Methicillin-resistant Staphylococcus aureus (MRSA) in the community – laboratory based study

Objective To determine the occurrence and antibiotic resistance of community-acquired methicillin-resistant Staphylococcus aureus (MRSA) isolates. Methods used In 2003-2005, consecutive samples of nasal, throat, eye, ear and genitourinary tract swabs, swabs of wound infections and soft and skin tissue infections and samples of sputum obtained from outpatients submitted to the Laboratory with clinical indications were analyzed for the presence of Staphylococcus aureus. The disc diffusion method using Mueller-Hinton agar (Oxoid, Besingstoke, UK) was used to test against nine antimicrobials. Oxacillin-resistance was confirmed by E-test (AB Biodisc, Solna, Sweden). Results A total of 1583 (11.3%) nonduplicate S. aureus isolated from 13 937 samples. MRSA was detected in 63 (4.1%) of S. aureus isolates. MRSA isolates more frequently from infected genitourinary tract and wounds than other sites (p<0.0001). The patients in both age groups ≥65 and 0-6 years of age were more frequently infected with MRSA than patients of other age groups (p=0.02). Statistically significant differences in susceptibility rates between MSSA and MRSA isolates were found for all antibiotic tested (p=0.0053 to p<0.000). MRSA isolates were more frequently multidrug resistant (MDR) than MSSA isolates (p=0.0009). SCCmec type IV or V phenotype was detected in 30 (47.6%) of MRSA isolates. Conclusion Although low MRSA prevalence was noted, the presence of SCCmec type IV/V phenotypes in the community is of particular concern. Effective control of dissemination of MRSA throughout the community will likely require effective control and monitoring of nosocomial MRSA transmission.