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Food-Info.net> Topics > Food Safety > Bacteria > Overview of food-borne bacteria
Campylobacter jejuni is a Gram-negative slender, curved, and motile rod. It is a microaerophilic organism, which means it has a requirement for reduced levels of oxygen. It is relatively fragile, and sensitive to environmental stresses (e.g., 21% oxygen, drying, heating, disinfectants, acidic conditions). Because of its microaerophilic characteristics the organism requires 3 to 5% oxygen and 2 to 10% carbon dioxide for optimal growth conditions. This bacterium is now recognized as an important enteric pathogen. Before 1972, when methods were developed for its isolation from faeces, it was believed to be primarily an animal pathogen causing abortion and enteritis in sheep and cattle.
C. jejuni is the leading cause of bacterial diarrhoeal illness in Europe. It causes more disease than Shigella spp. and Salmonella spp. combined.
Although C. jejuni is not carried by healthy individuals in the United States or Europe, it is often isolated from healthy cattle, chickens, birds and even flies. It is sometimes present in non-chlorinated water sources such as streams and ponds.
Because the pathogenic mechanisms of C. jejuni are still being studied, it is difficult to differentiate pathogenic from non-pathogenic strains. However, it appears that many of the chicken isolates are pathogens
Campylobacteriosis is the name of the illness caused by C. jejuni. It is also often known as campylobacter enteritis or gastroenteritis.
C. jejuni infection causes diarrhoea, which may be watery or sticky and can contain blood (usually occult) and faecal leukocytes (white cells). Other symptoms often present are fever, abdominal pain, nausea, headache and muscle pain. The illness usually occurs 2-5 days after ingestion of the contaminated food or water. Illness generally lasts 7-10 days, but relapses are not uncommon (about 25% of cases). Most infections are self-limiting and are not treated with antibiotics. However, treatment with erythromycin does reduce the length of time that infected individuals shed the bacteria in their faeces.
The infective dose of C. jejuni is considered to be small. Human feeding studies suggest that about 400-500 bacteria may cause illness in some individuals, while in others, greater numbers are required. A conducted volunteer human feeding study suggests that host susceptibility also dictates infectious dose to some degree. The pathogenic mechanisms of C. jejuni are still not completely understood, but it does produce a heat-labile toxin that may cause diarrhoea. C. jejuni may also be an invasive organism.
C. jejuni is usually present in high numbers in the diarrhoeal stools of individuals, but isolation requires special antibiotic-containing media and a special microaerophilic atmosphere (5% oxygen). However, most clinical laboratories are equipped to isolate Campylobacter spp. if requested.
C. jejuni frequently contaminates raw chicken. Surveys show that 20 to 100% of retail chickens are contaminated. This is not overly surprising since many healthy chickens carry these bacteria in their intestinal tracts. Raw milk is also a source of infections. The bacteria are often carried by healthy cattle and by flies on farms. Non-chlorinated water may also be a source of infections. However, properly cooking chicken, pasteurising milk, and chlorinating drinking water will kill the bacteria.
Total prevention is probably not possible, however properly stored, heated and cooked foods are generally safe. The largest risk is cross-contamination, where cooked material comes into contact with raw produce or contaminated materials (cutting boards).
Although anyone can have a C. jejuni infection, children under 5 years and young adults (15-29) are more frequently afflicted than other age groups.
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