Inactivation of Mycobacterium bovis ssp. caprae in high-temperature, short-term pasteurized pilot-plant milk

Abstract

Experiments to determine the efficacy of high temperature, short time (HTST) pasteurization of milk in terms of inactivation of pathogenic microorganisms were mainly performed between 1930 and 1960. Among the target organisms were Mycobacterium bovis and Mycobacterium tuberculosis. As a result, the Codex Alimentarius prescribes that HTST treatment of milk should lead to a significant reduction of pathogenic microorganisms during milk pasteurization. Due to the development of improved methods for the detection of survivors and of more advanced heating technology, verification of this requirement seemed to be necessary. To address recent outbreaks of tuberculosis in cattle caused by M. bovis ssp. caprae (M. caprae) in the southern regions of Germany, this organism was tested and compared with M. bovis ssp. bovis (M. bovis). Experiments were performed in a pilot plant for HTST pasteurization of milk with 3 strains of M. caprae and 1 strain of M. bovis. In preliminary trials at a fixed holding time of 25 s, the temperature at which significant inactivation occurred was 62.5°C for all strains. To determine D-values (decimal reduction times) for the inactivation kinetics, the strains were tested at 65, 62.5, and 60°C at holding times of 16.5, 25, and 35 s. At 65°C, the D-values of all strains ranged from 6.8 to 7.8 s, and at 62.5°C, D-values ranged from 14.5 to 18.1 s. Low inactivation was observed at 60°C. When the low slope of the inactivation curve allowed calculation of a D-value, these ranged from 40.8 to 129.9 s. In terms of log10 reductions, the highest values for all strains were 4.1 to 4.9 log at 65°C, with a holding time of 35 s. The tested strains of M. caprae and M. bovis showed similar low resistance to heat. Standard HTST treatment should result in a high reduction of these organisms and thus the requirements of the Codex Alimentarius for inactivation of pathogens by this process are far exceeded.

Bactericidal effects of high intensity focused ultrasound on Bacillus Calmette–Guerin in vivo and in vitro

“…However, when we heated BCG cells to 55 or 70 C for 45 s, the BCG inactivation rate was significantly higher than that when cells were heated to 25 C (Figure 8(C,D)). Our results were consistent with a previous studies about the thermal inactivation of pathogenic microorganisms such as M. bovis, M.tuberculosis and M. paratuberculosis during milk pasteurization [22,36]. These studies describe that a high-temperature, short-time (HTST) treatment of milk led to a significant reduction of the target organisms.…”

Inactivation Kinetics of Coxiella burnetii During High-Temperature Short-Time Pasteurization of Milk

“…Comparison of the generated data with those in the study of Hammer et al (2015) indicates a higher inactivation of M. bovis and Mycobacterium caprae (>18 log 10 -steps) during HTST treatment of milk than for C. burnetii (>10 log 10steps). This comparatively higher heat resistance is in agreement with the demand, that inactivation of C. burnetii should be the internationally accepted performance criterion for milk pasteurization (Codex Alimentarius, 2009).…”

“…This partly exceeds the requirements of the Codex Alimentarius. Considering the current pasteurization regimes, Hammer et al (2015) demonstrated an 18 log 10 -step reduction of the highly heat-resistant bacterium Mycobacterium bovis (ssp. bovis and caprae ).…”

Tuberculosis patients at the human-animal interface: Potential zooanthroponotic and zoonotic transmission

“…Veterinary inspections are not conducted on home slaughtered carcasses, hence the risk of animal diseases entering the human food chain is higher than in commercially slaughtered livestock. However, heat-treated milk by boiling and thorough cooking of meat products assists with TB control as heat kills the mycobacteria [ 21 ].…”