Staphylococcus pseudolugdunensis sp. nov., a pyrrolidonyl arylamidase/ornithine decarboxylase-positive bacterium isolated from blood cultures

Twelve coagulase-negative staphylococcal isolates recovered from blood cultures with positive pyrrolidonyl arylamidase and ornithine decarboxylase reactions were identified as Staphylococcus lugdunensis by the clinical microbiology laboratory. However, none of these 12 isolates were recognized by a S. lugdunensis translation elongation factor Tu (tuf) gene-specific probe. Under the API STAPH V4.0 identification system (bioMérieux, Durham, NC), 8 of these 12 isolates could not be identified with low discrimination scores, and 4 were identified as Kocuria varians/rosea with identification probabilities that ranged from 95.5% to 99.6%. All 12 isolates possessed identical partial 16S rRNA gene sequences, and the full 16S rRNA gene sequences of the prototype strain B006 were closely related to a tentatively assigned “Staphylococcus pettenkoferi”. All 12 isolates had identical partial tuf gene sequences corresponding to 666 to 858 nucleotide positions, and the 1188-base pair full tuf sequences of B006 strain were mostly related to 2 Staphylococcus epidermidis isolates with a 93.02% similarity. Two isolates, which were recovered from the same patient over a 16-day interval, were considered to be a pathogen causing an intravenous line-associated infection; the remaining 10 isolates were considered to be skin contaminants. Biochemical tests currently used in the clinical microbiology laboratory to identify S. lugdunensis appear to lack specificity in identifying these isolates. On the basis of the close biochemical reactions with S. lugdunensis and phylogenetic evidence, these isolates are proposed the designation Staphylococcus pseudolugdunensis sp. nov.