Vancomycin-heteroresistant phenotype in invasive methicillin-resistant isolates belonging to type 041

M. Monaco (1) , A. Sanchini (1) , H. Grundmann (2, 3) , A. Pantosti (1)

1 Department of Infectious, Parasitic and Immune-Mediated Diseases [Rome]
2 National Institute for Public Health and the Environment
3 Department of Medical Microbiology

The aim of this study was to characterise invasive methicillin-susceptible (MSSA) and methicillin-resistant (MRSA) strains from Italy and to investigate the presence of heteroresistant vancomycin-intermediate (h-VISA). Eighty-two MSSA and 66 MRSA strains obtained from 19 laboratories were submitted to in vitro susceptibility testing; MRSA strains were also analysed by the macro Etest (MET) and vancomycin population analysis profiles (PAP) to detect the presence of h-VISA. Genotyping included the detection of locus, SCC typing, typing and multilocus sequence typing (MLST). By Etest, 66% of all isolates showed a minimum inhibitory concentration (MIC) ≥1.5 μg/ml and two MRSA strains were categorised as VISA (MIC = 3 μg/ml). Twelve MRSA strains were positive by MET; of these, 9 (14% of all MRSA) were confirmed as h-VISA by PAP. MRSA strains were assigned to 14 types, with t001, t008 and t041 including 77% of the isolates. The most common type, t041, characterised as ST228/273-MRSA-I (CC5) and comprising 24 isolates, included one VISA and eight h-VISA. This is the first description of a close association between h-VISA and t041, a type common in Italy and in other European countries, that highlights the importance of molecular typing to identify clones of special clinical relevance.

Mots clés: Life Sciences

M. Monaco, A. Sanchini, H. Grundmann, A. Pantosti. Vancomycin-heteroresistant phenotype in invasive methicillin-resistant isolates belonging to type 041. European Journal of Clinical Microbiology and Infectious Diseases, 2010, 29 (7), pp.771-777. ⟨10.1007/s10096-010-0922-2⟩. ⟨hal-00586598⟩