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Papers by Agostinho Alves de Lima e Silva

African Journal of Microbiology Research, Apr 8, 2015

Staphylococcus epidermidis is considered as the main infectious agent associated with implanted m... more Staphylococcus epidermidis is considered as the main infectious agent associated with implanted medical devices. This study determined biofilm production and composition, pulsed-field gel electrophoresis (PFGE) profile, antimicrobial susceptibility and presence of virulence-related genes (ica operon, aap, bhp, embp, capB and IS256 transposase) in 49 clinical isolates of S. epidermidis. Twenty-five isolates (51%) were classified as biofilm producers in microtiter plate (MTP) assay. In Congo red assay (CRA) test, 14 (29%) showed positive reaction and three (6%) had indeterminate reaction, all were biofilmproducers in MTP assay. Fourteen isolates with positive reaction in CRA test had the chemical nature of biofilm determined as polysaccharide, had the ica operon (PIA-dependent producers) and the majority was strong biofilm producer. Eight biofilm producer isolates showed negative reaction in CRA test and the chemical nature of their biofilm was proteinaceous (PIA-independent producers). Antimicrobial resistance rates were generally higher in biofilm producers and resistance to beta-lactams ranged from 82-96%, while 61% of the isolates were multidrug resistant (≥ 10 drugs). Resistance to daptomycin, quinupristin/dalfopristin, rifampin and trimethoprim/sulfamethoxazole was observed only in PIAdependent isolates, while the resistance to gentamicin was present in all PIA-independent isolates and in just 53% of PIA-dependent of isolates. The most prevalent virulence-related genes were capB (80%) and embp (67%); the other genes were less frequent: ica operon (41%), aap (31%), IS256 transposase (22%) and bhp (10%). The presence of ica operon and IS256 transposase gene showed significant association with biofilm production and strong biofilm production. Moreover, these isolates presented significant higher resistance to levofloxacin, moxifloxacin, rifampin and trimethoprim/sulfamethoxazole. PFGE analysis showed 23 profiles, having the prevalent type 15 isolates. Of these, seven were PIAindependent biofilm producers and just one was PIA-dependent producer, unlike what was observed in other studies, where isolates of prevalent profiles were PIA-dependent biofilm producers.

Environmental Toxicology & Water Quality, 1993

Escherichia coli isolated from the intestinal tract of marine fish captured along polluted beache... more Escherichia coli isolated from the intestinal tract of marine fish captured along polluted beaches of the city of Rio de Janeiro, Brazil, were investigated in terms of resistance to seven antibiotics and to four heavy metals. Approximately 40% of the strains were resistant to one or more antibiotics, with predominance of mono- and biresistance. Overall resistance to heavy metals was 70.7%, and exclusive resistance to these elements was more elevated than resistance to antibiotics only. Resistance to mercury was closely associated with resistance to antibiotics and with multiple resistance in particular. Most of the strains analyzed transferred resistance determinants to standard receptor strains during conjugation, the phenomenon being particularly outstanding for the transfer of the copper marker. The epidemiological and ecological aspects of the results obtained are discussed. © 1993 John Wiley & Sons, Inc.

Brazilian Journal of Microbiology, 2012

Samples of sewage from a university hospital and a chemistry technical school were analysed for t... more Samples of sewage from a university hospital and a chemistry technical school were analysed for the percentage of bacterial tolerance to chromium (Cr), silver (Ag) and mercury (Hg). Additionally, we investigated the effect of these metals on pigmentation and on some enzymatic activities of the metal tolerant strains isolated, as well as antimicrobial resistance in some metal tolerant Enterobacteriaceae strains. Tolerance to Cr was observed mainly in Gram positive bacteria while in the case of Ag and Hg the tolerant bacteria were predominately Gram negative. Hg was the metal for which the percentage of tolerance was significantly higher, especially in samples from the hospital sewage (4.1%). Mercury also had the most discernible effect on color of the colonies. Considering the effect of metals on the respiratory enzymes, one strain of Ag-tolerant Bacillus sp. and one of Hg-tolerant P. aeruginosa were unable to produce oxidase in the presence of Ag and Hg, respectively, while the expression of gelatinase was largely inhibited in various Gram negative strains (66% by Cr). Drug resistance in Hg-tolerant Enterobacteriaceae strains isolated from the university hospital sewage was greater than 80%, with prevalence of multiple resistance, while the Agtolerant strains from the same source showed about 34% of resistance, with the predominance of monoresistance. Our results showed that, despite the ability of metal tolerant strains to survive and grow in the presence of these elements, the interactions with these metals may result in metabolic or phisiological changes in this group of bacteria.

