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

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.