Detection of Mupirocin Resistance in Methicillin- Resistant Staphylococcus aureus Isolates in an Egyptian Hospital

Background: Nasal carriage of methicillin-resistant Staphylococcus aureus (MRSA) can be eradicated by topical mupirocin application. Mupirocin resistance, on the other hand, is becoming more widespread. Objective: The present work aims to compare conventional and molecular approaches to detect the prevalence of mupirocin resistance in MRSA isolates from clinical and nasal samples, as well as to investigate their susceptibility to other antibiotics. Methodology: Our study included 60 MRSA non-duplicate isolates, 14 from surgical wounds, 16 from urinary tract infections from patients hospitalized to Suez- Canal University Hospital in Ismailia, Egypt, and 30 nasal swabs from health care workers. The minimum inhibitory concentrations (MICs) for MRSA isolates to mupirocin were determined using the E-test method, and PCR targeting the mupA gene was performed. Results: Six isolates out of 60 MRSA isolates (10%) showed high-level mupirocin resistance, while just one strain (1.6%) showed low-level mupirocin resistance. Four of the six MRSA isolates with high levels of mupirocin resistance carried the mupA gene. All seven mupirocin-resistant isolates (11.6%) were isolated from nasal swabs. MRSA strains resistant to mupirocin were more resistant to tetracycline, chloramphenicol, gentamycin, ciprofloxacin, and trimethoprim-sulfamethoxazole than mupirocin-susceptible ones. Conclusion: The high prevalence of mupirocin resistance in MRSA strains at our hospital is alarming. As a result, frequent testing of MRSA for mupirocin resistance is recommended even in settings where mupirocin is not used prophylactically.