Detection of the agr System and Resistance to Antimicrobials in Biofilm-Producing S. epidermidis.

The ability of Staphylococcus epidermidis to produce virulence factors, such as biofilm, added to its increased resistance to antimicrobials can cause infections that are difficult to treat. Many staphylococcal virulence factors are under the control of the accessory gene regulator (agr). The objective of this study was to establish the agr locus and susceptibility of biofilm-producing S. epidermidis specimens to antimicrobial agents, through PCR reactions, reverse transcription polymerase chain reaction (RT-PCR), and the determination of minimum inhibitory concentration (MIC), and to analyze the clonal profile of 300 strains isolated from blood culture specimens from inpatients at a University Hospital in Brazil, over a 20-year period by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) techniques. The ica operon expression was shown in 83.6% strains, bhp gene in 11.5%, and aap gene in 32.8%. Oxacillin resistance was detected in 90.1%, while 4.9% showed tigecycline resistance, and intermediate resistance to quinupristin/dalfopristin was identified in 0.4%. Clonal profile determination showed 11 clusters, with the ST2 type determined as the major cluster. The S. epidermidis biofilm producer demonstrated a predominance of agr I locus, oxacillin resistance, and SCCmec III as well as the potential dissemination of pathogenic clones in hospital settings over long periods.

Comparative Study Of Genetic Diversity, Virulence Genotype, Biofilm Formation And Antimicrobial Resistance Of Uropathogenic Escherichia coli (UPEC) Isolated From Nosocomial And Community Acquired Urinary Tract Infections.

INTRODUCTION: Escherichia coli is a Gram-negative opportunistic human pathogen, which has aroused considerable medical interest for being involved in cases of urinary tract infection. AIM: Characterize the E. coli isolated both in the hospital and in the community. METHODOLOGY: A total of 200 E. coli isolated in urine samples from hospital and community were evaluated in biofilm formation assay and hydrophobicity MATS method. Antimicrobial susceptibility was performed through agar-diffusion technique. Virulence and ESBL production genes were observed through the polymerase chain reaction amplification of papC, fimH, fliC, kpsMTII, blaTEM, blaCTX-M, blaSHV , and blaOXA. The phylogenetic classification was based on the pattern chuA and yjaA and the region TspE4.C2 by PCR Multiplex. RESULTS: A higher frequency of non-adherent or poorly adherent isolates was observed in the community group. Approximately 85% of the community isolates were distributed in the highest hydrophilicity group (p<0.05). The level of resistant microorganisms was present at the same level in both source (p>0.05). About 14% of the hospital isolates were positive in the ESBL phenotypic detection test (p>0.05). Among the samples, 95% presented ESBL-encoding genes. The predominant phylogenetic group was B2 (78%). Community isolates showed a higher prevalence of virulence genes fimH, papC, and kpsMTII when compared to hospital samples. CONCLUSION: These data confirm the worldwide trend that isolates in the community present sometimes higher levels of virulence and antimicrobial resistance.

Antimicrobial Resistance Profile of Planktonic and Biofilm Cells of Staphylococcus aureus and Coagulase-Negative Staphylococci.

The objective of the present study was to determine the antimicrobial resistance profile of planktonic and biofilm cells of Staphylococcus aureus and coagulase-negative staphylococci (CoNS). Two hundred Staphylococcus spp. strains were studied, including 50 S. aureus and 150 CoNS strains (50 S. epidermidis, 20 S. haemolyticus, 20 S. warneri, 20 S. hominis, 20 S. lugdunensis, and 20 S. saprophyticus). Biofilm formation was investigated by adherence to polystyrene plates. Positive strains were submitted to the broth microdilution method to determine the minimum inhibitory concentration (MIC) for planktonic and biofilm cells and the minimal bactericidal concentration for biofilm cells (MBCB). Forty-nine Staphylococcus spp. strains (14 S. aureus, 13 S. epidermidis, 13 S. saprophyticus, 3 S. haemolyticus, 1 S. hominis, 3 S. warneri, and 2 S. lugdunensis) were biofilm producers. These isolates were evaluated regarding their resistance profile. Determination of planktonic cell MIC identified three (21.4%) S. aureus strains that were resistant to oxacillin and six (42.8%) that were resistant to erythromycin. Among the CoNS, 31 (88.6%) strains were resistant to oxacillin, 14 (40%) to erythromycin, 18 (51.4%) to gentamicin, and 8 (22.8%) to sulfamethoxazole/trimethoprim. None of the planktonic isolates were resistant to vancomycin or linezolid. MICs were 2-, 4-, 8-, and up to 16-fold higher for biofilm cells than for planktonic cells. This observation was more common for vancomycin and erythromycin. The MBCB ranged from 8 to >256 µg/mL for oxacillin, 128 to >128 µg/mL for vancomycin, 256 to >256 µg/mL for erythromycin and gentamicin, >64 µg/mL for linezolid, and 32/608 to >32/608 µg/mL for sulfamethoxazole/trimethoprim. The results showed considerably higher MICs for S. aureus and CoNS biofilm cells compared to planktonic cells. Analysis of MBCM confirmed that even high concentrations of vancomycin were unable to eliminate the biofilms of S. aureus and CoNS species. Linezolid was the most effective drug in inhibiting staphylococci in the biofilm, without an increase in the MIC, when compared to planktonic cells. None of the isolates were resistant to this drug.