Isolation and characterization of staphylococci from external auditory meatus of dogs with or without otitis externa with special reference to Staphylococcus schleiferi subsp. coagulans isolates

Staphylococci were isolated from the external auditory meatus in 14 (48.3%) of 29 dogs affected with otitis externa (OE dogs) and 28 (68.3%) of 41 dogs without OE (non-OE dogs). Twenty-two OE isolates were identified as belonging to 12 species, and 42 non-OE isolates were identified as belonging to 13 species. The predominant species found in both OE and non-OE isolates were S. intermedius, and S. epidermidis. Thirty-eight (59.4%) of 64 isolates were resistant to one or more of the 17 antimicrobial agents tested. Resistance to PCG and ABPC was most frequent. S. schleiferi subsp. coagulans, a recent etiologic agent of canine OE, was isolated from OE and non-OE dogs. All of the 5 S. schleiferi subsp. coagulans isolates showed typical characteristics. No clear difference in the extracellular enzyme or toxin profiles, nor in the PFGE patterns, was demonstrated between the OE and non-OE isolates of S. schleiferi subsp. coagulans. A new PCR primer set specific for 16S rDNA was designed to identify strains of S. schleiferi subsp. coagulans. The amplified fragment was detected in all of the 5 isolates as well as the type strain GA 211 (=JCM 7470) and a reference strain GA 11, but was not detected in any strains of the related species, S. aureus, S. intermedius and S. hyicus. The PCR may allow a simple, rapid and precise identification of S. schleiferi subsp. coagulans, in addition to the standard tube test for free coagulase.