Reclassification of phenotypically-identified Staphylococcus intermedius strains

Department of Infection Control Science, Faculty of Medicine, Juntendo University, Tokyo 113-8421, Japan and Department of Veterinary Hygiene, Veterinary School, Nippon Veterinary & Life Science University, 1-7-1 Kyounan, Musashino, Tokyo 180-8602, Japan

^* To whom correspondence should be addressed. Email: kikuti{at}med.juntendo.ac.jp.

	Abstract

To reclassify phenotypically-identified Staphylococcus intermedius which might include true S. intermedius and novel species as Staphylococcus pseudintermedius and Staphylococcus delphini, we analyzed molecular phylogeny and phenotypic characteristics of 117 S. intermedius group (SIG) strains tentatively identified as S. intermedius by rapid ID32 Staph. From phylogenetic analysis of sodA and hsp60 sequences, the SIG strains were divided into 3 clusters, which belonged to S. pseudintermedius LMG 22219^T, S. intermedius ATCC29663^T and S. delphini LMG 22190^T. All the SIG strains from dogs, cats, and humans were identified as S. pseudintermedius. The wild pigeon strains except one were identified as S. intermedius, and strains from all domestic and one wild pigeons, horses and a mink were identified as S. delphini. In addition, phylogenetic analysis of nuc genes revealed that S. delphini strains were divided into 2 clusters, one was the cluster (S. delphini group A) belonged to S. delphini LMG 22190^T, and the other was the cluster (S. delphini group B), which was more related to S. pseudintermedius LMG 22219^T than S. delphini LMG 22190^T. The DNA-DNA hybridization results yielded that S. delphini-group B strains were distinguished from S. delphini group A, S. intermedius and S. pseudintermedius. S. intermedius is distinguishable from S. pseudintermedius or S. delphini by positive-arginine dihydrolase, and acid production from -gentiobiose and D-mannitol. However, phenotypical characteristics to differentiate S. delphini-group A, group B and S. pseudintermedius were not found. In conclusion, SIG strains were reclassified into 4 clusters with 3 established and one probably novel species.