Comparison of the identification of coagulase-negative staphylococci by matrix-assisted laser desorption ionization time-of-flight mass spectrometry and tuf sequencing

Abstract

The increasing incidence of coagulase-negative staphylococci (CoNS) in hospital-acquired infections underlines the need for an accurate and simple identification of Staphylococcus isolates at the species level. Sequencing of the tuf gene has been shown to be the most accurate for the species identification of CoNS. We determined the species of 62 consecutive clinical and 31 reference CoNS isolates by tuf gene sequencing and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS). Species assignment by MALDI-TOF-MS and tuf sequencing was congruent in all cases. We conclude that MALDI-TOF-MS is accurate for identifying CoNS in routine clinical practice. The study also identified an unexpectedly high number of cases of Staphylococcus capitis infections among 62 consecutive CoNS isolates in 2009 at the University Medical Center Utrecht, the Netherlands.

Fig. 1

Neighbor-joining tree based on the tuf gene sequences of 93 Staphylococcus isolates included in this study. The reference isolates are indicated with the species name and the correlating ATCC number or the number used in the study of Heikens et al. [7]. The clinical isolates are designated CoNS 1 to CoNS 62. The two isolates that did not align with a reference isolate and for which the species was identified using BLAST analysis are indicated as S. lugdunensis – CoNS 44 and S. simulans – CoNS 6. The different colors indicate the different species: pink lineages indicate S. epidermidis isolates, dark blue indicates S. warneri, light blue indicates S. capitis, green indicates S. hominis, yellow indicates S. haemolyticus, and red indicates S. xylosus