title: Effect of multiplicity of infection on Listeria monocytogenes pathogenicity for HeLa and Caco-2 cell lines.
abstract: The significance of multiplicity of infection (moi) for invasiveness and intracellular multiplication of Listeria monocytogenes in Caco-2 and HeLa cell monolayers was investigated. A low moi (1:1) resulted in recovery of significantly more L. monocytogenes when these bacteria were used to infect either cell line. At high moi (100:1), the percentage recovery of bacteria was comparatively low, even after extensive invasion and intracellular multiplication. Microscopic analysis of Giemsa- and immunofluorescent-stained infected monolayers revealed extensive cell disruption and exposure of the internalised bacteria to the bactericidal effect of gentamicin. By contrast, a low moi resulted in minimal cytopathic effects and evidence of cell to cell spread by L. monocytogenes was consistently observed in HeLa and J774, but not in Caco-2 cell lines. Nevertheless, the use of HeLa and Caco-2 cell monolayers enabled a clear distinction to be made between invasive (L. monocytogenes) and non-invasive Listeria spp. (L. innocua, L. ivanovii, L. seeligeri, L. grayi, L. welshimeri and L. monocytogenes LLO19). The use of a low moi with HeLa cell monolayers provided a reliable tissue-culture model of infection for L. monocytogenes.
authors.affiliation: Department of Microbiology and Immunology, University of Adelaide, South Australia.
authors.forename: M S
authors.initials: MS
authors.lastname: Francis
authors.forename: C J
authors.initials: CJ
authors.lastname: Thomas
mesh_terms: D018938:Caco-2 Cells / Q000382:microbiology*; D005455:Fluorescent Antibody Technique; D006367:HeLa Cells / Q000382:microbiology*; D006801:Humans; D008089:Listeria monocytogenes / Q000472:pathogenicity*