Elsevier

Meat Science

Volume 83, Issue 2, October 2009, Pages 334-336
Meat Science

High bacterial contamination of pig tonsils at slaughter

https://doi.org/10.1016/j.meatsci.2009.06.004Get rights and content

Abstract

Food-borne zoonoses have a major health impact in industrial countries. Campylobacter spp., Salmonella enterica, Yersinia enterocolitica and Listeria monocytogenes are high-risk food-borne zoonotic hazards in finishing pigs. The objectives of this work were (1) to study the isolation rate of pathogenic Y. enterocolitica, Salmonella spp., Campylobacter spp. and L. monocytogenes in the tonsils and feces and (2) to determine the number of mesophilic aerobic bacteria (MAB) and Escherichia coli in the tonsils of fattening pigs at slaughter. The samples, which were collected from one slaughterhouse on five occasions, originated from 50 pigs and 15 farms. The number of MAB varied from 6.40 to 7.82 log10 CFU/g and E. coli from 4.38 to 6.53 log10 CFU/g. Additionally, 31 (62%) of the tonsils were colonized with Y. enterocolitica and 16 (32%) with L. monocytogenes. Campylobacter spp. were more frequently excreted in feces and only 3 (6%) of the pigs carried Campylobacter spp. in the tonsils. No Salmonella spp. were isolated. The pig tonsils were shown to be colonized with a high number of bacteria including E. coli, which is the most important indicator for fecal contamination, and with Y. enterocolitica and L. monocytogenes, which are important food-borne pathogens. This study demonstrates that the tonsils are highly contaminated with micro-organisms and can be a very important source of contamination in the slaughterhouse.

Introduction

Food-borne zoonoses are infectious diseases of major health and economic significance in developed countries. They are most often acquired through ingestion of contaminated foods but they can also be acquired directly from animals. The two most frequently reported zoonotic diseases in humans in the EU in 2007 were Campylobacter and Salmonella infections with incidences of 120 and 31 cases per 100,000 inhabitants, respectively (EFSA, 2009). Yersinia and especially Listeria monocytogenes had lower incidences of 2.0 and 0.3 cases per 100,000 inhabitants, respectively. However, L. monocytogenes infection may be severe, especially in immunocompromised individuals with rather high fatality (Ramaswamy et al., 2007). A high proportion of human campylobacteriosis, salmonellosis, yersiniosis and listeriosis is likely to originate from pigs (Fosse, Seeger, & Magras, in press).

Pigs are mostly asymptomatic carriers of Salmonella enterica, Campylobacter spp., Yersinia enterocolitica and L. monocytogenes. All these bacterial pathogens have been isolated from the intestinal tract of pigs (Fosse et al., in press). However, pathogenic Y. enterocolitica has shown to be a more frequent inhabitant in pig tonsils (Bucher et al., 2008). L. monocytogenes is a ubiquitous organism occasionally present in the intestinal tract of various animal species but this pathogen has also been isolated from tonsils of fattening pigs (Autio et al., 2004). These pathogens can not be detected by macroscopic examination of carcasses during meat inspection.

S. enterica, Campylobacter spp., Y. enterocolitica and L. monocytogenes are food-borne zoonotic hazards which can be transmitted from pigs to humans through the consumption of pork which is today the most frequently consumed meat in Europe (Fosse et al., in press). Fosse, Seeger, and Magras (2008) have demonstrated that S. enterica, Y. enterocolitica and Campylobacter spp. are the three hazards most frequently reported in human clinical cases related to the consumption of pork. L. monocytogenes showed the highest severity score with high hospitalization and lethality rates (Fosse et al., 2008). In 2004, the prevalence rates of Campylobacter spp., Salmonella spp. and Yersinia spp. in pigs in the EU varied between 0.4–79.6%, 0.4–29.4% and 0.9–10.4%, respectively (Nørrung & Buncic, 2008). There was insufficient data available on the prevalence of L. monocytogenes in pigs (Nørrung & Buncic, 2008).

The objectives of this work were to (1) study the isolation rate of enteropathogenic Y. enterocolitica, Salmonella spp., Campylobacter spp. and L. monocytogenes in the tonsils and feces and (2) determine the number of mesophilic aerobic bacteria (MAB) and Escherichia coli in the tonsils of fattening pigs at slaughter.

Section snippets

Materials and methods

Tonsil and fecal samples were collected from 50 fattening pigs at slaughter in 2004. A slaughterhouse in Munich, Germany, was visited five times during January and March. At each visit, tonsil and fecal samples were taken from 10 pigs from at least three to four farms. In total, the pigs originated from 15 farms. The tonsils were collected using sterile plastic gloves and knives, and the fecal samples from the rectum in sterile plastic gloves. The samples were transported to the laboratory in

Results and discussion

The palatine tonsils are a well-known portal of entry and a site of multiplication and persistence for several micro-organisms in humans and animals including pigs (Salles & Middleton, 2000). In this study, the number of MAB and E. coli was very high in the tonsils of fattening pigs (Table 1). The mean number of MAB and E. coli was 7.12 log10 CFU/g and 5.52 log10, respectively. There was no significant difference in the mean number of MAB (p > 0.1, t-test) and E. coli (p > 0.05, t-test) between the

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