Manipal Journal of Medical Sciences


Context: Methicillin resistant Staphylococcus aureus (MRSA) is a nosocomial pathogen, which often exhibits multidrug resistance. It colonizes the anterior nares of humans, from where it can be transmitted to vulnerable individuals, causing life threatening infections. Using various phenotypic and genotypic methods, two types of strains have been identified such as hospital associated MRSA (HA-MRSA) and community associated MRSA (CA-MRSA). Aims: To evaluate the status of MRSA nasal colonization among inpatients of a tertiary care centre and classify them by antibiogram, Panton Valentine leucocidin (PVL) assay and staphylococcal cassette chromosome (SCC) mec typing. Methodology: A hospital based, cross-sectional study was conducted, involving 71 adult inpatients. Nasal swabs were collected and isolates were subjected to biochemical testing to identify Staphylococcus aureus (S. aureus). Antibiotic susceptibility testing, PVL assay, and SCC mec typing were also performed. Statistical analysis was performed using SPSS version 16. Results: Out of 71 nasal swab isolates, 11 were identified as MRSA. All the MRSA were resistant to ampicillin and ciprofloxacin. Erythromycin and clindamycin resistance were noticed in 88.9% and 44.4% of strains, respectively. Inducible clindamycin resistance was detected in two strains by D-Test. All isolates were negative for pvl gene. SCC mec typing revealed four Type-I strains, one Type-II strain and one Type-IV strain. The other five isolates could not be typed with the limited number of primers used in this study. Conclusions: Since majority of the MRSA were likely to be of HA-MRSA type, it is assumed that, the patients would have been colonized with them after hospitalization. This demands the necessity of MRSA screening for health care workers, which ultimately aids in planning strategies to control their outbreaks in health care settings