Strains of Cr-tolerant or Hg-tolerant Gram-negative bacteria were isolated from Chemistry School&... more Strains of Cr-tolerant or Hg-tolerant Gram-negative bacteria were isolated from Chemistry School's sewage water and these were studied in relation to their ability to use phenol as sole carbon source in the presence of K2Cr2O7 and HgCl2. These metals showed inhibitory effect in the assimilation of this aromatic com- pound. However, one Cr-tolerant strain (Burkholderia cepacia - JT50) got phenol metabolized in the presence of high concentra- tion of K 2 Cr 2 O 7 ( until concentration of 200 μg/ml). Additional in- vestigation of this strain in minimum medium with phenol and chromate indicated that the tolerance mechanism did not involve chemical reduction from Cr 6+ to Cr 3+ , neither any changes in the

The Open Microbiology Journal

Background and Objective: Poly-γ-glutamic acid (γ-PGA) is a constituent of the Bacillus anthracis... more Background and Objective: Poly-γ-glutamic acid (γ-PGA) is a constituent of the Bacillus anthracis capsule and a potential virulence factor of S. epidermidis. In this study, a methodology for the isolation, purification and quantification of γ-PGA in the isolates was adapted. In addition, the fate of the produced γ-PGA and its antiphagocytic activity were investigated. Methods: The capB gene was investigated by the PCR method in 50 isolates of S. epidermidis. A modified methodology was used for the extraction, purification, and quantification of γ-PGA using Cetyltrimethylammonium Bromide (CTAB) solution. The fate of γ-PGA was determined in Tryptic Soy Broth (TSB) medium, as well as the effect of ethanol, NaCl and KCl on the induction of the polymer production. The ability of neutrophils to phagocyte both FITC-labeled latex particles in the presence of free γ-PGA and S. epidermidis with and without anchored γ-PGA was evaluated by cytometry. Results: The production of γ-PGA was detecte...

The open microbiology journal, 2017

Staphylococcus aureus is an important pathogen and a frequent cause of infections associated with... more Staphylococcus aureus is an important pathogen and a frequent cause of infections associated with biofilm production in implantable medical devices. Biofilm production can be induced by sub-inhibitory concentrations (sub-MICs) of certain antibiotics, but few studies have researched this occurrence in S. aureus. In this study, we investigated the effect of sub-MICs of rifampicin and minocycline on biofilm production by five clinical and five non-clinical S. aureus isolates. Microtiter Plate assay and Congo Red Agar Test were used to analyze the biofilm production. The biofilm composition was evaluated by the detachment assay with sodium metaperiodate and proteinase K. Rifampicin sub-MICs induced very high biofilm formation in seven isolates that were non-producers in Tryptic Soy Broth. In one producer isolate, the biofilm formation level was not affected by sub-MICs of this drug. Sub-MICs of minocycline did not induce biofilm production in all isolates tested and in two producer isol...

Clinical …, 2008

This work aimed to evaluate immune events in HIV-1-exposed uninfected neonates born from mothers ... more This work aimed to evaluate immune events in HIV-1-exposed uninfected neonates born from mothers who control (G1) or not (G2) the plasma viral load, using unexposed neonates as controls. Cord blood from each neonate was collected, plasma and mononuclear cells ...

Among these "non-antibiotics", most studies have focused on NSAIDs, drugs thatin addition to anti... more Among these "non-antibiotics", most studies have focused on NSAIDs, drugs thatin addition to anti-inflammatory actionhave analgesic and antipyretic properties. These drugs are among the most widely used in the

International Journal of Microbiology

Staphylococcus aureus is a pathogen commonly resistant to antibiotics. Biofilm formation is one o... more Staphylococcus aureus is a pathogen commonly resistant to antibiotics. Biofilm formation is one of the important factors related to its virulence. Non-antibiotics drugs, such as nonsteroidal anti-inflammatory agents (NSAIDs), have been studied as an alternative for treating infections by multiresistant pathogens and biofilm-associated infections. In this study, the effects of NSAID sodium diclofenac on growth inhibition and biofilm formation of S. aureus were evaluated. The minimum inhibitory concentration (MIC) of diclofenac for fifty isolates ranged from 200 to 400 μg/mL. Diclofenac sub-MICs induced biofilm in 32.3% of biofilm-negative strains in tryptic soy broth. All biofilms induced by the drug showed a PIA- (polysaccharide intercellular adhesion-) independent composition, and the scanning electron microscopy showed that the induced biofilm presented a very discrete matrix. The combination of diclofenac with rifampicin sub-MICs induced strong production of PIA-dependent biofilm...

