Detection of Mycobacterium tuberculosis and Mycobacterium avium Complexes by Real-Time PCR in Bovine Milk from Brazilian Dairy Farms

Abstract

Foodborne diseases are a public health problem worldwide. The consumption of contaminated raw milk has been recognized as a major cause of transmission of bovine tuberculosis to humans. Other mycobacteria that may be present in raw milk and may cause diseases are those belonging to the Mycobacterium avium complex. In this study, molecular biology tools were applied to investigate raw milk contamination with Mycobacterium spp. in family dairy farms from Rio Grande do Sul, southern Brazil. Furthermore, different variables related to the source of the milk, herd characteristics, and management were evaluated for their effect on milk contamination. Five hundred and two samples were analyzed, of which 354 were from the Northwest region (102 farms with samples from 93 bulk tanks and 261 animals) and 148 from the South region of the state (22 farms with samples from 23 bulk tanks and 125 animals). Among them, 10 (1.99%) and 7 (1.39%) were positive for Mycobacterium tuberculosis (9 confirmed as Mycobacterium bovis) and M. avium complexes, respectively. There was no difference in the frequencies of positive samples between the regions or the sample sources. Of the positive samples, 4 were collected from a bulk tank (1 positive for M. avium and 3 for M. tuberculosis). Moreover, 1 sample was positive concomitantly for M. tuberculosis and M. avium complexes. On risk analysis, no variable was associated with raw milk contamination by M. tuberculosis complex species. However, washing the udders of all animals and drying them with paper towels were weakly classified as risk factors for M. avium contamination. Positive samples were obtained from both animals and bulk tanks, which emphasizes the importance of tuberculosis control programs and provides evidence that milk monitoring can be used as a control practice. Moreover, the findings of this study reinforce the need for awareness of the problems of raw milk consumption among the general population.

Reverse zoonotic tuberculosis transmission from an emerging Uganda I strain between pastoralists and cattle in South-Eastern Nigeria

“…This is because the milk samples were collected from individual animals in an aseptic manner into sterile containers, showing the excretion of this organism from the cattle through milk. This is in line with previous reports of M. tuberculosis isolation in cow milk from several parts of the world [21–23]. As previously reported, humans are the initial source of M. tuberculosis infection for animals [22], with potential for this infection being carried back to humans.…”

False-negative reactions to the comparative intradermal tuberculin test for bovine tuberculosis

“…Thus, such animals are often not slaughtered and further investigation is hampered by the difficulty in obtaining samples from live animals. Although attempts at direct diagnosis from live animal samples have been performed with nasal secretion (De Souza Figueiredo et al 2010) and milk (Zarden et al 2013, Bezerra et al 2015, the results are not very encouraging.…”

Tuberculosis in Southern Brazilian wild boars (Sus scrofa): First epidemiological findings

“…Deoxyribonucleic acid (DNA) was obtained from tissues as previously described (Singh et al., ) and quantified in spectrophotometer (L‐quant, Loccus Biotechnology, Brazil). PCR for swine glyceraldehyde‐3‐phosphate dehydrogenase ( GAPDH ) gene—to confirm the absence of DNA inhibitors—and for M. bovis were performed as previously published (Bezerra et al., ). Negative controls were included in all the reactions.…”

“…PCR for swine glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene-to confirm the absence of DNA inhibitors-and for M. bovis were MACIEL ET AL. | 519 performed as previously published (Bezerra et al, 2015). Negative controls were included in all the reactions.…”