Foodborne bacteria in slaughterhouses : with focus on cleaning and disinfection

Abstract

Proper cleaning and disinfection (C&D) in slaughterhouses and meat processing premises is a prerequisite for production of safe, high-quality meat. An example of how inadequate C&D can affect human health is provided by the strong increase in number of human cases of campylobacteriosis in Sweden in 2016-2017 due to insufficiently cleaned transport crates for chicken. This thesis evaluated the efficacy of C&D procedures in slaughterhouses and adjacent meat processing premises by testing for pathogenic and hygiene indicator bacteria on equipment, facilities and carcasses. Different sampling methods used for assessing surface cleanliness were compared and slaughterhouses with associated meat processing premises in Sweden were interviewed regarding their C&D routines and monitoring activities. The results indicated that the C&D procedures used for surfaces in the slaughterhouse premises were sufficient regarding removal/inactivation of pathogenic bacteria. However, only approximately half of the surfaces were assessed as sufficiently cleaned, as the amount of hygiene indicator bacteria was high. Campylobacter jejuni, C. coli and Listeria monocytogenes were detected on food contact surfaces, indicating high risk of contamination of carcasses and meat. The same L. monocytogenes strain was found in a red meat slaughterhouse environment on three occasions 15 weeks apart, while a C. jejuni strain showed potential to spread within a poultry slaughterhouse. Extended-spectrum beta-lactamase (ESBL) Escherichia coli was not detected. New technologies such as 265 nm UV-C LED irradiation on chicken transport crates and ultrasound-steam treatment and chilling of broiler carcasses were shown to give significant bacterial reductions. However, these techniques require a certain time of action that is difficult to combine with high slaughter speed in an industrial setting. Dipslides and ATP-bioluminescence were found to be of varying reliability, but are commonly used by Swedish slaughterhouses with associated meat processing premises.