Search

Over-expression of alpha-phenol-soluble modulins (PSMs) results in high virulence of community-associated methicillin-resistant Staphylococcus aureus (MRSA). The psm-mec gene, located in the mobile genetic element SCCmec-II, suppresses PSMαs production. Fifty-two patients with MRSA bacteraemia were enrolled. MRSA isolates were evaluated with regard to the psm-mec gene sequence, bacterial virulence, and the minimum inhibitory concentration (MIC) of vancomycin and teicoplanin. Fifty-one MRSA isolates were classified as SCCmec-II, and 10 had one point mutation in the psm-mec promoter. We compared clinical characteristics and outcomes between mutant MRSA and wild-type MRSA. Production of PSMα3 in mutant MRSA was significantly increased, but biofilm formation was suppressed. Wild-type MRSA caused more catheter-related bloodstream infections (30/41 vs. 3/10, p 0.0028), whereas mutant MRSA formed more deep abscesses (4/10 vs. 3/41, p 0.035). Bacteraemia caused by mutant MRSA was associated with reduced 30-day mortality (1/10 vs. 13/41, p 0.25), although this difference was not significant. The MIC90 of teicoplanin was higher for wild-type MRSA (1.5 mg/L vs. 1 mg/L), but the MIC of vancomycin was not different between the two groups. The 30-day mortality of MRSA with a high MIC of teicoplanin (≥1.5 mg/L) was higher than that of strains with a lower MIC (≤0.75 mg/L) (6/10 vs. 6/33, p 0.017). Mutation of the psm-mec promoter contributes to virulence of SCCmec-II MRSA, and the product of psm-mec may determine the clinical characteristics of bacteraemia caused by SCCmec-II MRSA, but it does not affect mortality., (© 2014 The Authors Clinical Microbiology and Infection © 2014 European Society of Clinical Microbiology and Infectious Diseases.)

We report a case of epidural abscess caused by community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) strain USA300 in a previously healthy 25-year-old American woman who lived in Japan for more than 1 year. She started to complain of severe headache that continued for about 10 days after improvement of subcutaneous abscesses caused by MRSA. Computed tomography (CT) and magnetic resonance imaging (MRI) showed epidural abscess. As epidural abscess was not improved by treatment with vancomycin and ceftriaxone, craniotomy and drainage were performed, and the severe headache disappeared. Characteristics of the MRSA strain isolated from the abscess were identical to those of strain USA300; multilocus sequence typing sequence type 8, staphylococcal cassette chromosome mec type IVa, Panton-Valentine leukocidin positive, arginine catabolic mobile element positive, and pulsed-field gel electrophoresis type USA300. This may be the first report of epidural abscess caused by USA300 strain in Japan. Because CA-MRSA strains, including USA300, have begun to spread in Japan, epidural abscess should be taken into account in the diagnosis of previously healthy patients with persistent headache accompanied by skin lesions.