Faecal shedding and strain diversity of Listeria monocytogenesin healthy ruminants and swine in Northern Spain

Jon I Esteban,Ramón A Juste,Gorka Aduriz,Beatriz Oporto,Ana Hurtado

doi:10.1186/1746-6148-5-2

Jon I Esteban, Ramón A Juste + Show 3 more

Open Access

https://doi.org/10.1186/1746-6148-5-2

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Abstract

BackgroundListeria monocytogenes is among the most important foodborne bacterial pathogens due to the high mortality rate and severity of the infection. L. monocytogenes is a ubiquitous organism occasionally present in the intestinal tract of various animal species and faecal shedding by asymptomatically infected livestock poses a risk for contamination of farm environments and raw food at the pre-harvest stages. The aim of this study was to determine the prevalence and strain diversity of L. monocytogenes in healthy ruminants and swine herds.ResultsFaecal samples from 30 animals per herd were collected from 343 herds (120 sheep, 124 beef cattle, 82 dairy cattle and 17 swine) in the Basque Country and screened in pools by an automated enzyme-linked fluorescent immunoassay (VIDAS®) to estimate the prevalence of positive herds. Positive samples were subcultured onto the selective and differential agar ALOA and biochemically confirmed. L. monocytogenes was isolated from 46.3% of dairy cattle, 30.6% beef cattle and 14.2% sheep herds, but not from swine. Within-herd prevalence investigated by individually analysing 197 sheep and 221 cattle detected 1.5% of faecal shedders in sheep and 21.3% in cattle. Serotyping of 114 isolates identified complex 4b as the most prevalent (84.2%), followed by 1/2a (13.2%), and PFGE analysis of 68 isolates showed a highly diverse L. monocytogenes population in ruminant herds.ConclusionThese results suggested that cattle represent a potentially important reservoir for L. monocytogenes in the Basque Country, and highlighted the complexity of pathogen control at the farm level.

Highlights

Listeria monocytogenes is among the most important foodborne bacterial pathogens due to the high mortality rate and severity of the infection
These results suggested that cattle represent a potentially important reservoir for L. monocytogenes in the Basque Country, and highlighted the complexity of pathogen control at the farm level
L. monocytogenes was absent from all 17 porcine herds analysed, but present in cattle (30.6% of beef cattle and 46.3% of dairy cattle herds) and sheep (14.2%)

Summary

Introduction

Listeria monocytogenes is among the most important foodborne bacterial pathogens due to the high mortality rate and severity of the infection. Listeria monocytogenes is a ubiquitous organism that is occasionally present in the intestinal tract of various animal species and can cause severe illness in humans after the ingestion of contaminated food products. The widespread distribution of L. monocytogenes in nature and soil environments is favoured by its ability to grow in a wide range of temperature and pH [10]. This is important in silage production since in many cases the pH reached in the fermentation process is not low enough to prevent growth of L. monocytogenes [11]. Ruminants fed on silage are at higher risk of getting L. monocytogenes infection [12]

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