Effect of multiplicity of infection on Listeria monocytogenes pathogenicity for HeLa and Caco-2 cell lines
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1Department of Microbiology and Immunology, University of Adelaide, South Australia.
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.
Insights
A low multiplicity of infection (MOI) enhances Listeria monocytogenes recovery and cell-to-cell spread in tissue culture. This finding is crucial for developing reliable infection models for this bacterium.
Area of Science:
- Microbiology
- Cell Biology
- Infectious Diseases
Background:
- Listeria monocytogenes is an invasive bacterial pathogen.
- Understanding host-pathogen interactions is key to controlling infections.
- The multiplicity of infection (MOI) can influence bacterial invasion and intracellular growth.
Purpose of the Study:
- To investigate the impact of MOI on Listeria monocytogenes invasion and intracellular multiplication.
- To evaluate the utility of Caco-2 and HeLa cell monolayers as models for L. monocytogenes infection.
- To differentiate invasive L. monocytogenes from non-invasive Listeria species.
Main Methods:
- Infection of Caco-2 and HeLa cell monolayers with L. monocytogenes at varying MOIs (1:1 and 100:1).
- Quantification of bacterial recovery post-infection.
- Microscopic analysis (Giemsa and immunofluorescence staining) of infected monolayers.
- Assessment of cytopathic effects and bacterial spread.
Main Results:
- A low MOI (1:1) significantly increased L. monocytogenes recovery compared to a high MOI (100:1).
- High MOI led to extensive cell disruption and bacterial exposure, reducing recovery.
- Cell-to-cell spread was observed in HeLa and J774 cells at low MOI, but not in Caco-2 cells.
- HeLa and Caco-2 cells distinguished invasive L. monocytogenes from non-invasive Listeria species.
Conclusions:
- Low MOI is critical for efficient recovery and observation of intracellular multiplication of L. monocytogenes in cell culture.
- HeLa cell monolayers infected at low MOI provide a reliable model for studying L. monocytogenes infection.
- This study highlights the importance of MOI in bacterial pathogenesis studies and diagnostics.