Species Distribution of Staphylococci in the Nares and Skin of Horses

During a 2-year period from 1996 to 1997, a total of 1,089 staphylococci were isolated from the nares and skin of 99 healthy horses reared at 15 farms in the Hidaka District, Hokkaido, Japan. Identification of the 1,089 isolates resulted in the following species distribution: Staphylococcus xylosus, 883 isolates (81.1%); S. sciuri (subspecies not identified), 133 (12.2%); S. cohnii subsp. cohnii, 16; S. hominis (subspecies not identified), 11; S. haemolyticus, 10; S. gallinarum, 7; S. lentus, 7; S. simulans, 3; S. cohnii subsp. urealyticum, 2; S. epidermidis, 1; S. intermedius, 1; S. saprophyticus (subspecies not identified), 1; S. lugdunensis, 1; S. schleiferi subsp. schleiferi, 1; S. capitis (subspecies not identified), 1; S. caprae, 1; unidentifiable, 10. No difference was found between the nares and the skin regarding staphylococcal species distribution. This suggests that for the most part S. xylosus and S. sciuri comprise the staphylococcal flora in horses. For identification, 16S-23S rDNA intergenic spacer PCR analysis was used as well as the Api Staph system. It was confirmed that this method is a useful tool for identification when there are many isolates to deal with. In this study, we designed two primer sets for PCR specific for 16S rDNA of S. sciuri or S. lentus in order to distinguish the 2 species, because it is difficult to identify them definitively in terms of phenotypic characteristics alone. These primer sets were useful in distinguishing these species.