Management of serious meticillin-resistant infections: what are the limits?

Ian M. Gould (1) , Roberto Cauda (2) , Silvano Esposito (3) , Francesco Gudiol (4) , Teresita Mazzei (5) , Javier Garau (6)

1 Department of Medical Microbiology
2 Departments of Infectious Diseases
3 Department of Infectious Diseases
4 Bellvitge University Hospital = Bellvitge Hospital Universitari
5 Department of Preclinical and Clinical Pharmacology
6 Department of Medicine

Severe (life-threatening) meticillin-resistant (MRSA) infection continues to be treated with vancomycin despite accumulating evidence of poor outcome, increasing resistance and unachievable pharmacokinetic/pharmacodynamic (PK/PD) targets. The minimum inhibitory concentration (MIC) susceptibility breakpoint for vancomycin was recently reduced to 2mg/L. Whilst the great majority of clinical isolates are thus still classified as susceptible, the available clinical evidence argues for a method-dependent breakpoint of 0.5mg/L (broth dilution) or 1.0mg/L (Etest), which would classify many strains as resistant, or at best intermediate. However, automated susceptibility testing systems are not currently capable of performing accurately at this low level, and such low breakpoints are unsatisfactory because the poor reproducibility of tests (plus or minus one doubling dilution) results in a critical non-reproducibility around the modal MIC of 1mg/L described in most published data. Therefore, vancomycin should be used with caution in severe (life-threatening) staphylococcal disease and the MIC should always be reported by method. Daptomycin is generally preferred for bacteraemia/endocarditis and linezolid for pneumonia. Better outcome data for vancomycin, based on achievable PK/PD targets and using robust MIC tests, are urgently required.

Mots clés: MRSA treatment; Antibiotics; MIC drift

Domaines: Microbiologie et Parasitologie

Ian M. Gould, Roberto Cauda, Silvano Esposito, Francesco Gudiol, Teresita Mazzei, et al.. Management of serious meticillin-resistant infections: what are the limits?. International Journal of Antimicrobial Agents, 2011, 37 (3), pp.202. ⟨10.1016/j.ijantimicag.2010.10.030⟩. ⟨hal-00671244⟩