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 1.78 ± 0.39, 1.81 ± 0.47, 1.68 ± 0.26, and 1.54 ± 0.28 mg/L in 2002-2003, 2005-2006, 2008-2009, and 2010-2012, respectively (P < 0.0001). We noted a steadily decreasing prevalence of isolates with V-MIC ≥ 2 mg/L (50.0%, 45.2%, 35.4%, and 18.7%; P < 0.0001) and hVISA (9.7%, 6.6%, 3.0%, and 2.1%; P=0.0003). VISA prevalence remained low (0-2%). These changes coincided with steadily increasing vancomycin trough levels (9.9 ± 7.8, 11.1 ± 8.4, 16.6 ± 7.8, and 19.7 ± 5.9 mg/L in 2002-2003, 2005-2006, 2008-2009, and 2010-2012, respectively; P < 0.0001). These changes imply that adherence to vancomycin treatment guidelines may suppress the development of less susceptible isolates.
Department of Medicine, St John Hospital & Medical Center, Detroit, MI, USA. Electronic address: riad.khatib@stjohn.org.
Riad
R
Khatib
Department of Medicine, St John Hospital & Medical Center, Detroit, MI, USA.
Mamta
M
Sharma
Department of Medicine, St John Hospital & Medical Center, Detroit, MI, USA.
Leonard B
LB
Johnson
Department of Medicine, St John Hospital & Medical Center, Detroit, MI, USA.
Kathleen
K
Riederer
Department of Medicine, St John Hospital & Medical Center, Detroit, MI, USA.
Stephen
S
Shemes
Department of Medicine, St John Hospital & Medical Center, Detroit, MI, USA.
Susan
S
Szpunar
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000494:pharmacology* / Q000627:therapeutic use; D016470:Bacteremia / Q000453:epidemiology / Q000382:microbiology; D004361:Drug Tolerance; D004363:Drug Utilization / Q000592:standards*; D005260:Female; D006801:Humans; D008297:Male; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects*; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D015995:Prevalence; D012189:Retrospective Studies; D013203:Staphylococcal Infections / Q000188:drug therapy / Q000453:epidemiology* / Q000382:microbiology*; D014640:Vancomycin / Q000494:pharmacology* / Q000627:therapeutic use; D055815:Young Adult
D000900:Anti-Bacterial Agents; D014640:Vancomycin
Bacteremia; Heteroresistance; Staphylococcus aureus; Vancomycin