| Summary: | Macrophages are phagocytic cells that play a key role in host immune response and clearance of microbial pathogens. <i>Porphyromonas gingivalis</i> is an oral pathogen associated with the development of periodontitis. Escape from macrophage phagocytosis was tested by infecting THP-1-derived human macrophages and RAW 264.7 mouse macrophages with strains of <i>P. gingivalis</i> W83 and 33277 as well as <i>Streptococcus gordonii</i> DL1 and <i>Escherichia coli</i> OP50 at MOI = 100. CFU counts for all intracellular bacteria were determined. Then, infected macrophages were cultured in media without antibiotics to allow for escape and escaping bacteria were quantified by CFU counting. <i>P. gingivalis</i> W83 displayed over 60% of the bacterial escape from the total amount of intracellular CFUs, significantly higher compared to all other bacteria strains. In addition, bacterial escape and re-entry were also tested and <i>P. gingivalis</i> W83, once again, showed the highest numbers of CFUs able to exit and re-enter macrophages. Lastly, the function of the <i>PG0717</i> gene of <i>P. gingivalis</i> W83 was tested on escape but found not related to this activity. Altogether, our results suggest that <i>P. gingivalis</i> W83 is able to significantly avoid macrophage phagocytosis. We propose this ability is likely linked to the chronic nature of periodontitis.
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