Microbiology

What Disease does the Bacteria Campylobacter Jejuni cause and how



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Campylobacter jejuni is a highly motile, spiral shaped, gram-negative staining bacterium. Many birds carry the organism and it does not appear to cause any infection in avian species. Campylobacter is the most common cause of food poisoning in the developed world. Most of the cases of human campylobacteriosis are caused by the species Campylobacter jejuni although other species of Campylobacter sometimes cause infections. In addition to humans and birds, Campylobacter species infects many other animals such as cats, dogs and cows.

Most human pathogens have an optimal growth temperature of about 36 C (97 F). Campylobacter having evolved to use birds as a primary host has a higher optimal growth temperature of about 42 C (107.6 F). The organism requires a lower amount of oxygen for growth than many bacteria. However, it is not a strict anaerobe like the Clostridia bacteria that cause tetanus and gangrene.

Campylobacter species are very fragile bacteria. Normal atmospheric oxygen levels, freezing or drying out will all kill Campylobacter bacteria.

Any animal infected by or carrying campylobacter can pass the infection on to humans either through contact with infected fecal material (changing cat litter from an infected cat) or through undercooked meat and milk products. Campylobacter infections have been caused by undercooked meat from infected birds or animals and by contamination of cooked foods with raw meat. The ingestion of as few as 500 bacteria can cause gastroenteritis. Most cases of campylobacter food poisoning are associated with small family sized outbreaks or as isolated individual cases. Larger outbreaks of campylobacteriosis do occur and have been associated with water from sources that have been contaminated by birds or with unpasteurized milk from infected cattle.

The gastroenteritis associated with Campylobacter jejuni infection starts one to ten days after ingestion of the bacteria. The diarrhea may be bloody and can be accompanied by nausea and vomiting. Within the jejunum, ileum and colon the bacteria appear to invade and destroy the epithelial cells lining the intestines.

Complications with campylobacter are rare but immune suppressed people may develop systemic infections such as meningitis or myocarditis. About one in a thousand cases of campylobacteriosis develop the neurological condition Guillain-Barre syndrome. Persons suffering from Guillain-Barre syndrome frequently require hospitalization. In the United States, the CDC estimates that around 124 deaths a year are directly attributable to campylobacter infections.

Diagnosis of campylobacteriosis is by stool culture. The bacterial cultures are incubated at 42 C (107.6 F) in jars with gas producing packs, which yield an anoxic atmosphere. This culture method will give the maximum support to the growth of campylobacter species while inhibiting many other organisms. Growth of visible colonies may take from 24 to 48 hours.

Most cases of campylobacter do not require treatment with antibiotics. Patients are advised to drink plenty of fluids to maintain hydration. Occasionally severe cases of campylobacteriosis require treatment with antibiotics. Suitable antibiotics for such treatment include erythromycin or one of the fluoroquinolone antibiotics such as ciprofloxacin.

Standard hygiene and food safety measures will prevent campylobacter infections. Washing the hands before the preparation of food and after handling raw meat is essential. Meat, especially from poultry, must be cooked thoroughly before ingestion. Cooked foods must not be allowed into contact with raw meat or the surfaces where such meat has been prepared. Freezing meat can decrease the number of bacteria within the meat. Frozen meat must be completely defrosted before cooking. Water from any non-domestic supply such as a stream should be boiled before consumption. Milk and milk products are safe if they are pasteurized before ingestion.

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