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Plasmid-mediated resistance to phagocytosis in Yersinia enterocolitica
Abstract:
Results of our previous studies have shown that the chemiluminescence response of human neutrophils (polymorphonuclear leukocytes [PMNs]) is inhibited by plasmid-mediated cell surface components from Yersinia enterocolitica. In this study we examined the susceptibility to phagocytosis of Y. enterocolitica cells with or without plasmid-mediated surface structure and the effect of isolated outer membrane fragments on phagocytosis of Escherichia coli by PMNs in vitro. Y. enterocolitica cells with expressed plasmid-mediated surface structure were much less sensitive to ingestion by PMNs than those without it, and the resistance to phagocytosis was readily eliminated in a dose-dependent fashion by pronase treatment of whole cells, which was shown to remove plasmid-encoded outer membrane proteins. Ingestion and intracellular killing of E. coli were inhibited significantly in the presence of isolated outer membrane fragments derived from plasmid-bearing Y. enterocolitica cells. To assess the interaction of Y. enterocolitica with phagocytic cells in vivo, two isogenic strains of Y. enterocolitica, differing only in the presence or absence of the virulence plasmid, were inoculated intradermally into the backs of rabbits; and tissue sections obtained at 12 h postinoculation were examined by light and electron microscopy. The plasmidless strain was found almost entirely in PMNs or mononuclear cells. In contrast, the plasmid-bearing strain was found to be surrounded by, or interspersed with, PMNs and mononuclear cells; but most bacteria were extracellular, with little evidence of phagocytosis. These results suggest that plasmid-mediated cell surface components of Y. enterocolitica act as antiphagocytic factors, thus facilitating the survival and proliferation of the organism in the host tissue.
Insights
Yersinia enterocolitica uses plasmid-mediated surface components to evade phagocytosis by human neutrophils (PMNs). These antiphagocytic factors protect the bacteria, aiding their survival and proliferation within host tissues.
Area of Science:
- Immunology
- Microbiology
- Bacterial Pathogenesis
Background:
- Human neutrophils (polymorphonuclear leukocytes [PMNs]) play a crucial role in host defense against bacterial infections.
- Previous studies indicated that Yersinia enterocolitica possesses plasmid-mediated components that inhibit PMN chemiluminescence.
Purpose of the Study:
- To investigate the role of plasmid-mediated surface structures of Yersinia enterocolitica in evading phagocytosis by PMNs.
- To determine the effect of isolated Y. enterocolitica outer membrane fragments on the phagocytosis of Escherichia coli by PMNs.
Main Methods:
- Comparative analysis of Y. enterocolitica's susceptibility to phagocytosis with and without plasmid-mediated surface structures.
- In vitro assays using isolated outer membrane fragments to assess their impact on PMN-mediated phagocytosis of E. coli.
- In vivo study in rabbits using isogenic Y. enterocolitica strains (plasmid-bearing vs. plasmidless) to examine bacterial-host cell interactions via light and electron microscopy.
Main Results:
- Y. enterocolitica expressing plasmid-mediated surface structures exhibited significantly reduced ingestion by PMNs compared to plasmidless strains.
- Pronase treatment, which removes plasmid-encoded outer membrane proteins, dose-dependently eliminated the resistance to phagocytosis.
- Isolated outer membrane fragments from plasmid-bearing Y. enterocolitica inhibited E. coli ingestion and intracellular killing by PMNs.
- In vivo, the plasmid-bearing Y. enterocolitica strain was predominantly found extracellularly with minimal phagocytosis, while the plasmidless strain was largely found within phagocytic cells.
Conclusions:
- Plasmid-mediated cell surface components of Yersinia enterocolitica function as potent antiphagocytic factors.
- These antiphagocytic mechanisms contribute to the survival and proliferation of Y. enterocolitica within host tissues, highlighting their importance in bacterial pathogenesis.