Tracking of Mycobacterium Avium Paratuberculosis Load in Milk Production Chain: A Real-Time qPCR And Culture Assay

Abstract

Mycobacterium avium subsp. paratuberculosis (Map) is the causative agent of Johne's disease in ruminants and may contribute to Crohn's disease in humans. This study was conducted to track the changes of Map load throughout the milk production chain to decipher potential sources of contamination. For this purpose, individual cow milk, farm-bulk-milk and bulk milk of collection center were analyzed using F57-quantitative real-time PCR (F57-qPCR) and culture examination. According to the results, the occurrence and the mean value of Map load was increased significantly (P<0.01) from the quarter milk toward bulk-tank milk. Although a positive correlation was found between Map load and number of hygiene indicator bacteria in bulk-raw milks, no correlation was observed between somatic cells count and presence of Map. It was concluded that fecal contamination during hand-milking and/or through the farm environmental plays a major role in increasing Map load in bulk milks. Practical ApplicationsHaving an idea of Map load at each step of milk production and processing chains could be used by food safety organizations to establish regulations for the control of contamination sources. According to the results, Map load was increased from quarter milk en route to the subsequent steps of milk production chain. It was revealed that apart from the primary contamination, a major portion of bulk milk contamination with Map could originate from the farm environment as in nonhygienic practices during teat preparation and hand-milking. Due to the positive correlation of Map contamination and hygiene indicator bacteria, it seems that in endemic areas, high loads of coliforms and enterococci in bulk milks could be deemed as an indication of Map contamination.