Isolation and identification of methicillin-resistant Staphylococcus aureus from students’ coins

Abstract

Methicillin-resistant Staphylococcus aureus (MRSA) is a nosocomial pathogen of increasing risk on community. This study aims at determining the risk of MRSA transfer from coins as silent and underestimated reservoir in community. One hundred swabs from coins were collected from college students in Malaysia. A series of identification and differentiating tests were conducted for precise identification of MRSA bacteria. Moreover, this study compared the efficacy of the different identification tests with gold standard, polymerase chain reaction (PCR) assay. The tests used were tube coagulase, DNase agar test, antibiogram, several routine biochemical identification tests and PCR assays. PCR assay used specific primers for resistance or ID -related genes: mecA, ermA, ermB, ermC, msrA, linA, femA, and nuc genes. A total of 37 bacterial isolates were isolated from college students’ coins; non-PCR assays of identification and resistance detection revealed the presence and spread of MRSA in coins of 2 college students. PCR-amplification of the nuc gene was used as a baseline test to detect S. aureus. PCR showed only one isolate as true MRSA. False positive MRSA by disc diffusion assay might be attributed to low pH and high thymidine content of Muller Hinton agar medium. Collectively, coins proved to be possible source for the transfer of MRSA in community of college students in South East Asia. Moreover, PCR assay for identification of S. aureus resistance proved to be superior on other methods.

Key words: Staphylococcus aureus, MRSA, nail, PCR, resistance.