Heat tolerance of free living and of intracellular Listeria.
Listeria monocytogenes, L. innocua, and L. seeligeri are ingested by Tetrahymena pyriformis. They are not killed but survive and lyse bacteriovorous protozoans after about 8 days. The question important in food processing whether intracellular L. monocytogenes are protected against pasteurization was investigated using a model of Tetrahymena containing previously ingested Listeria. The study showed that Tetrahymena containing Listeria are more susceptible against application of heat, but intracellular Listeria, phagocytized within Tetrahymena, are not more protected than free and extracellular bacteria. Therefore, a properly performed pasteurization, i.e. of milk, kills intracellular Listeria as fast as extracellular living organisms. Finally, the pathogenic L. monocytogenes showed a higher susceptibility and lower tolerance against application of heat than apathogenic L. innocua and L. seeligeri.
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Staatliches Medizinaluntersuchungsamt Braunschweig.
Müller
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D000818:Animals; D006358:Hot Temperature; D008087:Listeria / Q000502:physiology*; D008089:Listeria monocytogenes / Q000502:physiology; D010587:Phagocytosis; D013768:Tetrahymena / Q000502:physiology*