Background – Involvement of Merkel cells (MKs) in different cutaneous diseases as well as in the growth, differentiation and homeostasis of the skin has been previously documented. Hypothesis/Objectives – To assess the ultrastructural features of MKs in the dog skin, including morphometrics, highlighting their similarities and differences with those described for other mammals. Conclusions and clinical importance – The present study represents the first complete description of the ultrastructural characteristics of MKs in the dog, enhancing the knowledge of the skin structure in this species and representing a basic background for future physiological and pathological studies of the role of these cells in normal and damaged canine tissues.

Background – Using the US Clinical and Laboratory Standards Institute (CLSI) human tetracycline breakpoints to predict minocycline and doxycycline susceptibility of Staphylococcus pseudintermedius (SP) isolates from dogs is not appropriate because they do not meet pharmacokinetic/pharmacodynamic data using a standard dose. New breakpoints have been approved for doxycycline and proposed for minocycline. Revised breakpoints are four dilutions lower than tetracycline breakpoints, providing a more conservative standard for classification of isolates. Hypothesis/Objectives – The objectives of this study were to measure minimum inhibitory concentrations (MICs) of minocycline and doxycycline of 100 canine meticillin-resistant SP clinical isolates, compare their susceptibilities to minocycline and doxycycline based on current and revised standards, and document their tetracycline resistance genes. Conclusions and clinical importance – Use of the human tetracycline breakpoints misclassified 45 and five of the isolates as susceptible to minocycline and doxycycline, respectively. PCR analysis revealed that 43 and five of the isolates classified as susceptible to minocycline and doxycycline, respectively, possessed the tetracycline resistance gene, tet(M), known to confer resistance to both drugs. These results underscore the importance of utilizing the proposed minocycline and approved doxycycline canine breakpoints in place of human tetracycline breakpoints.

Background -There is a lack of studies comparing topical antiseptics to systemic antibiotics in the treatment of canine superficial pyoderma. Hypothesis/Objectives - To compare the efficacy of topical chlorhexidine with systemic amoxicillin–clavulanic acid for treatment of canine superficial pyoderma. Conclusion and clinical importance - Topical therapy with chlorhexidine digluconate products may be as effective as systemic therapy with amoxicillin–clavulanic acid. This finding supports the current recommendations to use topical antiseptics alone for management of superficial pyoderma.

Background — The management of canine pemphigus foliaceus (PF) often requires long-term immunosuppressive treatment that is often associated with unacceptable adverse effects. High-dose glucocorticoid pulse therapy, an alternative treatment used for pemphigus in people, has been shown to provide rapid improvement in dogs with pemphigus foliaceus and vulgaris. Objectives — To further identify the benefit of pulse therapy for management of canine PF, we compared the outcomes of oral glucocorticoid pulse therapy and traditional therapy during the first 3 months of disease. Conclusions and clinical importance — These results suggest several benefits associated with oral glucocorticoid pulse therapy, such as a higher proportion of dogs achieving CR during the first 3 months, a lower average maximal oral glucocorticoid dosage given between pulses and minimal adverse drug events.management.

Background – There is a general belief that immune system cells are present in larger numbers in the planum nasale and adjacent haired skin in the dog. However, little published information about the normal histological appearance of the skin of this area exists. Hypothesis/Objectives – The aim was to obtain information about the normal histological appearance of canine skin for specific anatomical regions of the planum nasale and the haired skin adjacent to the planum nasale. Conclusions – Inflammatory change noted in diagnostic biopsies from this area from dogs with clinical disease is likely to be of pathological significance. However, pigmentary incontinence appears to be common at this site in clinically normal dogs without significant inflammatory cell infiltration and is therefore not necessarily of pathological significance when seen in isolation in this location.

Background – Alopecia X in dogs is a noninflammatory alopecia that may be caused by a hormonal dysfunction. It may be similar to androgenic alopecia in men that is caused by the effect of dihydrotestosterone (DHT). The 5areductase isoenzymes, 5aR1 and 5aR2, and a recently described 5aR3, are responsible for the conversion of testosterone into DHT. However, which 5a-reductases are present in canine skin has not yet been described. Objectives – The main objective of this study was to determine the pattern of expression of 5a-reductase genes in canine skin. Conclusions and clinical importance – To the best of the authors' knowledge, this is the first study demonstrating the expression of 5a-reductases in canine skin and the expression of 5aR3 in this tissue. These results may help to elucidate the pathogenesis of alopecia X and to determine more appropriate treatments for this disorder.

Background – Up to 0.5% of churra lambs from two genetically related flocks showed congenital skin lesions of variable severity, jeopardizing the life of the lambs in the most severe cases. Hypothesis/Objectives – The primary objective of this study was to classify the type of congenital epithelial disease suffered by these animals, based on the description of the macroscopic skin defects, the histological and ultrastructural changes, and the hereditary nature of the condition. Conclusion and clinical importance – The pathological findings and mode of inheritance in these lambs are similar to an inherited epidermolysis bullosa subtype of humans, which has not been reported previously in veterinary medicine.