Molecular epidemiology of human cases of tuberculosis by Mycobacterium bovis in Mexico

Abstract

The purpose of this study was to evaluate the role of Mycobacterium bovis in human cases of tuberculosis (TB) in an endemic area of the disease in cattle. Sputum, urine and other tissue samples were obtained from: (1) TB-symptomatic patients, (2) dairy farm workers and (3) abattoir workers. Samples of macroscopic lesions suspicious of TB were also obtained from cattle at slaughter in the same geographic area. A total of 562 human samples were collected: 255 from symptomatic patients, 218 from farm workers and 93 from abattoir workers. Samples were analysed by the bacillus acido-alcohol resitant (BAAR) and polymerase chain reaction (PCR) tests and cultured in Stonebrink and Löwenstein-Jensen. Spoligotyping was performed in all isolates obtained by culture and the DNA obtained by PCR. From the total number of human cases, 34 (6%) showed M. bovis spoligotype; eight spoligotypes from cattle showed an identical pattern to three spoligotypes from humans; a different set of spoligotypes from cattle (n = 8) had only one spacer difference to a set of spoligotypes from humans (n = 2). These results provide further evidence that infected cattle represent a risk to public health and support previous reports about the role of M. bovis in Mexican patients. There is no doubt that genotyping M. bovis isolates collected from cattle may have a substantial impact on our understanding of the epidemiology of TB.