Isolamento e identificação de Mycobacterium spp. em bovinos positivos no teste de tuberculinização.

Abstract

In areas where human and bovine tuberculosis coexist, the differentiation between M. bovis and M. tuberculosis is important for monitoring the spread of M. bovis among cattle and from cattle to humans, so that the objective of this study was to isolate and identify M. bovis from cattle with a positive diagnosis identified using tuberculin test in the State of Paraíba, Northeastern Brazil. It were used 32 bovines positive at the tuberculin test, from which samples of any organ with tuberculosis suggestive lesions were collected, or samples of parotid, sublingual, retropharyngeal, mediastinal or mesenteric lymph nodes were collected when no gross lesions were observed. Milk samples were collected from 16 cows from seven herds. Histopathological exams, mycobacteriological culture, Ziehl Neelsen staining and molecular diagnosis were performed. Twenty-one (65.6%) animals presented tuberculosis suggestive lesions. Macroscopically, it were observed caseous and/or calcified nodular granulomatous lesions, focal and disseminated, of varying size and shape. Microscopically, it were evidenced inflammation of granulomatous type at different stages, with extensive granuloma characterized by central area of coagulation necrosis, homogeneous eosinophilic material, fragmented nuclei, nuclear debris and mineralization foci surrounded by inflammatory infiltrate predominantly macrophages and epithelioid cells encapsulated by abundant fibrous connective tissue associated with several layers of mononuclear cells. Related to distribution of lesions according to body region 77.7% were from thoracic cavity, 12.4% from head and 9.9% from abdominal cavity. Of 55 samples submitted to mycobacterial culture in 31 (56.4%) mycobacteria were isolated, being 13 (41.9%) identified as M. bovis and 18 (58.1%) as Mycobacterium spp. Mycobacteria were isolated from five (31.25%) of the 16 milk samples; three samples were classified as M. bovis, and two as belonging to the Mycobacterium genus. It is concluded that the isolation and identification of M. bovis and Mycobacterium spp. in bovines positive at tuberculin test in the State of Paraiba, Northeastern Brazil suggests that humans are exposed to the risk of infection. This reinforces the need for intensification and optimization of prevention and control measures foreseen in the Bovine Brucellosis and Tuberculosis National Control and Eradication Program (PNCEBT) as encouraging certification of tuberculosis-controlled and free rural properties and control of animal movement and fairs. Particular attention should be given to the importance of sanitary inspection of slaughtered animals in the identification of tuberculosis foci, and it is suggested to carry out mycobacteria isolation and identification surveys in other Northeastern states.