Emergence of a community-associated methicillin-resistant Staphylococcus aureus with unique resistance profile in Southwest of Nigeria

Pheno-, genotypic and toxin gene analysis has not been done yet all in one for Nigerian Staphylococcus aureus population. This study provides a comprehensive overview on the molecular epidemiology and genetic diversity of S. aureus at the largest university clinic in Ibadan, Nigeria. At the University Teaching Hospital in Ibadan, Nigeria, out of 1300 patients’ clinical samples 346 non-duplicate S. aureus isolates were obtained during the 1-year surveillance in 2007. All isolates underwent antibiotic susceptibility testing, toxin gene analysis, MLST (multilocus sequence typing), agr group and spa typing. And for MRSA SCCmec typing was performed. 20.23% of the 346 isolates were methicillin-resistant. 33 patients’ isolates (47.15%) fulfilled the definition criteria for CA-MRSA according to the review of the medical charts. The majority of MRSA strains analyzed were isolated from surgical and paediatric patients. The commonest types of infection identified with MRSA were surgical site infections (>70%) whereas for CA-MRSA were conjunctivitis and otitis in 19 patients (57.6%) and accidental skin and subcutaneous tissue infection in 14 patients (42.4 %). The MSSA strains (ST1, ST5, ST15, ST7, ST8, ST25, ST30, ST72, ST80, ST121 and ST508) were heterogeneous by phenoand genotypic analysis. The first report and genetic analyses of PVL-positive ST88 strain (agr III, SCCmec IV) in Nigeria is shown in this study. ST88 was resistant to trimethoprim-sulfamethoxazole besides to penicillin and oxacillin. CA-MRSA infections are rapidly increasing among young patients with ophthalmologic and auricular infections. Urban regions of lower socioeconomic status and evidence of overcrowding appear to be at higher risk for the emergence of this clone.