Keita Iyori

Identification of a novel Staphylococcus pseudintermedius exfoliative toxin gene and its prevalence in isolates from canines with pyoderma and healthy dogs.

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.

Staphylococcus pseudintermedius exfoliative toxin EXI selectively digests canine desmoglein 1 and causes subcorneal clefts in canine epidermis.

Staphylococcal exfoliative toxins are known to digest desmoglein (Dsg) 1, a desmosomal cell-cell adhesion molecule, thus causing intraepidermal splitting in human bullous impetigo, staphylococcal scalded skin syndrome and swine exudative epidermitis. Recently, a novel exfoliative toxin gene (exi), whose sequence shares significant homology with previously identified exfoliative toxins, was isolated from Staphylococcus pseudintermedius. Little is known about the pathogenic involvement of this toxin in canine pustular diseases such as impetigo. The aim of this study was to determine whether EXI, the product of the exi gene, digests canine Dsg1 and causes intraepidermal splitting in canine skin. An exi gene was isolated from chromosomal DNA of an S. pseudintermedius strain obtained from a pustule of a dog with impetigo, and was used to produce a recombinant EXI by Escherichia coli expression. When purified recombinant EXI was injected intradermally into normal dogs, it caused the development of vesicles or erosions with superficial epidermal splitting. In addition, the EXI abolished immunofluorescence for Dsg1, but not for Dsg3, at the injection sites. Moreover, the EXI directly degraded baculovirus-secreted recombinant extracellular domains of canine Dsg1, but not that of canine Dsg3, in vitro. The EXI also degraded mouse Dsg1α and swine Dsg1, but not human Dsg1, mouse Dsg1β and Dsg1γ. Conversely, recombinant SIET, previously designated as S. intermedius exfoliative toxin, did not cause intraepidermal splitting or degradation of any Dsgs. These findings indicate that EXI has a proteolytic activity that digests canine Dsg1, and this characteristic might be involved in the pathogenesis of intraepidermal splitting in canine impetigo.

Usefulness of cefovecin disk-diffusion test for predicting mecA gene-containing strains of Staphylococcus pseudintermedius and clinical efficacy of cefovecin in dogs with superficial pyoderma

BACKGROUND Cefovecin has been widely used to treat skin infections in dogs. The relationship of the cefovecin disk-diffusion test results to the presence of the mecA gene and the clinical efficacy of cefovecin have not been fully evaluated. HYPOTHESIS/OBJECTIVES To determine the usefulness of an in vitro cefovecin disk-diffusion test in predicting the presence of the mecA gene in Staphylococcus pseudintermedius, as well as the in vivo efficacy of cefovecin therapy in dogs with superficial pyoderma. METHODS Twenty-six S. pseudintermedius strains isolated from 22 dogs with pyoderma were used. In vitro disk-diffusion test results of cefovecin were compared with agar-dilution test results, the presence of the mecA gene, and the improvement in clinical scores of dogs with superficial pyoderma at 14 days post treatment. RESULTS There was a significant linear correlation (r = -0.83) between the diameter of the obvious zone of inhibition by disk diffusion and the minimal inhibitory concentration for cefovecin (P < 0.0001). Receiver operating characteristic analysis revealed that zone diameters between 25 and 27 mm exhibited better sensitivity (92.9%) and specificity (100.0%) for detection of strains carrying the mecA gene. The mean improvement in clinical scores in dogs carrying cefovecin-resistant strains was significantly lower than in dogs carrying cefovecin-susceptible strains (P < 0.01). CONCLUSIONS AND CLINICAL IMPORTANCE The cefovecin disk-diffusion test with a cut-off value estimated in this study was valuable for predicting mecA gene carriage in S. pseudintermedius, as well as the in vivo efficacy of cefovecin therapy in dogs with superficial pyoderma caused by S. pseudintermedius.

Generalized Alopecia with Vasculitis-Like Changes in a Dog with Babesiosis

ABSTRACT A locally bred, 12-year-old, intact female Satsuma dog presented with generalized alopecia. Erythema, crusts and desquamation were observed primarily on the truck. Papules and erosions were present in the pinnae, and there were multiple areas of skin necrosis on the right forelimb. The cutaneous lesions had not responded to treatment with systemic antibiotics and prednisolone. The dog also had progressive anemia. Babesia gibsoni was detected in the blood, and the dog was treated with antiprotozoal agents. The skin lesions and anemia improved, but relapsed after the treatment was discontinued. Histopathological examination of skin biopsies revealed findings suggestive of early leukocytoclastic vasculitis or ischemic vasculopathy.

Collagen-enriched serpiginous skin lesion in a cat resembling the linear form of localized scleroderma in humans

Localized scleroderma (LS) is a sclerotic skin disorder rarely reported in the veterinary literature. We herein report the first case of a linear LS-like skin lesion in a cat. A 1-year-old castrated male Himalayan cat was presented with a 1-month history of an alopecic, indurated, serpiginous, branched skin lesion on the dorsal cervical to scapular area. The cat had no history of trauma, although a topical spot-on endectocide had been applied near the lesion. Histopathological examination revealed a focal area of hyperplastic dermal collagen with the absence of pilosebaceous units. The cutaneous lesion remained unchanged during a 2-year follow-up period. Clinical and histopathological similarities of this skin lesion with those of the linear form of LS in humans were considered.

Re-evaluation of the Cefovecin Disk Diffusion Test for Predicting Oxacillin-resistance in Staphylococcus pseudintermedius Isolated from Dogs

The aim of this study was to re-evaluate the breakpoint of the cefovecin (CFV) disk diffusion test for predicting oxacillin (MPIPC)-resistance in Staphylococcus pseudintermedius isolated from dogs with pyoderma or healthy dogs. There was a significant positive correlation between CFV and the MPIPC disk diffusion zone diameters. The receiver operating characteristic curve revealed that the best CFV breakpoint for predicting MPIPC resistance was ≦ 25 mm. The concordance rate of the susceptibility and resistance to CFV and MPIPC in S. pseudintermedius was 96.9%. In summary, the CFV disk diffusion test with the newly estimated breakpoint is valid for the prediction of MPIPC-resistance in S. pseudintermedius.