Quantifying the mycobiome and its major constituents on the skin of 20 normal dogs.

OBJECTIVE: To report the density, and constituents, of the mycobiome on the skin surface of normal dogs. ANIMALS: 20 normal dogs were recruited for this study, with informed consent in all cases. METHODS: Flocked swabs were used to sample the skin surface and to sample the skin surface after superficial scraping with a blunted scapula. Both samples were taken within a brass guide with an internal area of 3.5 cm-2. Next-generation DNA sequencing was used to identify and quantify components of the mycobiome. RESULTS: The median density of the mycobiome was 1.1 X 105 cm-2 (IQR, 27,561, 409,572). Cladosporium spp and Vishniacozyma victoriae were found on all 20 dogs. CLINICAL RELEVANCE: Knowledge of the density and the composition of the cutaneous mycobiome will increase our understanding of skin biology and may have relevance to future therapeutic trials.

Quantification of the bacterial flora and its major constituents on the abdominal skin of clinically healthy dogs.

OBJECTIVE: To report the density, and the major constituents, of the bacteria on the skin surface of healthy dogs and to assess if scraping the skin before sampling was necessary. ANIMALS: 20 healthy dogs were recruited for the study, with informed consent in all cases. METHODS: Flocked swabs were used to sample the skin surface and to sample the skin surface after superficial scraping with a blunted spatula. Both samples were taken within a brass guide of 3.5 cm-2 area. Next-generation 16S rRNA sequencing was used to identify and quantify components of the bacterial microbiome. RESULTS: The median density of the bacterial microbiome on the ventral abdomen of 20 healthy dogs was approximately 1.1 X 105 cm-2 (IQR 1.22 X 104, 1.6 X 105 cm-2). Sphingomonas species were isolated on 17 of the 20 dogs and Corynebacterium kroppstedtii from 15. CLINICAL RELEVANCE: This is the first study to report the density of the canine skin microbiome. Superficial scraping of the skin before swabbing does not affect the result of sampling the microbiome in healthy dogs. These results will increase our understanding of the biology of canine skin.

A novel cytological technique for bacterial detection on canine skin.

BACKGROUND: Cytological examination of the skin is an important diagnostic technique in dermatology for disease diagnosis and monitoring of treatment. Impression smear and tape-strip preparation are gold standard cytological techniques. This study introduces a novel cytological method, slurry preparation, in which debris collected from the skin surface is macerated in warm sterile water and dried on the slide. HYPOTHESIS/OBJECTIVES: To compare organism yield between a novel and two standard cytological collection techniques by evaluating bacteria and Malassezia yeast counts. ANIMALS: Thirty client-owned dogs diagnosed with atopic dermatitis and lesions consistent with pyoderma and/or Malassezia dermatitis. MATERIALS AND METHODS: In a prospective, blinded comparison study, dermatological lesions from each dog were sampled using impression smear, tape-strip and slurry preparation methodologies. Ten random reticle fields per lesion, accounting for a total area of 6.25 × 10-3 mm2 (equivalent to ˜5% of a typical ×40 field), were evaluated by light microscopy for each cytological method. Bacterial and Malassezia organisms were measured as counts/sample. The slurry preparation was compared to each of the standard methodologies separately using paired Student's t-tests. RESULTS: The slurry preparation was demonstrated to be more sensitive than gold standard techniques in detecting bacteria, with mean differences of 12.7 and 13.5 additional bacteria per cytological sample, compared to the impression and tape-strip preparations, respectively. The slurry preparation did not differ significantly in detecting Malassezia organisms compared with impression smear preparation. The tape-strip preparation was demonstrated to be more sensitive than the slurry preparation in the detection of Malassezia organisms, finding a mean difference of 0.22 more organisms per sample. CONCLUSION: Slurry preparation presents advantages over the gold standard techniques in the detection of bacteria which can help to manage canine pyoderma more appropriately. Performing a slurry preparation in cases of suspected canine pyoderma could be considered as an alternative to the gold standard techniques.

Adverse effects of rifampicin in dogs and serum alanine aminotransferase monitoring recommendations based on a retrospective study of 344 dogs.

