Campylobacter jejuni is a gram-negative curved motile rod. It is a microaerophilic organism, which means it has a requirement for reduced levels of oxygen. It is relatively fragile. Because of its microaerophiliac characterisitcs, the organism requires 3 to 5% oxygen and 2 to 10% carbon diozide for optimal growth conditions. This bacterium is now recognized as an important enteric pathogen. It was previously believed to be primarily an animal pathogen causing abortion and enteritis in sheep and cattle until methods were developed for its isolation in 1972. It is now recognized to be the leading cause of bacterial diarrhoeal illness in the US. C. jejuni is not carried by healthy adults but is found in healthy cattle, chickens, birds, and even flies. It is sometimes present in non-chlorinated water sources such as streams and ponds.
C. jejuni causes diarrhoea, cramps, nauea, headache, and fever. The diarrhoea may be watery or sticky and occult blood may be present. The illness usually occurs 2-5 days after ingestion of contaminated food or water. The illness generally lasts 7-10 days but relapses may occur in about 25% of cases. Most infections are self-limiting and do not require treatment with antibiotics. However, treatment with erthryomycin does reduce the length of excretion. The infective dose of C. jejuni is small. 400-500 bacteria may cause illness in some individuals. The pathogenic mechanisms are not fully understood and it does produce a heat-labile toxin that may cause diarrhoea.
C. jejuni frequently contaminates raw chicken. Surveys show that 20 to 100% of retail chickens are contaminated. This is not surprising since many healthy chickens carry these bacteria in their GI tract. Raw milk is also a source of infection. The bacteria are often carried by healthy cattle and by flies on the farms. Children under 5 and young adults are more frequently afflicted than other age groups.
Isolation of C. jejuni from food is difficult because the bacteria are usually present in very low numbers. A microaerophiliac atmosphere is required with antibiotic-containing selective media.