Occurrence of Mycobacterium bovis and other mycobacteria in milk samples from cattle in individual and collective bulk tanks of farms from the Central-Western region of São Paulo State

Abstract

The traditional consumption of dairy products, especially cheeses, handmade from milk without heat treatment is a serious health risk. It is estimated that over 90% of all cases of diseases related to consumption of dairy products are of bacterial origin, which are already recognized at least 21 different infections. Mycobacterial infections are among the most debilitating illness that affect humans and animals, being chronic and progressive. These include the tuberculosis, which is among the major zoonoses transmitted through cow's milk. Currently, tuberculosis is considered a re-emerging disease, as confirmed human cases have been increasing significantly since the 1980s. Historically, M. bovis has been associated with extrapulmonary tuberculosis, with greater frequency in children, mainly due to the ingestion of unpasteurized or not subjected to other types of heat treatment milk. In general, in countries where tuberculosis is still prevalent and milk pasteurization is not practiced, it is estimated that 10-15% of human TB cases are caused by M. bovis. The instability of the milk market in Brazil force small farmers to seek alternatives to trade in their production, which includes the sale without sanitary inspection of raw milk to people who prefer this type of milk. So far there are no validated laboratory methods that allow the certification of dairy products without heat treatment as "free of viable mycobacteria". The Ministry of Agriculture (MAPA) implemented the Normative Instruction No. 51 (IN51) in 2002, which among other things, regulates the storage, collection and transportation of refrigerated raw milk. Indeed, the national scientific research involving pathogens milk has a new investigative trend about collecting the samples: the use of collective milk, from one or more herds. Specific studies in other countries have addressed the determination of mycobacteria in samples of milk. However, mycobacterial culture rarely was developed in parallel of molecular tests. In addition, the research generally work only with individual sampling, and not from the bulk tank. This study aims to determine the occurrence of mycobacteria in samples of cattle milk from individual and collective bulk tanks from the central-western region of São Paulo state. Therefore, there will be the cultivation of these samples in both Lowestein-Jensen and Stonebrink media and the Polymerase Chain Reaction by Restriction Enzyme Analysis either directly from milk samples as from isolated colonies that are characterized as acid-fast bacilli. (AU)