Efficacy of MALDI-TOF mass spectrometry as well as genotypic andphenotypic methods in identification of staphylococci other thanStaphylococcus aureus isolated from intramammary infectionsin dairy cows in Poland

摘要

We compared the effectiveness of various methods for the identification of spp. other than S. isolated from intramammary infections of cows on 3 dairy farms in Lower Silesia,Poland. A total of 131 isolates belonging to 18 species were identified by sequence analysis of the 16S rRNA and genes, as well using a commercial identificationsystem (ID 32 STAPH; bioMérieux) and matrix-assisted laser desorption/ionizationtime-of-flight mass spectrometry (MALDI-TOF MS; Bruker Daltonics). Sequencing ofthe 16S rRNA gene was found to have low discriminatory value because only 43% ofisolates were recognized unequivocally. Much better results were obtained withthe gene (all isolates were correctly identified at thespecies level). However, some of these isolates achieved a low similarity level(<97%) and required a confirmatory test (sequencing of the gene). The performance of ID 32 STAPH was poor.Regardless of the probability level used (80% or 90%), the commercial systemobtained identification rates <40%. Using MALDI-TOF MS and the commercialBruker database, 67% of isolates were identified correctly with scores ≥2.0(acceptable species-level identification) but this number increased to 97% afterthe database was expanded. The definitive identification of spp. other than causing intramammary infections in cattle often requires a combination ofdifferent procedures, and the existing databases should be updated.