Isolation of Mycobacterium spp. in milk from cows suspected or positive to tuberculosis

English. This study was performed considering the public health hazards related to the elimination of mycobacteria through milk of dairy cows suspected or positive for tuberculosis presenting no clinical alterations. A total of 780 milk samples from 52 animals, positive or suspected for tuberculosis, according to Stormont's test, were analysed to detect Mycobacterium spp. The samples consisted of 300 ml/cow, collected in the first milking of the day, during 15 days. Frozen samples were sent to the laboratory, inoculated in Löwenstein-Jensen with reduced glicerol (0.5%) and Stonebrink media and kept under 37ºC for at least 90 days. The genus of each observed colony was initially confirmed by Ziehl-Neelsen and auramin staining methods. The isolation of Mycobacterium spps was confirmed in 78 (10%) samples collected from 19 (36.54%) animals. According to thin layer chromatography, time and temperature growth characteristics and colonies aspects, the 19 animals eliminated: M. avium (5.26%), M. fortuitum (10.52%), M. bovis (5.26%) and Mycobacterium spp. (78.95%).

Portuguese. Considerando-se o risco à saúde pública representado pela eliminação de micobactérias pelo leite, foram colhidas 780 amostras de 52 fêmeas bovinas leiteiras consideradas suspeitas ou positivas para tuberculose ao teste de Stormont. As amostras foram submetidas à pesquisa de Mycobacterium spp. e consistiam de 300 ml de leite/vaca, colhidos na primeira ordenha do dia, durante 15 dias. As amostras congeladas foram enviadas ao laboratório, processadas pelas técnicas preconizadas por Kantor16, Quinn et al.24 e Corner et al.5, inoculadas em meios de Löwenstein-Jensen com teor reduzido de glicerol (0,5%) e de Stonebrink, e incubadas a 37ºC por um período mínimo de 90 dias. O gênero de cada colônia isolada foi inicialmente confirmado pelos métodos de coloração de Ziehl-Neelsen e da auramina. O isolamento de Mycobacterium spp. foi confirmado em 78 (10%) amostras provenientes de 19 (36.54%) animais. De acordo com a cromatografia em camada delgada, as características de tempo e temperatura de crescimento e os aspectos coloniais, os 19 animais eliminaram: M. avium (5.26%), M. fortuitum (10.52%), M. bovis (5.26%), and Mycobacterium spp. (78.95%).