Can Mycobacterium avium subsp. paratuberculosis Survive During Pecorino Cheesemaking Process? An Experimental Evaluation Through a Microbiological Challenge Test.

Abstract

Paratuberculosis is an infectious disease mainly affecting domestic ruminants, caused by Mycobacterium avium subsp. paratuberculosis (MAP). Affected animals shed the pathogen through feces, also during the subclinical stages of the disease. Although there is still no conclusive evidence of MAP involvement in human diseases, particularly Crohn's disease and autoimmune disorders, exposure to MAP through the consumption of contaminated dairy products has become a public health concern. Therefore, in this study, the survival of MAP during the production of Pecorino, an Italian cheese made from raw sheep's milk, was investigated by a microbial challenge test. Three batches of raw milk were artificially contaminated with MAP to obtain a concentration of approximately 10CFU/mL, higher than natural conditions. The Pecorino cheesemaking process can reduce the initial MAP concentration by about 1 logafter 60 or 90 days of ripening. The process may act as a hurdle factor against the pathogen, thereby contributing to product safety. Nonetheless, no scientific evidence is currently available regarding MAP contamination levels in raw bulk-tank milk from flocks affected by paratuberculosis, nor quantification of contamination risk relative to flock prevalence. Consequently, as a precautionary measure, milk pasteurization at 72°C for 25 s is recommended to produce Pecorino in flocks with clinical cases of paratuberculosis, regardless of the estimated seroprevalence. PRACTICAL APPLICATIONS: This study provides relevant insights for artisanal producers of Pecorino and similar cheeses, giving evidence of MAP inactivation during the cheesemaking process. These findings support product safety assessment and the competent authority for managing potential public health risks.