46E-20 |
The effects of the physicochemical surface characteristics of seven epidemic and fourteen sporadic Listeria monocytogenes strains on adhesion to glass |
M. S. CHAE and H. Schraft. Food Science, University of Guelph, Guelph, ON N1G 2W1, Canada Listeria monocytogenes serotype 4b (epidemic strains) have caused most large outbreaks of listeriosis while sporadic disease is due to strains of serotype 1/2 (sporadic strains). Serotype 4b may have better adhesion ability and subsequent survival in food processing environments, which results in a greater chance of contributing to post processing contamination of foods. Attachment to glass of seven epidemic and fourteen sporadic L. monocytogenes strains was examined. Epidemic strains had higher initial adhesion ability during 3h incubation (41.8–51.7%) than sporadic strains (29–47.08%). To better understand this difference in adhesion, cell surface hydrophobicity and extracellular carbohydrates of the 21 L. monocytogenes strains were studied. Cell hydrophobicity was measured by bacterial adherence to hydrocarbon (BATH) and by the polystyrene adherence method (PAM). Hydrophobicity of epidemic strains by BATH and PAM was 8–93%, 0.024-0.104 and that of sporadic strains was 5-66%, 0.02-0.128 respectively. Cell surface hydrophobicity measured by BATH was linearly correlated with PAM data (r2=0.8), but no correlation was found between hydrophobicity and bacterial attachment to glass. Cell surface hydrophobicity of epidemic strains was not significantly different from sporadic strains. Extracellular carbohydrates of planktonic cells and after 3h attachment were measured. After the initial 3h adhesion, attached cells were removed from the surface, suspended in buffer and centrifuged to obtain supernatant in which the concentration of extracellular carbohydrates was determined by colorimetric method. Planktonic cells were suspended in buffer and analyzed as adhered cells. Adhered epidemic strains contained significantly more carbohydrates (8.4-12.4 µg/Log CFU) than sporadic strains (6.3-10.4 µg/Log CFU) (p=0.003). In contrast, no significant difference was observed for planktonic cells. We suggest that the higher initial adherent ability of epidemic strains be caused by higher carbohydrate production during adhesion. This may increase the chance of epidemic L. monocytogenes to contribute to post processing contamination of foods.
Session 46E, International
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