Miosite necrótica bacteriana difusa causada por Staphylococcus ssp. em um bovino

Abstract

The dermatitis caused by non-filamentous bacteria such as Staphylococcus spp. is usually known as botryomycosis because normally it presents a granulomatous lesion. This condition is the result of the infection and its recommended treatment in veterinary practice includes surgical removal and systemic antibiotic therapy. Microscopically, the staphylococcal infection results in the formation of a reaction named “Splendore-Hoeppli reaction”, characterized by bacterial aggregates and immunological cells encapsulated by an eosinophilic amorphous material. The development of extensive necrosis areas is rare. The aim of this study is to report a case of necrotic myositis in a male dairy Gyr bovine whose wound on the right anterior limb was not treated correctly with antibiotics and evolved to a marked inflammation of the limb. A corticosteroid based on dexamethasone was used to try and reduce the inflammatory response and edema on the limb, this led to the animal’s immunosuppression and contributed to the septicemia that culminated with its death. The necropsy was performed at the Laboratório de Patologia Veterinária of Universidade Federal da Paraíba, to obtain the final diagnosis, along with the clinical signs demonstrated by the animal and its owner’s history. Macroscopic lesions observed on the skin and subcutis were edema and the formation of a fibrinosuppurative process with the presence of a fetid darkened exudate. Microscopically a marked neutrophilic inflammation and fibrin was observed associated with muscle necrosis. It was also noted a marked congestion of the spleen, kidneys, liver, lungs, and adrenal glands, along with pooling of blood in these tissues. Excerpts of muscle were sent to be microbiologically evaluated at the Laboratório de Medicina Preventiva of UFPB where the Staphylococcus spp. bacteria was isolated, cultured and identified, after the catalase, oxidase, and Gram tests. This case report concludes that skin lesions may serve as an entrance to bacteria which multiply on muscle tissue and may cause cellulitis and myositis, which evolve to septicemia when neglected. The misuse of glucocorticoids may contribute to the suppression of the animal’s immunological response.