is well adapted to life in the guts of animals and birds, where it is often found in very high levels. However, to infect humans it also needs to be able to survive outside the gut, on the surface of meat that will be eaten by humans. It is known that C. jejuni
cannot grow under normal atmospheric conditions - the levels of oxygen are too high for it - so how it survives was until recently unknown. The mystery has now been solved by Friederike Hilbert and colleagues at the Institute of Meat Hygiene, Meat Technology and Food Science of the University of Veterinary Medicine, Vienna.
The surface of meat harbours a number of species of bacteria that - fortunately - are rarely harmful to humans, although they are associated with spoilage. It seems possible that the various species interact and Hilbert hypothesized that such interactions might help bacteria such as Campylobacter jejuni
survive under hostile, oxygen-rich conditions. She thus tested the survival of C. jejuni
in the presence of various meat-spoiling bacteria. When incubated alone or together with bacteria such as Proteus mirabilis or Enterococcus faecalis, Campylobacter
survived atmospheric oxygen levels for no longer than 18 hours. However, when incubated together with various strains of Pseudomonas
were found to survive for much longer, in some cases over 48 hours, which would be easily long enough to cause infection.
There were differences in the extent of prolonged survival depending on the sources of the Campylobacter
analysed 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 save the lives of the Campylobacter
Hilbert's findings show clearly that the presence of Pseudomonas
bacteria is responsible for significantly enhanced survival of the disease-causing Campylobacter
bacteria on the surface of meat. The results have implications for the control of meat, especially poultry, destined for human consumption. As Hilbert says, "On the basis of this study it should be possible to elucidate new mechanisms for limiting the level of Campylobacter
on chicken meat and thus the incidence of food poisoning could be much reduced."