Method-specific performance of vancomycin MIC susceptibility tests in predicting mortality of patients with methicillin-resistant Staphylococcus aureus bacteraemia

Shey Ying Chen, Chun Hsing Liao, Jiun Ling Wang, Wen Chu Chiang, Mei Shu Lai, Wei Chu Chie, Shan Chwen Chang, Po Ren Hsueh

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

Objectives: Emerging evidence shows that methicillin-resistant Staphylococcus aureus (MRSA) infections caused by isolates with higher vancomycin MICs within the susceptibility range are associated with adverse outcomes. No study, however, has examined different susceptibility tests in predicting treatment outcomes of MRSA infections. Methods: This retrospective cohort study included 393 patients with MRSA bacteraemia. Vancomycin MICs for all MRSA isolates were determined simultaneously by agar dilution and the Etest, and using the MicroScan, VITEK-2 and Phoenix automated systems, and categorized into low- and high-MIC isolates at a breakpoint of>2 mg/L. The essential and categorical agreement between testing methods was compared. The method-specific ability to predict in-hospital mortalitywas examined by multivariate logistic regression analysis controlling for other potential confounders using clinical data from 310 vancomycin-treated MRSA bacteraemia patients. Results: The agar dilution, Etest, MicroScan, VITEK-2 and Phoenix methods assessed 14.2% (56/393), 9.7% (38/393), 28.8% (113/393), 22.6% (89/393) and 3.1% (12/393) of MRSA isolates as having high (≥2 mg/L) vancomycin MICs. The essential and categorical agreement between testing methods ranged from 98.5% to 100% and from73.8% to 91.9%, respectively. Highvancomycin MICs for isolates determined using agar dilution and the Etest independently predicted mortality when controlling for confounding factors [adjusted OR, 2.321; 95% CI, 1.160-4.641; and adjusted OR, 3.121; 95% CI, 1.293-7.536, respectively]. High vancomycin MICs determined using all three automated systems failed to predict mortality. Conclusions:Vancomycin MICs generated bythe agar dilutionandEtest methods, but not theautomated systems, independently predicted mortality among vancomycin-treated MRSA bacteraemia patients. Clinicians should incorporate this information with clinical assessment for decisions on appropriate anti-MRSA treatment.

Original languageEnglish
Article numberdkt340
Pages (from-to)211-218
Number of pages8
JournalJournal of Antimicrobial Chemotherapy
Volume69
Issue number1
DOIs
Publication statusPublished - 2014 Jan 1

All Science Journal Classification (ASJC) codes

  • Pharmacology
  • Microbiology (medical)
  • Infectious Diseases
  • Pharmacology (medical)

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