DISTRIBUTION OF GENES ENCODING ERYTHROMYCIN RIBOSOMAL METHYLASES AND MACROLIDE EFFLUX PUMP IN METHICILLIN RESISTANT STAPHYLOCOCCUS AUREUS ISOLATES FROM TERTIARY CARE HOSPITALS IN TAMIL NADU.
Stalin M., Saravanan M. and Padma Krishnan*
ABSTRACT
The increasing frequency of the infections with MRSA and the changing drug susceptibility pattern have led to renewed interest in the use of Macrolide Lincosamide Streptogramin-B (MLSB) antibiotic to treat these infections. Resistance to macrolide and lincosamide is prevalent among staphylococci in recent days. Hence this study was aimed to undertake the detection of resistance determinants of macrolide and methicillin resistant S. aureus isolates. A total of 237 Staphylococcus aureus isolates collected during 2013-2014, from various tertiary care hospitals were included in this study. MLSBi (inducible clindamycin resistance) was screened by using D- test. Confirmation of MRSA was done by molecular detection of mecA and femA gene. Detection of erythromycin resistance genes (ermA, ermC) and macrolide efflux (msrA) resistance genes was done by multiplex PCR. Of the 237 Staphylococcus aureus isolates, 150 (63%) expressed resistance to erythromycin, 46 isolates were MSSA and 104 were MRSA. Our study showed MLSBi in 35% of MRSA and 15% of MSSA. Among MRSA, the most prevalent resistant determinant was ermA (22%), ermC in 9%, msrA in 16% of isolates, whereas 20% of isolates harboured multiple resistance mechanisms. Among MSSA, ermA gene was found in 22% of isolates, ermC in 9%, msrA in 4% of isolates, while 9% of isolates harboured multiple resistance mechanisms. In conclusion, 20% of isolates were detected in combination of erm genes with other resistance gene msrA. Though ermA gene was most prevalent, but isolates exhibits multiple resistance mechanism was found to be high in our study, which was less frequently reported.
Keywords: (D-Test, MLSB, msrA gene and erm gene).
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