Differences in antibiotic resistance profiles of methicillin-susceptible and –resistant Staphylococcus aureus isolated from the teaching hospital in Kuala Lumpur, Malaysia

In general, methicillin-resistant Staphylococcus aureus (MRSA) is more resistant to multiple antibiotics than methicillin-susceptible S. aureus (MSSA). However, some studies have been inconclusive on antibiotic resistance patterns in MSSA and MRSA. This study’s objectives were to compare antibiotic resistance patterns of MSSA and MRSA, and to type staphylococcal cassette chromosome mec (SCCmec) in MRSA isolates. S. aureus (MRSA=50; MSSA=50) isolates were collected from the primary teaching hospital in Kuala Lumpur, Malaysia. Antibiotic susceptibility test and amplification of SCCmec elements and antibiotic resistance genes were conducted. MRSA had significantly higher resistance to clindamycin, erythromycin, and ciprofloxacin (P < 0.001) than MSSA, while MSSA had higher resistance to tetracycline than MRSA (P < 0.05). Resistance to gentamicin, fusidic acid, rifampicin, and mupirocin was low in both groups. Multidrug resistance was observed in 14% of MSSA and 66% of MRSA. Remarkably, SCCmec type IV was dominant in MRSA (96%) isolated from this study. All MSSA (5/5) and 27/31 of MRSA harbored ermC, respectively. ermA and AacA-D were not observed in both groups. One MSSA isolate harbored tetK, while tetM was not detected. This study reveals differences in the antibiotic resistance pattern of MSSA and MRSA. The emergence of multidrug resistance in MSSA warrants further surveillance.