Relevance of vancomycin-intermediate susceptibility and heteroresistance in methicillin-resistant Staphylococcus aureus bacteraemia.

Objectives: To assess the relevance of vancomycin-intermediate susceptibility (VISA) and heteroresistance (hVISA) in methicillin-resistant Staphylococcus aureus (MRSA) bacteraemia.

Methods: We determined vancomycin MICs for 371 saved MRSA blood isolates (2002-03; 2005-06) by Etest and broth microdilution (BMD), screened for hVISA (Etest methods), determined the population analysis profile (PAP)/AUC for isolates with suspected reduced susceptibility (MICs >2 mg/L and/or hVISA-screen-positive versus Mu3 (hVISA control), and stratified patient characteristics and outcome according to susceptibility phenotype: VISA (PAP/AUC >1.3), hVISA (PAP/AUC 0.

Vancomycin MIC plus heteroresistance and outcome of methicillin-resistant Staphylococcus aureus bacteremia: trends over 11 years.

Vancomycin MICs (V-MIC) and the frequency of heteroresistant vancomycin-intermediate Staphylococcus aureus (hVISA) isolates are increasing among methicillin (meticillin)-resistant Staphylococcus aureus (MRSA) isolates, but their relevance remains uncertain. We compared the V-MIC (Etest) and the frequency of hVISA (Etest macromethod) for all MRSA blood isolates saved over an 11-year span and correlated the results with the clinical outcome. We tested 489 isolates: 61, 55, 187, and 186 isolates recovered in 1996-1997, 2000, 2002-2003, and 2005-2006, respectively.