Thesis Cork Institute of Technology, 2019.

Includes bibliographical references.

The objective of this study was to investigate the routes of L.monocytogenes contamination in the mushroom industry and propose control actions. A first survey showed that the raw materials contribute to the introduction of L. monocytogenes into the mushroom growing units. Characterisation, by polymerase chain reaction(PCR) and pulse field gel electrophoresis (PFGE), of the isolates obtained from the survey indicated persistent strains, cross contamination between mushroom producers (probably through shared services) similaries with clinical isolates, and the similarity with global clones of L. monocytogenes in several countries. Subsequently, the current hygiene practices in use in the mushroom industry during the production of compost (pasteurisation), casing (physical barriers) and mushrooms (cookout between mushroom crops) were studied. The results showed re-contamination of the compost after pasteurisation, re-contamination in the casing production facility and ineffectiveness of cookout in the inactivation of L.monocytogenes on the floors of growing facilities. Implementation of the hygiene practices have been proposed, but also novel biotechnologies have been studied for future applications. The amidase domain of the listeriophage vB_LmoS_293 endolysin (293-amidase) was cloned and purified. The 293-amidase showed lytic activity against L. monocytogenes autoclaved cells and biofilm inhibition. The 293-amidase protein was also displayed on polyhydroxyalkanoate (PHA) bionanoparticles (BNPs) and preliminary tests showed antilisterial activity. The application of 293-amidase or BNPs in a pilot scale mushroom growing unit showed no efficacy of pre-harvest treatments in the casing or on the floor against L. monocytogenes - (author's abstract)