Listeria monocytogenes occurrence and characterization in meat-producing plants

Abstract

Aims:The prevalence, level of contamination and epidemiological profile of Listeria monocytogenes were investigated in two meat-producing plants during a 20-month period. Methods and Results: Sampling for L. monocytogenes was carried out in a cattle slaughterhouse (n ¼ 72) and a swine meat-processing plant (n ¼ 68) during a 20-month period. Swabs and food samples were analysed with the most probable number (MPN) technique for L. monocytogenes and the isolated strains were characterized by AscI-restriction analysis pulsed-field gel electrophoresis (REA-PFGE). Contamination of meat and meat products was always at low level (below 50 MPN per gram). The seven L. monocytogenes positive samples isolated in the bovine slaughterhouse yielded strains with the same REA-PFGE profile. However, the seven strains isolated in the swine meat processing plant showed six different profiles. Two of them showed indistinguishable profiles with L. monocytogenes strains collected from other meat processing facilities located in the same area. Significance and Impact of the Study: The genotyping method is a valuable tool to investigate contamination sources. The study of REA-PFGE profiles indicated that environmental contamination was probably responsible for the persistence of over 16 months of one strain of L. monocytogenes in the cattle slaughterhouse. Several meat suppliers could be responsible for the contamination in the pig meat processing facility, and this is confirmed by the finding of some identical strain in other meat processing facilities located in the same area.

Prevalence of Listeria monocytogenes in pork-meat and other processed products from the Colombian swine industry

“…Prevalence data from this research are consistent with several authors who have pointed out that processing plants are not a significant source of L. monocytogenes contamination. (23)(24)(25)(26)(27). …”

Rapid Quantitative Detection of Listeria monocytogenes in Meat Products by Real-Time PCR

“…Meat products are a major source of L. monocytogenes (9,21,22,24,27,29,32). As clinical cases of listeriosis are usually associated with high loads of L. monocytogenes (10, 11) and as it is difficult to eradicate listeriae from the environment of the food processing plants (12), the International Commission on Microbiological Specification for Foods concluded that 100 CFU of L. monocytogenes per g of food at the time of consumption is acceptable for nonrisk consumers (14,19).…”

Occurrence of Listeria monocytogenes in Salami Manufactured in the Marche Region (Central Italy)

“…L. monocytogenes can easily contaminate raw meat during animal slaughtering and meat processing, and it can persist on contaminated surfaces of processing plants for long periods of time. It can also survive or grow in products across wide ranges of pH and a w , even in the presence of nitrite and nitrate, and at refrigeration temperatures [2,13,15]. Before December 2005, according to the Italian food regulations, there was no tolerance allowed for the presence of L. monocytogenes in readyto-eat meat products in Italy, whereas in other European countries, different criteria for tolerable levels of this pathogen had been established on the basis of risk assessment studies [14].…”