African Journal of Microbiology Research, Apr 8, 2015

Staphylococcus epidermidis is considered as the main infectious agent associated with implanted m... more Staphylococcus epidermidis is considered as the main infectious agent associated with implanted medical devices. This study determined biofilm production and composition, pulsed-field gel electrophoresis (PFGE) profile, antimicrobial susceptibility and presence of virulence-related genes (ica operon, aap, bhp, embp, capB and IS256 transposase) in 49 clinical isolates of S. epidermidis. Twenty-five isolates (51%) were classified as biofilm producers in microtiter plate (MTP) assay. In Congo red assay (CRA) test, 14 (29%) showed positive reaction and three (6%) had indeterminate reaction, all were biofilmproducers in MTP assay. Fourteen isolates with positive reaction in CRA test had the chemical nature of biofilm determined as polysaccharide, had the ica operon (PIA-dependent producers) and the majority was strong biofilm producer. Eight biofilm producer isolates showed negative reaction in CRA test and the chemical nature of their biofilm was proteinaceous (PIA-independent producers). Antimicrobial resistance rates were generally higher in biofilm producers and resistance to beta-lactams ranged from 82-96%, while 61% of the isolates were multidrug resistant (≥ 10 drugs). Resistance to daptomycin, quinupristin/dalfopristin, rifampin and trimethoprim/sulfamethoxazole was observed only in PIAdependent isolates, while the resistance to gentamicin was present in all PIA-independent isolates and in just 53% of PIA-dependent of isolates. The most prevalent virulence-related genes were capB (80%) and embp (67%); the other genes were less frequent: ica operon (41%), aap (31%), IS256 transposase (22%) and bhp (10%). The presence of ica operon and IS256 transposase gene showed significant association with biofilm production and strong biofilm production. Moreover, these isolates presented significant higher resistance to levofloxacin, moxifloxacin, rifampin and trimethoprim/sulfamethoxazole. PFGE analysis showed 23 profiles, having the prevalent type 15 isolates. Of these, seven were PIAindependent biofilm producers and just one was PIA-dependent producer, unlike what was observed in other studies, where isolates of prevalent profiles were PIA-dependent biofilm producers.

Environmental Toxicology & Water Quality, 1993

Escherichia coli isolated from the intestinal tract of marine fish captured along polluted beache... more Escherichia coli isolated from the intestinal tract of marine fish captured along polluted beaches of the city of Rio de Janeiro, Brazil, were investigated in terms of resistance to seven antibiotics and to four heavy metals. Approximately 40% of the strains were resistant to one or more antibiotics, with predominance of mono- and biresistance. Overall resistance to heavy metals was 70.7%, and exclusive resistance to these elements was more elevated than resistance to antibiotics only. Resistance to mercury was closely associated with resistance to antibiotics and with multiple resistance in particular. Most of the strains analyzed transferred resistance determinants to standard receptor strains during conjugation, the phenomenon being particularly outstanding for the transfer of the copper marker. The epidemiological and ecological aspects of the results obtained are discussed. © 1993 John Wiley & Sons, Inc.

Brazilian Journal of Microbiology, 2012

Samples of sewage from a university hospital and a chemistry technical school were analysed for t... more Samples of sewage from a university hospital and a chemistry technical school were analysed for the percentage of bacterial tolerance to chromium (Cr), silver (Ag) and mercury (Hg). Additionally, we investigated the effect of these metals on pigmentation and on some enzymatic activities of the metal tolerant strains isolated, as well as antimicrobial resistance in some metal tolerant Enterobacteriaceae strains. Tolerance to Cr was observed mainly in Gram positive bacteria while in the case of Ag and Hg the tolerant bacteria were predominately Gram negative. Hg was the metal for which the percentage of tolerance was significantly higher, especially in samples from the hospital sewage (4.1%). Mercury also had the most discernible effect on color of the colonies. Considering the effect of metals on the respiratory enzymes, one strain of Ag-tolerant Bacillus sp. and one of Hg-tolerant P. aeruginosa were unable to produce oxidase in the presence of Ag and Hg, respectively, while the expression of gelatinase was largely inhibited in various Gram negative strains (66% by Cr). Drug resistance in Hg-tolerant Enterobacteriaceae strains isolated from the university hospital sewage was greater than 80%, with prevalence of multiple resistance, while the Agtolerant strains from the same source showed about 34% of resistance, with the predominance of monoresistance. Our results showed that, despite the ability of metal tolerant strains to survive and grow in the presence of these elements, the interactions with these metals may result in metabolic or phisiological changes in this group of bacteria.

