Usefulness of antimicrobial resistance pattern for detecting PVL- or TSST-1-producing meticillin-resistant Staphylococcus aureus in a French university hospital.

Several recent reports have suggested that community-associated meticillin-resistant Staphylococcus aureus (MRSA) clones, particularly those harbouring genes for Panton-Valentine leukocidin (PVL) or toxic shock syndrome toxin 1 (TSST-1), are increasingly responsible for infections in hospitals. Here, a retrospective study was carried out to investigate whether antimicrobial resistance patterns could be used to detect these pathogens in a French university hospital. Isolates were characterized by antimicrobial susceptibility testing, PCR profiling (PVL genes and tst), PFGE typing and multilocus sequence typing. Demographic and clinical data were collected from all patients. For PVL-positive MRSA, the typical antimicrobial resistance pattern (susceptible to fluoroquinolones, non-susceptible to fusidic acid, kanamycin resistant and susceptible to gentamicin and tobramycin) had a sensitivity of 77.8 % and a positive predictive value (PPV) of 100 %. For tst-positive MRSA, the antimicrobial resistance pattern (susceptible to fluoroquinolones and non-susceptible to fusidic acid) had a sensitivity of 100 % and a PPV of 72.4 %. These results suggest that phenotypic rules based on antimicrobial resistance patterns are potentially useful for the detection of PVL- and tst-positive MRSA isolates.