Resistance to methicillin and virulence of Staphylococcus aureus strains in bacteriemic cancer patients.

Abstract

To estimate the relation between resistance to methicillin and virulence in strains of Staph. aureus by estimating the survival at day 30. Case control analysis. Inpatients at a major Cancer Referral Center. 21 patients with methicillin-resistant Staph. aureus (MRSA) bactaeremia and 45 patients with methicillin-susceptible Staph. aureus (MSSA) bactaeremia, all treated with vancomycin. Fewer MRSA than MSSA patients were neutropenic (p = 0.04), but more MRSA patients were hospitalized in intensive care units (p = 0.03), had had surgical episodes (p = 0.06). MRSA patients also had more microbiological samples cultured (p = 0.007). The outcome of the bacteriemic episodes in 14 MRSA and 14 MSSA patients matched for these four factors showed that blood cultures from MRSA patients remained positive significantly longer (p = 0.04), but that survival and length of hospital stay were not significantly different. These results do not indicate that methicillin-resistance in Staph. aureus is associated with increased virulence.