agrDysfunction Affects Staphylococcal Cassette ChromosomemecType-Dependent Clinical Outcomes in Methicillin-Resistant Staphylococcus aureus Bacteremia
ABSTRACTStaphylococcal cassette chromosomemecelement (SCCmec) type-dependent clinical outcomes may vary due to geographical variation in the presence of virulence determinants. We compared the microbiological factors and mortality attributed to methicillin-resistantStaphylococcus aureus(MRSA) bacteremia between SCCmectypes II/III and type IV. All episodes of MRSA bacteremia in a tertiary-care hospital (South Korea) over a 4.5-year period were reviewed. We studied the microbiological factors associated with all blood MRSA isolates, includingspatype,agrtype,agrdysfunction, and the genes for Panton-Valentine leukocidin (PVL) and phenol-soluble modulin (PSM)-mec, in addition to SCCmectype. Of 195 cases, 137 involved SCCmectypes II/III, and 58 involved type IV. The mortality attributed to MRSA bacteremia was less frequent among the SCCmectype IV (5/58) than that among types II/III (39/137,P= 0.002). This difference remained significant when adjusted for clinical factors (adjusted odds ratio [aOR], 0.14; 95% confidence interval [CI], 0.04 to 0.49;P= 0.002). Of the microbiological factors tested,agrdysfunction was the only significant factor that showed different positivity between the SCCmectypes, and it was independently associated with MRSA bacteremia-attributed mortality (aOR, 4.71; 95% CI, 1.72 to 12.92;P= 0.003). SCCmectype IV is associated with lower MRSA bacteremia-attributed mortality than are types II/III, which might be explained by the high rate ofagrdysfunction in SCCmectypes II/III in South Korea.