BACKGROUND: Rifampicin has been reported to have potent activity against Staphylococci, including meticillin-resistant Staphylococcus pseudintermedius. There is limited documented information regarding adverse effects and recommendations for serum biochemistry monitoring. HYPOTHESIS/OBJECTIVES: The aims of this retrospective study were as follows: (i) to document the occurrence of adverse events in dogs receiving oral rifampicin; (ii) to determine the relationship between adverse events and the dosage/duration of therapy and concurrent medications; and (iii) to report findings associated with changes on serum alanine aminotransferase (ALT). ANIMALS: Client-owned dogs. METHODS: A retrospective review of 344 medical records was carried out. Serum ALT concentrations and adverse effects were recorded and analysed. Correlations between different time intervals (days 0-9, 10-18, 19-27, 28-36 and >36) and serum ALT elevation were compared. RESULTS: Dogs received 2.9-16 mg/kg/day of rifampicin. Adverse events occurred in 16.27% of dogs (56 of 344) and included vomiting (6.97%), anorexia (6.10%) and lethargy (3.77%). Adverse events were significantly more common in dogs concurrently treated with trimethoprim-sulfamethoxazole (P = 0.018), doxycycline (P = 0.044), levothyroxine sodium (P = 0.044), cephalosporins (P = 0.002) and nonsteroidal anti-inflammatories (P < 0.001). Twenty-five of 94 dogs (26.59%) had serum elevations of ALT. These increases were significantly associated with the duration of therapy during two time periods, 19-27 days (P = 0.04) and >36 days (P = 0.01). CONCLUSIONS AND CLINICAL IMPORTANCE: Significant adverse events were noted in association with concurrent drug administration and with serum ALT elevations. Pretreatment and weekly serum biochemistry monitoring is recommended to identify dogs at risk for hepatotoxicosis.

Proliferative, lymphocytic, infundibular mural folliculitis and dermatitis with prominent follicular apoptosis and parakeratotic casts in four Labrador retrievers: preliminary description and response to therapy.

OBJECTIVES: To describe the clinical, histopathological and immunohistochemical lesions and the response to therapy of a novel skin disease in four dogs, and to compare the lesions with those of other similar conditions. METHODS: Clinical lesions, the histopathological findings in skin biopsy samples, immunohistochemistry for CD3 and cleaved caspase-3 and the response to therapy were evaluated. RESULTS: Clinical lesions included multifocal, coalescing, verrucous, crusted papules and plaques with erythematous borders and comedones or follicular casts. Lesions were in haired skin; they occurred at the edges of paw pads and claw beds in one dog. Histopathological lesions included ortho- and more prominent parakeratotic hyperkeratosis involving follicular infundibular epithelium, with cast formation and a papillary epidermal surface. Lymphocytic exocytosis affected all strata of follicular infundibular epithelium and epidermis. Variable numbers of acidophilic shrunken keratinocytes, often bordered by lymphocytes (satellitosis), occupied the more superficial strata of the follicular infundibular epithelium and epidermis. Immunohistochemistry revealed numerous CD3+ T lymphocytes and fewer cleaved caspase-3-positive apoptotic keratinocytes in the infundibular hair follicle epithelium and epidermis, with numerous CD3+ T lymphocytes and cleaved caspase-3-positive cells in the dermis. Two dogs responded completely to therapy with ciclosporin and remained lesion free off therapy; one dog responded to therapy with prednisone, azathioprine and ciclosporin, but relapsed; and one dog was not treated. CONCLUSIONS AND CLINICAL IMPORTANCE: The cause of the lesions is unknown; the presence of intraepithelial CD3+ lymphocytes and cleaved caspase-3-positive apoptotic keratinocytes and the positive response to immunosuppressive therapy suggest an immune response directed towards unidentified antigens expressed on the surface of keratinocytes.

Canine pododermatitis.

This review article is meant to help the general veterinarian differentiate between 12 of the most common skin diseases that cause lesions on the canine paw. Most of these either look the same or have important features that are frequently missed. Each of these conditions will be described and the key features to note will be listed. These key features may be historical or signalment information or they may be diagnostic tests that are critical in making clear diagnostic separations between these diseases.

Pathogenesis of canine interdigital palmar and plantar comedones and follicular cysts, and their response to laser surgery.

This study documents the presence of comedones and follicular cysts of palmar and plantar interdigital skin as an underlying cause of recurrent dermatitis, and describes the use of a carbon dioxide laser to surgically remove lesions. The 28 dogs included in the study had: (i) recurrent lameness, pain, and nodules, or draining sinuses in the dorsal interdigital skin, (ii) failed to respond to antibiotic therapy, and (iii) were negative for Demodex mites and dermatophytes. All 28 had laser surgery; nine dogs had two surgical procedures and two dogs had three surgical procedures for lesion recurrence. Fifteen dogs had skin samples collected for histopathology. Clinical features in ventral interdigital skin included alopecia, callus-like thickening, and comedones. Histological features included hyperkeratosis, acanthosis, comedones and follicular cysts, furunculosis, draining sinuses, and scarring. Surface trauma to the ventral interdigital skin appeared to contribute to lesion development. Laser surgery allowed removal of multiple layers of cysts and adjacent hair follicles and the tracking and removal of sinuses. One dog was euthanized for orthopaedic lameness 1 month after laser surgery, but post-surgical follow-up (1.0-8.0 years - mean 3 years) from the remaining 27 dogs revealed that laser therapy of affected skin and adjacent hair follicles resulted in resolution of interdigital lesions in 25. Two dogs continued to develop interdigital cysts.