Evaluation of MALDI-TOF VITEK®MS and VITEK® 2 system for the identification of Staphylococcus saprophyticus

Abstract

Aim: To compare two identification methods for coagulase-negative staphylococci (CoNS) isolated from patients with urinary tract infections, VITEK^® 2 and MALDI-TOF VITEK^®MS, with genotypic identification by internal transcribed spacer PCR (ITS-PCR).

Results: A total of 217 CoNS isolates were studied. Agreement of the VITEK^® 2 system with ITS-PCR was 84.8%, with 98% sensitivity and 100% specificity. Thirty-one of the 33 strains incorrectly identified by VITEK^® 2 belonged to the species Staphylococcus saprophyticus. MALDI-TOF VITEK^®MS showed an excellent correlation with ITS-PCR since it correctly identified all CoNS isolates.

Conclusion: MALDI-TOF VITEK^®MS is more accurate than the automated VITEK^® 2 system in identifying CoNS isolated from urinary tract infections to species level, particularly urinary isolates of S. saprophyticus.

Keywords: CoNS; ITS-PCR; MALDI-TOF VITEK®MS; VITEK® 2; identification methods; urinary tract infection.