Evaluation of VITEK-2 System for Antibiotic Susceptibility Test of Streptococcus pneumoniae / 대한임상병리학회지

ABSTRACT

BACKGROUND: The rapid emergence of multi-drug resistant pneumococcal strains has heightened the importance of reliable and convenient susceptibility testing methods. The newly-developed VITEK-2 (bioMerieux, Inc., Hazelwood, MO, USA) System includes the capability of performing rapid susceptibility testing of Streptococcus pneumoniae using specially configured cards. The objective of this study is to evaluate the performance of the VITEK-2 System for susceptibility testing of S. pneumoniae. METHODS: One hundred clinical strains of S. pneumoniae (18 penicillin susceptible strains, 32 intermediate strains, and 50 resistant strains) were tested, which had been isolated in Samsung Medical Center. Minimum inhibitory concentrations (MICs) for penicillin, cefotaxime, erythromycin, ofloxacin, chloramphenicol, tetracyclin, and vancomycin were determined by broth dilution method and VITEK-2 System using AST-P506 cards. The results obtained by VITEK-2 System were compared to those obtained by broth dilution method. RESULTS: Overall agreement of MICs determined by two methods was 93.0% within the range of one dilution. The best agreement was achieved with vancomycin (100%), and in descending order, 99% with ofloxacin, 97% with erythromycin, 94% with chloramphenicol, 89% with cefotaxime, 88% with tetracycline, and 85% with penicillin. There were 1.9% of very major error, 2.0% of major error, and 8.6% of minor error. The mean time for generation of susceptibility results was 9.6 hours. CONCLUSIONS: VITEK-2 System provided rapid and reliable determinations of susceptibility category for most antibiotics and would be helpful as a substitution of existing MIC methods.