Strains of Cr-tolerant or Hg-tolerant Gram-negative bacteria were isolated from Chemistry School&... more Strains of Cr-tolerant or Hg-tolerant Gram-negative bacteria were isolated from Chemistry School's sewage water and these were studied in relation to their ability to use phenol as sole carbon source in the presence of K2Cr2O7 and HgCl2. These metals showed inhibitory effect in the assimilation of this aromatic com- pound. However, one Cr-tolerant strain (Burkholderia cepacia - JT50) got phenol metabolized in the presence of high concentra- tion of K 2 Cr 2 O 7 ( until concentration of 200 μg/ml). Additional in- vestigation of this strain in minimum medium with phenol and chromate indicated that the tolerance mechanism did not involve chemical reduction from Cr 6+ to Cr 3+ , neither any changes in the

The Open Microbiology Journal

Background and Objective: Poly-γ-glutamic acid (γ-PGA) is a constituent of the Bacillus anthracis... more Background and Objective: Poly-γ-glutamic acid (γ-PGA) is a constituent of the Bacillus anthracis capsule and a potential virulence factor of S. epidermidis. In this study, a methodology for the isolation, purification and quantification of γ-PGA in the isolates was adapted. In addition, the fate of the produced γ-PGA and its antiphagocytic activity were investigated. Methods: The capB gene was investigated by the PCR method in 50 isolates of S. epidermidis. A modified methodology was used for the extraction, purification, and quantification of γ-PGA using Cetyltrimethylammonium Bromide (CTAB) solution. The fate of γ-PGA was determined in Tryptic Soy Broth (TSB) medium, as well as the effect of ethanol, NaCl and KCl on the induction of the polymer production. The ability of neutrophils to phagocyte both FITC-labeled latex particles in the presence of free γ-PGA and S. epidermidis with and without anchored γ-PGA was evaluated by cytometry. Results: The production of γ-PGA was detecte...

The open microbiology journal, 2017

Staphylococcus aureus is an important pathogen and a frequent cause of infections associated with... more Staphylococcus aureus is an important pathogen and a frequent cause of infections associated with biofilm production in implantable medical devices. Biofilm production can be induced by sub-inhibitory concentrations (sub-MICs) of certain antibiotics, but few studies have researched this occurrence in S. aureus. In this study, we investigated the effect of sub-MICs of rifampicin and minocycline on biofilm production by five clinical and five non-clinical S. aureus isolates. Microtiter Plate assay and Congo Red Agar Test were used to analyze the biofilm production. The biofilm composition was evaluated by the detachment assay with sodium metaperiodate and proteinase K. Rifampicin sub-MICs induced very high biofilm formation in seven isolates that were non-producers in Tryptic Soy Broth. In one producer isolate, the biofilm formation level was not affected by sub-MICs of this drug. Sub-MICs of minocycline did not induce biofilm production in all isolates tested and in two producer isol...

Clinical …, 2008

This work aimed to evaluate immune events in HIV-1-exposed uninfected neonates born from mothers ... more This work aimed to evaluate immune events in HIV-1-exposed uninfected neonates born from mothers who control (G1) or not (G2) the plasma viral load, using unexposed neonates as controls. Cord blood from each neonate was collected, plasma and mononuclear cells ...

Among these "non-antibiotics", most studies have focused on NSAIDs, drugs thatin addition to anti... more Among these "non-antibiotics", most studies have focused on NSAIDs, drugs thatin addition to anti-inflammatory actionhave analgesic and antipyretic properties. These drugs are among the most widely used in the

International Journal of Microbiology

Staphylococcus aureus is a pathogen commonly resistant to antibiotics. Biofilm formation is one o... more Staphylococcus aureus is a pathogen commonly resistant to antibiotics. Biofilm formation is one of the important factors related to its virulence. Non-antibiotics drugs, such as nonsteroidal anti-inflammatory agents (NSAIDs), have been studied as an alternative for treating infections by multiresistant pathogens and biofilm-associated infections. In this study, the effects of NSAID sodium diclofenac on growth inhibition and biofilm formation of S. aureus were evaluated. The minimum inhibitory concentration (MIC) of diclofenac for fifty isolates ranged from 200 to 400 μg/mL. Diclofenac sub-MICs induced biofilm in 32.3% of biofilm-negative strains in tryptic soy broth. All biofilms induced by the drug showed a PIA- (polysaccharide intercellular adhesion-) independent composition, and the scanning electron microscopy showed that the induced biofilm presented a very discrete matrix. The combination of diclofenac with rifampicin sub-MICs induced strong production of PIA-dependent biofilm...