Screening for Intermediately Vancomycin-Susceptible and Vancomycin-Heteroresistant Staphylococcus aureus by Use of Vancomycin-Supplemented Brain Heart Infusion Agar Biplates: Defining Growth Interpretation Criteria Based on Gold Standard Confirmation.

BHI agars supplemented with vancomycin 4 (BHI-V4) and 3 (BHI-V3) mg/liter have been proposed for screening vancomycin intermediately susceptible Staphylococcus aureus (VISA) and heteroresistant (hVISA) phenotypes, respectively, but growth interpretation criteria have not been established. We reviewed the growth results (CFU) during population analysis profile-area under the curve (PAP-AUC) of consecutive methicillin-resistant Staphylococcus aureus (MRSA) blood isolates, which were saved intermittently between 1996 and 2012. CFU counts on BHI-V4 and BHI-V3 plates were stratified according to PAP-AUC interpretive criteria: <0.

Decreasing prevalence of isolates with vancomycin heteroresistance and vancomycin minimum inhibitory concentrations ≥2 mg/L in methicillin-resistant Staphylococcus aureus over 11 years: potential impact of vancomycin treatment guidelines.

We evaluated vancomycin MIC (V-MIC) and the prevalence of intermediately susceptible (VISA) and heteroresistant (hVISA) isolates trends in methicillin-resistant Staphylococcus aureus bacteremia among 720 adults (≥ 18 years) inpatients over 4 study periods (2002-2003, 2005-2006, 2008-2009, and 2010-2012). V-MIC (Etest) and the prevalence of hVISA and VISA (determined by population analysis profile-area under the curve) were stratified according to the study period. Mean vancomycin MIC was 1.

MALDI-TOF identification of Gram-negative bacteria directly from blood culture bottles containing charcoal: Sepsityper® kits versus centrifugation-filtration method.

Matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry has dramatically altered the way microbiology laboratories identify clinical isolates. Direct blood culture (BC) detection may be hampered, however, by the presence of charcoal in BC bottles currently in clinical use. This study evaluates an in-house process for extraction and MALDI-TOF identification of Gram-negative bacteria directly from BC bottles containing charcoal.

Correlation of methicillin-resistant Staphylococcus aureus vancomycin minimal inhibitory concentration results by Etest and broth microdilution methods with population analysis profile: lack of Etest overestimation of the MIC.

Methicillin-resistant Staphylococcus aureus (MRSA) vancomycin minimum inhibitory concentrations (V-MICs) are sometimes reported to be higher according to Etest versus broth microdilution (BMD). These observations are often interpreted as an Etest overestimation of the actual MIC. We measured V-MIC of 484 MRSA blood isolates using Etest, BMD, and a modified BMD (M-BMD) with incremental dilutions parallel to the Etest scale, correlated the results with population analysis profile-area under the curve (PAP-AUC).