Coagulase-negative staphylococcal bloodstream infections: Does vancomycin remain appropriate empiric therapy?
OBJECTIVE
It is unknown if vancomycin minimal inhibitory concentrations (MICs) have increased in coagulase-negative staphylococci (CoNS) or whether vancomycin remains appropriate empiric therapy.


METHODS
We performed a retrospective study at a single tertiary care center over 8 years. Adult inpatients with ≥2 positive blood cultures for CoNS within a 48-h period were eligible. Susceptibilities were performed by automated broth based-microdilution. Changes in antimicrobial susceptibility were analyzed using logistic regression. The clinical characteristics and outcomes of patients with bloodstream infections (BSI) were compared by MIC.


RESULTS
Of 308 episodes of possible CoNS bacteremia, the vancomycin MIC was ≤1 μg/mL in 80 (26%) isolates, 2 μg/mL in 223 (72.4%) isolates and 4 μg/mL in 5 (1.6%) isolates. No isolates were resistant. We observed an 11-fold increased chance of having an isolate with a vancomycin MIC ≤1 μg/mL in 2009-2011 compared with 2004-2008 (OR 10.8, 95% CI 6.0-19.5, p < 0.05). In 152 patients with BSI, the median days of bacteremia, hospital mortality and readmissions at 30 days were similar in BSI caused by isolates with high vancomycin MICs (2-4 μg/mL) and low vancomycin MICs (≤1 μg/mL).


CONCLUSIONS
We conclude vancomycin is still appropriate empiric therapy for CoNS BSIs. CoNS vancomycin MICs decreased over the study period despite widespread use of vancomycin.
Section of Infectious Diseases, Department of Medicine, Boston University School of Medicine, 771 Albany Street, Dowling Building 3N, Boston, MA 02118, USA. Electronic address: andreav17@hotmail.com.
Paula
P
Valencia-Rey
Department of Biostatistics, Boston University School of Public Health, 801 Massachusetts Ave, Boston, MA 02118, USA. Electronic address: janicew@bu.edu.
Janice
J
Weinberg
Section of Microbiology, Department of Pathology and Laboratory Medicine, Boston Medical Center, 670 Albany Street, Suite 733, Boston, MA 02118, USA. Electronic address: nancy.miller@bmc.org.
Nancy S
NS
Miller
Section of Infectious Diseases, Department of Medicine, Boston University School of Medicine, 771 Albany Street, Dowling Building 3N, Boston, MA 02118, USA. Electronic address: tamar.barlam@bmc.org.
Tamar F
TF
Barlam
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000494:pharmacology* / Q000627:therapeutic use; D003030:Coagulase / Q000172:deficiency; D005260:Female; D006801:Humans; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D012189:Retrospective Studies; D018805:Sepsis / Q000188:drug therapy / Q000382:microbiology*; D013203:Staphylococcal Infections / Q000188:drug therapy / Q000382:microbiology*; D013210:Staphylococcus / Q000187:drug effects*; D062606:Tertiary Care Centers; D014640:Vancomycin / Q000494:pharmacology* / Q000627:therapeutic use; D055815:Young Adult
D000900:Anti-Bacterial Agents; D003030:Coagulase; D014640:Vancomycin
Antibiotic resistance; Antibiotic use; Bloodstream infections; Coagulase-negative staphylococci; Vancomycin