Heat inactivation data for Mycobacterium avium subsp paratuberculosis: implications for interpretation

Aims: We discuss several factors that are critical for heat inactivation ex periments and which should be taken into account for future research. Methods and Results: On the basis of examples from the literature we discus s critical factors influencing the calculated heat inactivation of Mycobact erium avium subsp. paratuberculosis (MAP). Furthermore, using a modelling a pproach, we show that tailing of the inactivation curve of MAP is caused by the presence of cell clumps and not by a more heat-resistant cell fraction . Conclusions: The experimental conditions of the MAP heat inactivation studi es of different research groups vary significantly and lead to considerable differences in results and conclusions. Therefore, a more consensual appro ach should be employed in future studies. In addition, our model on clumpin g of MAP can be used to predict the decimal reduction of MAP during heat tr eatment and to study the effect of clumping on other lethal effects. Significance and Impact of the Study: We discuss several factors that shoul d be carefully considered in heat resistance experiments. This is essential for a thorough interpretation of results from experiments and should be gi ven proper attention in future experiments and publications on this topic.