Elsevier

Veterinary Microbiology

Volume 162, Issue 1, 22 February 2013, Pages 136-143
Veterinary Microbiology

Experimental infection of weaned piglets with Campylobacter coli – Excretion and translocation in a pig colonisation trial

https://doi.org/10.1016/j.vetmic.2012.08.016Get rights and content

Abstract

Campylobacter (C.) is one of the most common food-borne pathogen causing bacterial enteric infections in humans. Consumption of meat and meat products that have been contaminated with Campylobacter are the major source of infection. Pigs are a natural reservoir of Campylobacter spp. with C. coli as the dominant species. Even though some studies focussed on transmission of C. coli in pig herds and the excretion in faeces, little is known about the colonisation and excretion dynamics of C. coli in a complex gut microbiota present in weaned piglets and the translocation to different tissues.

Therefore, an experimental trial was conducted to evaluate the colonisation and translocation ability of the porcine strain C. coli 5981 in weaned pigs. Thus, ten 35 days old piglets were intragastrically inoculated with strain C. coli 5981 (7 × 107 CFU/animal) encoding resistances against erythromycin and neomycin. Faecal samples were taken and C. coli levels were enumerated over 28 days. All piglets were naturally colonised with C. coli before experimental inoculation, and excretion levels ranged from 104 to 107 CFU/g faeces. However, no strain showed resistances against the additional antimicrobials used. Excretion of C. coli 5981 was seen for all piglets seven days after inoculation and highest counts were detectable ten days after inoculation with 106 CFU/g faeces.

Post-mortem, translocation and subsequent invasion of luminal C. coli was observed for gut tissues of the small intestine and for the gut associated lymphatic tissues, such as jejunal mesenteric lymph nodes and tonsils as well as for spleen and gall bladder.

In conclusion, this pig colonisation trial offers the opportunity to study C. coli colonisation in weaned piglets using the porcine strain C. coli 5981 without the need for gnotobiotic or specific pathogen-free animals.

Introduction

Campylobacter (C.) spp. are one of the most dominant zoonotic bacterial cause of human enteritis. Infection results in clinical outcomes like diarrhoea, abdominal pain, and fever (Newell, 2001). Both species asymptomatically colonise the intestine of many farm animals but also wildlife and companion animals (Horrocks et al., 2009). Pigs are a natural reservoir of Campylobacter spp. (with Campylobacter coli predominating) with prevalence between 50% and 100%, and excretion levels ranging from 102 to 107 colony forming units (CFU)/g faeces (Alter et al., 2005, Jensen et al., 2006). Risk factors for the introduction of C. coli to pig herds largely remain unclear. It is assumed that horizontal transmission via farmers, domestic animals, contaminated surface water, insects, and other environmental sources are largely responsible for introduction into herds (Guerin et al., 2007, Wassenaar, 2011). Vertical transmission from mothers to offspring may occur via the faecal–oral route (Alter et al., 2005). Although C. coli are responsible for only 10% of human Campylobacter infections the impact on human health is still substantial (Wilson et al., 2008). C. coli can be transmitted from pigs to humans through the consumption of contaminated pork. The consumption of raw minced meat was identified as specific risk factor for C. coli infection (Gillespie et al., 2002).

The colonisation and excretion dynamics as well as the translocation ability into deep tissues of C. coli in pigs have not been thoroughly evaluated yet. A reason for this could be the high prevalence of C. coli in pigs. Subsequently high efforts would have to be made using gnotobiotic or specific pathogen-free (SPF) animals. However, such data are a prerequisite for assessing the risk of human C. coli infections derived from pork.

The objectives of this study were to investigate the (i) colonisation dynamics and (ii) excretion pattern and (iii) to describe C. coli translocation into different tissues by using a C. coli colonisation trial in weaned piglets.

Section snippets

Bacterial strains and inoculum preparation

The C. coli 5981 strain used in the trial was originally isolated from pig faeces in 2007. C. coli 5981 belongs to the ST-828 clonal complex and is a typical representative of porcine C. coli based on MLST analysis (Sheppard et al., 2010). In preliminary in vitro experiments we found that its pathogenic potential is comparable to C. coli ATCC 33559, as in infected human intestinal HT-29/B6 cells the epithelial integrity was disturbed by the induction of apoptosis. The strain C. coli 5981 was

Clinical examination and growth performance of pigs

All animals remained in very good health conditions throughout the study. No major changes in the faecal score could be recorded. The overall faecal consistency of score 4 (well-formed and solid) remained constant for 17 days p.i., then it slightly decreased to 3.5 for four days. After that, it reached the initial score again. Piglets showed normal growth performance, achieving a body weight of 22.8 ± 2.2 kg at the age of 63 days (28 days p.i.).

Enumeration of C. coli in faeces and excretion kinetics

In mother sows, C. coli could be detected for both

Discussion

This study demonstrates the ability of the porcine strain C. coli 5981 to colonise in the presence of a complex gut microbiota including other Campylobacter strains in weaned piglets. This particular strain was tracked along the GI tract and translocation of C. coli towards extra-gastrointestinal sites was detected. Nine out of ten piglets shed C. coli prior to inoculation at a mean value of 104 CFU/g faeces but no growth was detectable in media containing erythromycin and neomycin, suggesting

Conclusion

The inoculated C. coli 5981strain integrated well into the natural C. coli population of weaned piglets. The inoculation strain could be differentiated from naturally colonising C. coli by its two additional antibiotic resistances. We demonstrated the invasion into intestinal epithelial cells and translocation to extra-gastrointestinal sites for naturally colonising C. coli and to a lesser extent for the inoculation strain C. coli 5981. Only low numbers of C. coli were detectable in

Conflict of interest

The authors are solely responsible for the data and do not represent any opinion of neither the DFG nor other public or commercial entity.

Acknowledgments

The study was funded by the Deutsche Forschungsgemeinschaft (DFG) within the Collaborative Research Group 852 “Nutrition and intestinal microbiota-host interactions in the pig”. The technical assistance of In-Fah Lee is gratefully acknowledged.

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