ABSTRACT. To understand species distribution, trends of antimicrobial susceptibility and prevalence of methicillin resistance in canine staphylococci in Japan, 190 coagulase-positive staphylococci (CoPS) were isolated from dogs with pyoderma in 2 Japanese veterinary referral hospitals. Using a multiplex polymerase chain reaction (M-PCR) method, two CoPS species were identified: 170 Staphylococcus pseudintermedius (89.5%) and 20 S. schleiferi subsp. coagulans isolates (10.5%). In these isolates, susceptibility to 7 antimicrobial agents was determined. Overall, the levels of susceptibility to cefalexin (CEX), amoxicillin/clavulanic acid (CVA/AMPC), minocycline (MINO), ofloxacin (OFLX), norfloxacin (NFLX), lincomycin (LCM) and clindamycin (CLDM) in S. pseudintermedius isolates were 38.2, 52.4, 34.7, 31.2, 34.1, 1.2 and 11.2%, respectively. In S. schleiferi subsp. coagulans isolates, 55% demonstrated susceptibility to CEX, 80% to CVA/AMPC, 70% to MINO, 45% to OFLX or NFLX and 30% to CLDM. None of S. schleiferi subsp. coagulans isolates was susceptible to LCM. To determine the prevalence of methicillin-resistant strains, we used a PCR method, which enabled detection of the fragment of mecA gene in 66.5% (113 of 170) in S. pseudintermedius and 30.0% (6 of 20) in S. schleiferi subsp. coagulans isolates. The frequencies of susceptibility to CEX, CVA/AMPC, OFLX, NFLX and CLDM were significantly lower in methicillin-resistant CoPS than in methicillin-susceptible CoPS isolates. These data suggest a high level of methicillin resistance in staphylococci isolated from dogs with pyoderma in Japan.

The clinical efficacy of a surgical scrub containing 2% chlorhexidine acetate (2CA; Nolvasan® Surgical Scrub; Fort Dodge Animal Health, USA) was evaluated for the topical management of canine superficial pyoderma. The first study was a randomized, double-blind, controlled trial. The control was a shampoo containing 4% chlorhexidine gluconate (4CG; Skin Clinic Shampoo; CHD MEDICS, Goyang, Korea). Ten dogs with symmetrical lesions of canine superficial pyoderma were allocated to receive either 2CA or the control shampoo applied to either side of the body twice weekly for 1 week. Both the owners and the investigators subjectively scored skin lesions including pruritus, erythema, crusted papules and scales on a scale of 0-3. The 2CA and 4CG resulted in almost the same degree of improvement of skin lesions, and there were no significant differences between the two groups. The second study was an open trial of 2CA monotherapy in eight dogs with cefalexin-resistant Staphylococcus intermedius group-associated superficial pyoderma. The 2CA monotherapy was applied every 2 days for 2 weeks. Five dogs improved with 2CA monotherapy, one partially improved and two did not. No adverse reactions were seen in either trial. This suggests that a 2CA surgical scrub could be a useful and safe topical adjunct therapy for dogs with superficial pyoderma involving cefalexin-resistant Staphylococcus intermedius group.

Staphylococcal exfoliative toxins are involved in some cutaneous infections in mammals by targeting desmoglein 1 (Dsg1), a desmosomal cell-cell adhesion molecule. Recently, an exfoliative toxin gene (exi) was identified in Staphylococcus pseudintermedius isolated from canine pyoderma. The aim of this study was to identify novel exfoliative toxin genes in S. pseudintermedius. Here, we describe a novel orf in the genome of S. pseudintermedius isolated from canine impetigo, whose deduced amino acid sequence was homologous to that of the SHETB exfoliative toxin from Staphylococcus hyicus (70.4%). The ORF recombinant protein caused skin exfoliation and abolished cell surface staining of Dsg1 in canine skin. Moreover, the ORF protein degraded the recombinant extracellular domains of canine Dsg1, but not Dsg3, in vitro. PCR analysis revealed that the orf was present in 23.2% (23/99) of S. pseudintermedius isolates from dogs with superficial pyoderma exhibiting various clinical phenotypes, while the occurrence in S. pseudintermedius isolates from healthy dogs was 6.1% (3/49). In summary, this newly found orf in S. pseudintermedius encodes a novel exfoliative toxin, which targets a cell-cell adhesion molecule in canine epidermis and might be involved in a broad spectrum of canine pyoderma.

A 10-year-old castrated male Shih Tzu presented with severe generalized pruritus. Skin scrapings revealed the presence of Sarcoptes scabiei var. canis. A Yorkshire terrier in the same household simultaneously developed pruritus due to scabies. Both dogs were treated with 300 μg/kg ivermectin, at first orally and then subcutaneously at 14 day intervals. However, live mites were still found on day 35, and the skin condition deteriorated in both dogs. These findings suggested that the S. scabiei in these dogs was clinically refractory to ivermectin. The pruritus in both dogs rapidly and completely disappeared following topical fipronil administration. This appears to be the first report of canine scabies refractory to ivermectin treatment.

No abstract