METHODS: Clinical specimens from three Kathmandu hospitals were processed and S. aureus was identified using conventional microbiological procedures. MRSA was phenotypically identified with cefoxitin (30µg) disc diffusion, while vancomycin susceptibility was assessed using the Ezy MICTM stripes. The mecA and vanA genes were detected by polymerase chain reaction (PCR).
RESULTS: Out of 266 S. aureus samples from various clinical specimen subjected for analysis, 77 (28.9%) were found methicillin-resistant (MRSA) and 10 (3.8%) were observed vancomycin-resistant (VRSA). Vancomycin resistant isolates showed a significant correlation between resistance to ampicillin, chloramphenicol, and cefoxitin. The mecA gene was found in 39 of the MRSA isolates, having 50.64% of MRSA cases, while the vanA gene was detected in 4 of the VRSA cases, constituting 40% of VRSA occurrences.
CONCLUSIONS: The strains with higher vancomycin minimum inhibitory concentration values (≥ 1.5 μg/ml) displayed increased resistance rates to various antibiotics compared to strains with lower minimum inhibitory concentration values (< 1.5 μg/ml). The presence of vanA genes was strongly associated (100%) with vancomycin resistance, while the 10.3% mecA gene was identified from MRSA having resistance towards vancomycin also.
RESULT: The recipient transconjugants were resistant to erythromycin, cefpodoxime and were mecA positive. PCR amplification of mecA after mix culture plating on Luria Bertani agar containing 100 μg/mL showed that 75% of the donor and 58.3% of the recipient transconjugants were mecA positive. Additionally, 61.5% of both the donor cells and recipient transconjugants were mecA positive, while 46.2% and 41.75% of both donor and recipient transconjugants were mecA positive on LB agar containing 50 μg/mL and 30 μg/mL respectively.
CONCLUSION: In this study, the direction of transfer of phenotypic resistance as well as mecA was observed to have occurred from the donor to the recipient strains. This study affirmed the importance of horizontal transfer events in the dissemination of antibiotics resistance among different strains of MRSA.
METHODS: MRSA strains were collected and molecularly typed by pulsed-field gel electrophoresis (PFGE).
RESULTS: PFGE typing on 180 MRSA isolated in UKMMC identified 5 pulsotypes (A-E) and 6 singletons, where pulsotypes B and C were suspected to be divergent clones originating from a single ancestor. This study also showed that most MRSA strains were isolated from swab (119 isolates), followed by blood (22 isolates), tracheal aspirate (11 isolates) and sputum (10 isolates). On the other hand, urine and bone isolates were less, which were 4 and 1 isolates, respectively. The distribution of different pulsotypes of MRSA among wards suggested that MRSA was communicated in surgical and medical wards in UKMMC, with pulsotype B MRSA as the dominant strain. Besides, it was found that most deceased patients were infected by pulsotype B MRSA, however, no particular pulsotype could be associated with patient age, underlying disease, or ward of admittance.
CONCLUSIONS: Five pulsotypes of MRSA and 6 singletons were identified, with pulsotype B MRSA as the endemic strains circulating in these wards, which is useful in establishment of preventive measures against MRSA transmission.