Comparative study of Staphylococcus aureus from burn patients and healthcare workers in a burn center, Yazd, Iran.

Healthcare workers (HCWs) are proposed as the potential source of transmission of Staphylococcus aureus to hospitalized patients, especially in burn units. This study aimed to investigate S. aureus from burn wound infections and those from the nose of HCWs in terms of antibiotic resistance, the presence of Panton-Valentine leucocidin-encoding gene (pvl) and the arginine catabolic mobile element (ACME), and the ability for biofilm formation. Also, the genetic diversity of isolates was assessed using staphylococcal protein A (spa) typing and staphylococcal cassette chromosome mec (SCCmec) typing. Overall, regarding the studied factors, significant differences were found neither between isolates from patients and HCWs nor between methicillin-resistant and methicillin-susceptible isolates (except for multidrug resistance which was significantly higher in MRSA). The most frequent SCCmec types were type I and III. ACME-arcA was only detected in isolates from patients and similarly the presence of ACME-opp3 was the most prevalent in this group. The presence of common clonal complexes among patient isolates and more importantly between isolates from patients and HCWs is warning. The high prevalence of virulence factors, both in MRSA and MSSA, emphasizes the importance of MSSA in burn centers. Finding no significant difference in the presence of virulence-associated factors between isolates from patients and HCWs demonstrates the need to take HCWs into account as important reservoirs.

High-Level Resistance to Erythromycin and Tetracycline and Dissemination of Resistance Determinants among Clinical Enterococci in Iran.

OBJECTIVES: The purpose of this study was to investigate the distribution pattern of genes responsible for erythromycin and tetracycline resistance and their association with resistance phenotypes in enterococcus isolates. MATERIALS AND METHODS: Eighty-six Enterococcus faecalis and 26 E. faecium isolates were collected from 2 hospitals in Kerman, Iran. Minimum inhibitory concentration of erythromycin and tetra-cycline was determined and then genes encoding resistance to erythromycin - erm (A-C), mef, and msr - and tetracycline - tet (M), tet (O), tet (S), tet (K), and tet (L) - were investigated. RESULTS: In all resistant isolates (n = 72, 64%), high-level resistance to both tested antibiotics was found. The most prevalent erm gene was erm (B) (77.7%), followed by erm (A) (15.2%) and erm (C) (8.3%). Genes mediating erythromycin efflux were detected in 70.8% (mef) and 9.7% (msr) of resistant isolates. Regarding tetracycline, tet (M) was detected at the highest rate (50%), followed by tet (O) (31%) and tet (S) (11%). Export of tetracycline was found in 31% (tet (K)) and 12% (tet (L)) of isolates. CONCLUSION: A high prevalence of high-level resistance to both erythromycin and tetracycline was documented. Alterations at the ribosomal level was more frequently detected in erythromycin and tetracycline resistance than efflux systems. Concurrent resistance mechanisms were more involved in resistance to erythromycin than tetracycline.

Co-Incidence of Type II Topoisomerase Mutations and Efflux Expression in High Fluoroquinolone Resistant Enterococcus faecalis Isolated from Urinary Tract Infections.

INTRODUCTION: Enterococcus faecalis is one of the most common pathogens in urinary tract infections (UTIs). Fluoroquinolones have been frequently used to treat E. faecalis UTIs, and the emergence of fluoroquinolone-resistant E. faecalis strains has recently been reported in several countries. This study aimed to elucidate the mechanisms involved in fluoroquinolone resistance in clinical E. faecalis isolates by analyzing mutations in quinolone- resistance-determining regions (QRDRs) of gyrA and parC and investigating the role of some efflux pumps. METHODS: In total, 70 clinical E. faecalis isolates collected from UTIs were identified by phenotypic and genotypic methods. Antimicrobial susceptibility testing was performed and multidrug-resistant (including ciprofloxacin resistant) isolates were studied for minimum inhibitory concentrations to ciprofloxacin, levofloxacin, and ofloxacin. In the following, mutations in QRDRs of gyrA and parC and expression of EfrA, EfrB, and EmeA efflux pumps were investigated in 20 high-level ciprofloxacin resistant and two ciprofloxacin susceptible isolates. RESULTS: High-level resistance to ciprofloxacin was detected in 97.5% of isolates. Sequencing of QRDRs revealed that 65% and 75% of isolates carried mutations in gyrA and parC, respectively. The presence of efflux genes was detected in all studied isolates, but expression of efrA, emeA, and efrB was demonstrated in 50%, 40%, and 30% of resistant isolates, respectively. Neither QRDR mutation nor the expression of efflux genes showed any significant association with MIC. CONCLUSION: Co-incidence of mutation and efflux gene expression in more than half of isolates (13/20) suggests that both mechanisms may play a role in fluoroquinolone resistance. The other unknown mechanisms including different efflux pumps and probably other QRDRs mutations may contribute to fluoroquinolone resistance in E. faecalis.