[Trends in Staphylococcus aureus antimicrobials susceptibilities: is methicillin still a relevant multiresistance...

Recent change was noted in S. aureus epidemiology, especially for none multiresistant methicillinresistant S. aureus (MRSA) and for multiresistant methicillin-susceptible S. aureus (MSSA). So, a six-year retrospective study was conducted to follow trends in antimicrobials resistance and to determine if methicillin remained a relevant multiresistant marker.

All S. aureus isolates (duplicates excluded) isolated between 2001 and 2006 in a French 800-beds-teaching-hospital were included in the study.

Four thousand four hundred and fifty-five isolates providing from 3602 patients were identified between 2001 and 2006. MRSA rate and incidence for 1000 hospitalization-days significantly decreased from 34.7 to 22.6% and 1.3 to 0.6% respectively (p < 0.001). Significant decrease was observed for multiresistant MRSA (72.9 to 46.3%, p < 0.001), while no change was observed for multiresistant MSSA (2.9 to 3.4%). Among the 186 different antibiotic patterns isolated, four MRSA-phenotypes significantly decreased whereas two MSSA-phenotypes significantly increased. The main MRSA phenotype, resistant to kanamycin, tobramycin, macrolides-lincosamides-streptograminesB, and fluoroquinolones, significantly decreased from 11.9 to 5.9% (p < 0.001). Glycopeptide Intermediate S. aureus (GISA) phenotypes disappeared.

At this date, methicillin remains in our institution a relevant marker of multiresistance but trend is changing.