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

Esteban JI, Oporto B, Aduriz G, Juste RA, Hurtado A - BMC Vet. Res. (2009)

Bottom Line: Positive samples were subcultured onto the selective and differential agar ALOA and biochemically confirmed.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.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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Animal Health, NEIKER - Instituto Vasco de Investigación y Desarrollo Agrario, Berreaga 1, 48160 Derio, Bizkaia, Spain. jesteban@neiker.net

ABSTRACT

Background: Listeria 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.

Results: Faecal 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.

Conclusion: 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.

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Related in: MedlinePlus

Dendrogram (UPGMA) of all the different L. monocytogenes ApaI PFGE patterns. Sources were coded as follows: S, sheep; DC, dairy cattle; BC, beef cattle.
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Figure 2: Dendrogram (UPGMA) of all the different L. monocytogenes ApaI PFGE patterns. Sources were coded as follows: S, sheep; DC, dairy cattle; BC, beef cattle.

Mentions: ApaI PFGE analysis performed on 68 isolates (24 from sheep and 44 from cattle) generated 40 patterns; 28 of them were unique patterns represented by single isolates only, and the remaining 12 included 2–8 isolates. Six patterns where shared by isolates obtained from sheep and cattle. However, isolates obtained from the sheep and cattle herd sharing the same farm premises (herds AS and AC) were clearly different according to their PFGE types (Table 2, Fig. 1). Serotype 1/2a isolates formed a separated cluster from the 4b complex isolates at similarity levels below 40% (Fig. 2). Diversity was high among 1/2a isolates (8 isolates, 8 patterns below 75% similarity), whereas for 4b isolates, 7 PFGE clusters (each containing 2–6 patterns) were observed at the 90% similarity level. Two of these clusters were represented by 14 and 15 isolates each, isolated from both sheep and cattle. The most prevalent pattern (LA-01, see Fig. 2) was isolated from a sheep herd, 2 beef cattle herds and 2 dairy cattle herds. Another pattern found in the three production systems was LA-08 (Fig. 2). The analysis of 24 ovine isolates from 16 herds generated 19 patterns, whereas in cattle 27 patterns were identified among the 44 isolates obtained from 24 herds. Most of the ruminant isolates analysed by PFGE had been isolated from faecal pools from different herds. However, in 6 herds several isolates originating from individual faecal samples were analysed and in 5 of them nearly all isolates (2–5 isolates/herd) had different patterns (Fig. 1, Table 2), demonstrating that several strains coexisted in the herds. Also interesting was to identify the same pattern in two dairy cattle herds (pattern LA-07 in Herds E & F, Fig. 1) located 63 km apart.


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

Esteban JI, Oporto B, Aduriz G, Juste RA, Hurtado A - BMC Vet. Res. (2009)

Dendrogram (UPGMA) of all the different L. monocytogenes ApaI PFGE patterns. Sources were coded as follows: S, sheep; DC, dairy cattle; BC, beef cattle.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2651128&req=5

Figure 2: Dendrogram (UPGMA) of all the different L. monocytogenes ApaI PFGE patterns. Sources were coded as follows: S, sheep; DC, dairy cattle; BC, beef cattle.
Mentions: ApaI PFGE analysis performed on 68 isolates (24 from sheep and 44 from cattle) generated 40 patterns; 28 of them were unique patterns represented by single isolates only, and the remaining 12 included 2–8 isolates. Six patterns where shared by isolates obtained from sheep and cattle. However, isolates obtained from the sheep and cattle herd sharing the same farm premises (herds AS and AC) were clearly different according to their PFGE types (Table 2, Fig. 1). Serotype 1/2a isolates formed a separated cluster from the 4b complex isolates at similarity levels below 40% (Fig. 2). Diversity was high among 1/2a isolates (8 isolates, 8 patterns below 75% similarity), whereas for 4b isolates, 7 PFGE clusters (each containing 2–6 patterns) were observed at the 90% similarity level. Two of these clusters were represented by 14 and 15 isolates each, isolated from both sheep and cattle. The most prevalent pattern (LA-01, see Fig. 2) was isolated from a sheep herd, 2 beef cattle herds and 2 dairy cattle herds. Another pattern found in the three production systems was LA-08 (Fig. 2). The analysis of 24 ovine isolates from 16 herds generated 19 patterns, whereas in cattle 27 patterns were identified among the 44 isolates obtained from 24 herds. Most of the ruminant isolates analysed by PFGE had been isolated from faecal pools from different herds. However, in 6 herds several isolates originating from individual faecal samples were analysed and in 5 of them nearly all isolates (2–5 isolates/herd) had different patterns (Fig. 1, Table 2), demonstrating that several strains coexisted in the herds. Also interesting was to identify the same pattern in two dairy cattle herds (pattern LA-07 in Herds E & F, Fig. 1) located 63 km apart.

Bottom Line: Positive samples were subcultured onto the selective and differential agar ALOA and biochemically confirmed.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.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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Animal Health, NEIKER - Instituto Vasco de Investigación y Desarrollo Agrario, Berreaga 1, 48160 Derio, Bizkaia, Spain. jesteban@neiker.net

ABSTRACT

Background: Listeria 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.

Results: Faecal 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.

Conclusion: 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.

Show MeSH
Related in: MedlinePlus