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Appl Environ Microbiol. 2015 Aug 15;81(16):5604-12. doi: 10.1128/AEM.01031-15. Epub 2015 Jun 12.

Protozoan Cysts Act as a Survival Niche and Protective Shelter for Foodborne Pathogenic Bacteria.

Author information

1
Department of Veterinary Public Health and Food Safety, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium.
2
Nematology Research Unit, Department of Biology, Ghent University, Ghent, Belgium.
3
Laboratory of Protistology and Aquatic Ecology, Department of Biology, Ghent University, Ghent, Belgium.
4
Department of Veterinary Public Health and Food Safety, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium Kurt.Houf@UGent.be.

Abstract

The production of cysts, an integral part of the life cycle of many free-living protozoa, allows these organisms to survive adverse environmental conditions. Given the prevalence of free-living protozoa in food-related environments, it is hypothesized that these organisms play an important yet currently underinvestigated role in the epidemiology of foodborne pathogenic bacteria. Intracystic bacterial survival is highly relevant, as this would allow bacteria to survive the stringent cleaning and disinfection measures applied in food-related environments. The present study shows that strains of widespread and important foodborne bacteria (Salmonella enterica, Escherichia coli, Yersinia enterocolitica, and Listeria monocytogenes) survive inside cysts of the ubiquitous amoeba Acanthamoeba castellanii, even when exposed to either antibiotic treatment (100 μg/ml gentamicin) or highly acidic conditions (pH 0.2) and resume active growth in broth media following excystment. Strain- and species-specific differences in survival periods were observed, with Salmonella enterica surviving up to 3 weeks inside amoebal cysts. Up to 53% of the cysts were infected with pathogenic bacteria, which were located in the cyst cytosol. Our study suggests that the role of free-living protozoa and especially their cysts in the persistence and epidemiology of foodborne bacterial pathogens in food-related environments may be much more important than hitherto assumed.

PMID:
26070667
PMCID:
PMC4510183
DOI:
10.1128/AEM.01031-15
[Indexed for MEDLINE]
Free PMC Article

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