of the disease even if, due to the small sample of patients included and the paucity of data on the clinical outcome, these results cannot be conclusive. Furthermore, 35.7% of strains were hVISA, questioning the use of glycopeptides in the treatment of MRSA infections in these patients.

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.