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  • Author or Editor: Nicola L. Williamson x
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Objective—To determine how rapidly trimethoprimsulfamethoxazole affects serum total thyroxine (T4) and thyroid-stimulating hormone (TSH) concentrations in euthyroid dogs and how quickly hormone concentrations return to reference values following discontinuation of administration.

Design—Prospective study.

Animals—7 healthy euthyroid dogs.

Procedure—Dogs were given trimethoprim-sulfamethoxazole (26.5 to 31.3 mg/kg [12 to 14.2 mg/lb], PO, q 12 h) for a maximum of 6 weeks. A CBC and Schirmer tear test were performed and serum total T4 and TSH concentrations were measured weekly. Administration of trimethoprim-sulfamethoxazole was discontinued if total T4 concentration was less than the lower reference limit and TSH concentration was greater than the upper reference limit or if persistent neutropenia developed.

Results—Six dogs had total T4 concentrations less than the lower reference limit within 3 weeks; T4 concentration was decreased after 1 week in 3 of these 6 dogs. In these 6 dogs, TSH concentration was greater than the upper reference limit within 4 weeks. In 1 dog, T4 and TSH concentrations were not affected, despite administration of trimethoprimsulfamethoxazole for 6 weeks. Neutropenia developed in 4 dogs. In 1 dog, the neutropenia resolved while trimethoprim-sulfamethoxazole was still being administered. In the other 3, neutrophil counts returned to reference values 1 week after drug administration was discontinued.

Conclusions and Clinical Relevance—Results suggest that administration of trimethoprim-sulfamethoxazole at a dosage of 26.5 to 31.3 mg/kg, PO, every 12 hours can substantially alter serum total T4 and TSH concentrations and neutrophil counts in dogs within as short a time as a few weeks. (J Am Vet Med Assoc 2002;221:802–806)

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in Journal of the American Veterinary Medical Association


Objective—To determine the methicillin-resistant profile of staphylococcal isolates from the skin of dogs with pyoderma.

Animals—90 dogs with pyoderma.

Procedure—Staphylococci isolated from dogs with pyoderma were tested for susceptibility to methicillin by use of a standard disk diffusion test with oxacillin disks. The DNA extracted from the isolates was tested for the mecA gene that encodes the penicillinbinding protein 2a (PBP2a) by use of a polymerase chain reaction (PCR) assay. The expression of PBP2a was determined with a commercial latex agglutination assay. Species of staphylococcal isolates were identified by use of morphologic, biochemical, and enzymatic tests.

Results—Most of the isolated staphylococci were methicillin-susceptible, coagulase-positive Staphylococcus intermedius isolates. Whereas only 2 of 57 S intermedius isolates were resistant to methicillin, approximately half of the isolates had the mecA gene and produced PBP2a. Staphylococcus schleiferi was the second most common isolate. Widespread resistance to methicillin was found among S schleiferi isolates. More coagulase-negative S schleiferi isolates were identified with mecA gene-mediated resistance to methicillin, compared with coagulase-positive S schleiferi isolates.

Conclusions and Clinical Relevance—The latex agglutination assay for the detection of PBP2a expression coupled with the PCR assay for the mecA gene may provide new information about emerging antimicrobial resistance among staphylococcal isolates. (Am J Vet Res2004;65:1265–1268)

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in American Journal of Veterinary Research