Emerging Human Pathogen Photorhabdus asymbiotica Is a Facultative Intracellular Bacterium and Induces Apoptosis of Macrophage-Like Cells

Photorhabdus species are gram-negative entomopathogenic bacteria of the family ENTEROBACTERIACEAE: Among the different members of the genus, one species, Photorhabdus asymbiotica, is a pathogen of both insects and humans. The pathogenicity mechanisms of this bacterium are unknown. Here we show that...

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Bibliographic Details
Published in:Infection and Immunity 2009-03, Vol.77 (3), p.1022-1030
Main Authors: Costa, S.C.P, Girard, P.A, Brehélin, M, Zumbihl, R
Format: Article
Language:English
Subjects:
Apoptosis - physiology
Bacteria
Bacterial Infections
Bacteriology
Biological and medical sciences
Enterobacteriaceae
Enterobacteriaceae Infections - microbiology
Fundamental and applied biological sciences. Psychology
Humans
Life Sciences
Macrophages - microbiology
Macrophages - pathology
Microbiology
Microscopy, Electron, Transmission
Miscellaneous
Photorhabdus
Photorhabdus - pathogenicity
Photorhabdus - physiology
Photorhabdus asymbiotica
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Summary:Photorhabdus species are gram-negative entomopathogenic bacteria of the family ENTEROBACTERIACEAE: Among the different members of the genus, one species, Photorhabdus asymbiotica, is a pathogen of both insects and humans. The pathogenicity mechanisms of this bacterium are unknown. Here we show that P. asymbiotica is a facultative intracellular pathogen that is able to replicate inside human macrophage-like cells. Furthermore, P. asymbiotica was shown for the first time in an intracellular location after insect infection. We also demonstrated that among Australian and American clinical isolates, only the Australian strains were able to invade nonphagocytic human cells. In cell culture infection experiments, Australian clinical isolates as well as cell-free bacterial culture supernatant induced strong apoptosis of a macrophage cell line at 6 h postinfection. American isolates also induced cellular death, but much later than that induced by Australian ones. Mammalian cultured cells analyzed for key features of apoptosis displayed apoptotic nuclear morphology, activation of the initiator caspases 8 and 9 and the executioner caspases 3 and 7, and poly(ADP-ribose) polymerase proteolysis, suggesting activation of both the intrinsic and extrinsic apoptotic pathways.
ISSN:0019-9567
1098-5522
DOI:10.1128/IAI.01064-08