Evaluation of residual antibacterial effects on canine skin surface and hair following treatment with five commercial mousse products against Staphylococcus pseudintermedius.

BACKGROUND: Antibacterial effect studies of commercial antiseptics typically have evaluated hair and not the skin. OBJECTIVES: To evaluate the antibacterial effects of mousse products on both canine skin and hair. ANIMALS: Fifteen short-haired and eight long-haired dogs without skin disease. MATERIALS AND METHODS: Five mousses were applied once: (1) 2% chlorhexidine and 2% miconazole; (2) 0.05% phytosphingosine; (3) 2% salicylic acid and 10% ethyl lactate; (4) 3% chlorhexidine and 0.5% climbazole; and (5) 2% chlorhexidine and 1% ketoconazole. Skin swabs and hair were collected from application sites before treatment, and at 1 h and at Day (D)2, D4, D8, D10 and D14 post-treatment. Skin swabs and hair were placed on Mueller-Hinton plates inoculated with Staphylococcus pseudintermedius inoculum suspension. Inhibition zones were measured after incubation. RESULTS: Inhibition was not noted with mousses 2 and 3. In mousse 5, inhibition zone sizes produced by swabs from long- and short-haired dogs were not significantly different (p = 0.105), and all swabs and hair produced inhibition until D14, regardless of hair length. By contrast, in mousse 1, inhibition zones produced by swabs from long-haired dogs were smaller than those from short-haired dogs (p < 0.001), and swabs from long-haired dogs produced a shorter duration of bacterial inhibition than hair. CONCLUSIONS AND CLINICAL RELEVANCE: The antibacterial effects of mousse 5 were not affected by hair length. Hair may be acceptable for evaluating effects on the skin in short-haired dogs. However, long hair may interfere with product distribution and duration of bacterial inhibition. Therefore, the evaluation of hair alone may overestimate clinically relevant antibacterial effects.

Cutaneous Mycobacterium goodii infection in an immunocompetent cat in Louisiana: clinical presentation, molecular identification, antimicrobial susceptibility and management.

Case summary: A 9-year-old spayed female domestic shorthair cat was presented to a referral hospital for management of recurring non-healing ulcerations and a subcutaneous mass on the ventral abdomen. Prior treatment included antibiotics (cefovecin followed by clindamycin), wound cleaning and surgical debulking, but the ulcerations and mass recurred 1 month after surgical removal. At this point, the cat was started on doxycycline and pradofloxacin and referred for further work-up. The culture of skin biopsy specimens obtained at the time of referral revealed a population of bacterial colonies with two distinctly different phenotypes. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and 16S rRNA gene sequencing identified both colonies as Mycobacterium goodii. A diagnosis of a cutaneous infection of rapidly growing mycobacteria was made, and treatment with oral pradofloxacin and doxycycline was initiated. The ulcerations resolved within 4 months, and the subcutaneous mass gradually decreased in size until it was no longer palpable, even 4 months after the cessation of antibiotics. Relevance and novel information: This is the second reported feline cutaneous M goodii infection in North America. The organism was not visualized on histopathology but was successfully cultured from tissue obtained by skin punch biopsy. A phenotypic switching phenomenon affecting the susceptibility results was suspected, possibly explaining the presence of phenotypically different but genetically identical strains. This case highlights the importance of submitting aseptically obtained tissue, fluid or fine-needle aspirates for culture and species identification, as well as histopathology, when infection with higher bacteria, such as rapidly growing mycobacteria, is suspected.

Pathology in Practice.

In collaboration with the American College of Veterinary Pathologists.