Campylobacter Rely on Pseudomonas to Infect Humans

The interaction between the different species of bacteria seems to be a mechanism for Campylobacter jejuni to remain viable and survive ambient oxygen levels.

C. jejuni is a microaerophilic gram-negative bacillus that causes febrile diarrhea or dysentery; vomiting or bloody stool are often noted with severe abdominal pain. The disease is most common among children and lasts one to four days.

Although Campylobacter infections are rarely life threatening, they are extremely debilitating and they have been linked with the development of Guillain-Barré syndrome, one of the leading causes of nontrauma-induced paralysis worldwide. The bacteria do not grow well at room temperature or in an oxygen-rich environment as it well adapted to life in the intestines of animals and humans. However, it is normally transmitted from contaminated chicken meat, as it is frequently found in the intestines of chickens, where it apparently does not result in any symptoms.

Scientists at the University of Veterinary Medicine (Vienna, Austria), have recently discovered that interactions with other bacteria allow C. jejuni to survive under hostile, oxygen-rich conditions. Campylobacter survived atmospheric oxygen levels for no longer than 18 hours when incubated alone or together with bacteria such as Proteus mirabilis, Citrobacter freundii, Micrococcus luteus or Enterococcus faecalis. However, when incubated together with various strains of Pseudomonas, Campylobacter were found to survive for much longer, in some cases over 48 hours, which would be easily long enough to cause infection. An in vitro assay was used to test the bacteria's survival rate.

There were differences in the extent of prolonged survival depending on the sources of the Campylobacter analyzed, but all isolates of all strains clearly survived significantly longer in the presence of Pseudomonas bacteria than when cultured alone. And the Campylobacter cells did not change shape when cultured together with Pseudomonas under oxygen-rich conditions, unlike when they were cultured alone, providing further indications of an interaction between the species. Interestingly, there is no evidence that the Pseudomonas benefit at all from the interaction, although they effectively facilitate the survival of Campylobacter under adverse conditions.

This microbial commensalism was diverse in C. jejuni isolates from different sources: isolates from chicken meat and humans in coculture with Ps. putida were able to use this survival support better than fecal isolates from broilers. Scanning electron microscopy revealed the development of fiber-like structures braiding Ps. putida and C. jejuni cells. Hence, it seems that microaerophilic C. jejuni is able to survive ambient atmospheric oxygen tension by metabolic commensalism with Pseudomonas species. This bacterial-bacterial interaction might set the basis for the survival of C. jejuni on chicken meat and thus be the prerequisite step in the pathway towards human infection. The study was published the October 2010 issue of Applied and Environmental Microbiology.

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