Heteroresistance to glycopeptides in Italian meticillin-resistant (MRSA) isolates

Floriana Campanile (1) , Sonia Borbone (1) , Marianna Perez (1) , Dafne Bongiorno (1) , Viviana Cafiso (1) , Taschia Bertuccio (1) , Simona Purrello (1) , Daria Nicolosi (1) , Cristina Scuderi (1) , Stefania Stefani (1)

1 Department of Microbiology

The prevalence and molecular characterisation of heteroresistant vancomycin-intermediate (hVISA) strains were determined in a large group of Italian strains isolated between 2005 and mid 2007. Among the 1284 strains isolated from documented infections in hospitalised patients (bloodstream infection, pneumonia, and skin and skin-structure infections), 139 with vancomycin minimum inhibitory concentration (MICs) between 1mg/L and 2mg/L were screened for the presence of hVISA using three different methods and were confirmed by population analysis profile (PAP). Thirty-six hVISA strains (25.9%) were detected. Among the three screening methods used, the macro Etest (MET) demonstrated 100% specificity and 75% sensitivity. hVISA strains were accessory gene regulator () types I and II and belonged to the major nosocomial clones circulating in Italy (ST8, ST239, ST247 and ST228). All strains were susceptible to quinupristin/dalfopristin, linezolid, daptomycin, tigecycline and dalbavancin. In conclusion, we have demonstrated that hVISA isolates are common among MRSA isolates with MICs between 1mg/L and 2mg/L in Italy. MET, with its high sensitivity and specificity, should be used for early detection of hVISA, especially in patients with serious or prolonged infections sustained by MRSA. Finally, the most recent anti-Gram-positive drugs maintained their full spectrum of in vitro activity against these strains.

Mots clés: hVISA; Glycopeptides; MIC creep; MRSA

Floriana Campanile, Sonia Borbone, Marianna Perez, Dafne Bongiorno, Viviana Cafiso, et al.. Heteroresistance to glycopeptides in Italian meticillin-resistant (MRSA) isolates. International Journal of Antimicrobial Agents, 2010, 36 (5), pp.415. ⟨10.1016/j.ijantimicag.2010.06.044⟩. ⟨hal-00629959⟩