In this section we are going to use simple mathematical techniques, associated with thermobacteriology, to investigate the survival of Mycobacterium avium subsp. paratuberculosis during high temperature short time, HTST, pasteurisation. This organism is often abbreviated M. paratuberculosis, M. avium sub. paratuberculosis or MAP. Two simple equations describing the death of microorganisms by thermal processing have been used to construct several calculators that make it fairly easy for students and others to predict MAP levels in milk following thermal processing.

The methodology used could also be used to investigate the effects of pasteurisation on the destruction of salmonella or say Enterobacter sakazakii ( E. sakazakii has recently been reclassified as a number of distinct species within a new Genus, Cronobacter).

Why study MAP? MAP is interesting for several reasons e.g. there is public health concern about this organism since it has been linked to Crohn’s disease and there is also debate regarding whether it is killed by HTST treatments.

At the end of the article there is an assignment that can be undertaken using the calculators.

This exercise with appropriate adaption should be suitable for second and third year undergraduates in microbiology or food science and students undertaking taught Masters Degrees in Microbiology/Food Science/Food Technology. The exercise could also be used as part of an in company staff development programme. Note prior to undertaking this exercise some prior knowledge of the effects of temperature on the death of microorganisms is required. The calculators can also be used to investigate the effects of thermal processing on the survival of pathogens and thermoduric/thermophilic organisms.

PUBLIC HEALTH SIGNIFICANCE OF MAP

Both Crohn’s disease, a human illness of unknown cause and Johne’s disease,a disease of cattle and other ruminants caused by MAP, are chronic, incurable, inflammatory bowel diseases.