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Phagocytosis of Campylobacter jejuni and its intracellular survival in mononuclear phagocytes
Abstract:
In vitro phagocytosis and intracellular survival of Campylobacter jejuni strain 2964 in mononuclear phagocytes were studied. The following three types of mononuclear phagocytes were used: a J774G8 peritoneal macrophage line derived from BALB/c mice, resident BALB/c peritoneal macrophages, and human peripheral blood monocytes. When C. jejuni and mononuclear phagocytes were combined at a ratio of 75:1, light microscopy, fluorescent microscopy, and electron microscopy all indicated that C. jejuni cells were readily phagocytized. The majority of C. jejuni cells were spirals immediately following ingestion and were rapidly converted to the coccal form within 4 to 8 h. Conversion from the spiral form to the coccal form was complete in the presence of phagocytes within 96 h. In control preparations without phagocytes, conversion began after 24 h and was complete after 48 h. The extent of phagocytosis over time was determined by observing Giemsa-stained preparations and counting the number of intracellular bacterial colony-forming units after removal of extracellular C. jejuni. Human monocytes ingested C. jejuni more rapidly and vigorously than murine macrophages. Intracellular survival of C. jejuni was examined by measuring the number of C. jejuni colony-forming units associated with phagocytes after phagocytosis for 2 h and removal of extracellular bacteria. C. jejuni survived intracellularly for up to 6 to 7 days.
Insights
Campylobacter jejuni readily enters immune cells, transforming from spiral to coccal shapes within hours. This bacterium survives inside human monocytes and mouse macrophages for up to 7 days.
Area of Science:
- Microbiology
- Immunology
- Cell Biology
Background:
- Campylobacter jejuni is a leading cause of bacterial gastroenteritis worldwide.
- Understanding host-pathogen interactions is crucial for developing effective treatments.
Purpose of the Study:
- To investigate the in vitro phagocytosis and intracellular survival of Campylobacter jejuni in different mononuclear phagocytes.
- To characterize the morphological changes of C. jejuni within phagocytes.
Main Methods:
- Utilized J774G8 macrophage cell line, primary murine peritoneal macrophages, and human peripheral blood monocytes.
- Employed light, fluorescent, and electron microscopy to observe phagocytosis.
- Quantified intracellular C. jejuni via colony-forming unit assays and Giemsa staining.
Main Results:
- Campylobacter jejuni was readily phagocytized by all tested mononuclear phagocytes at a 75:1 ratio.
- C. jejuni rapidly converted from spiral to coccal forms within 4-8 hours intracellularly, completing conversion within 96 hours.
- Human monocytes demonstrated more rapid and vigorous phagocytosis compared to murine macrophages.
- Intracellular C. jejuni survived for up to 6-7 days within phagocytes.
Conclusions:
- Campylobacter jejuni effectively invades and survives within mononuclear phagocytes.
- The morphological transition to the coccal form is accelerated within host cells.
- Differences in phagocytic activity exist between human and murine mononuclear phagocytes, highlighting potential species-specific interactions.