Campylobacter jejuni
Campylobacter was not recognised as a cause of foodborne disease until the 1970s, and is now thought to be the main cause of foodborne disease in Australia. It is naturally present in the intestines of a number of different domestic animals and birds. It can be frequently isolated from the surface of poultry and also on the surface of cuts of raw meats. It has also been isolated from raw milk
The organism is sensitive to heat. Adequate cooking, reheating and control of cross contamination from raw foods to cooked foods are the primary control mechanisms in the kitchen. There have been a number of case investigations where salads have been implicated as the source of the organism. Transfer of the organisms to the salad vegetables from surfaces or implements used for raw meats being the most likely cause.
Description
Campylobacter species are slender spirally curved Gram-negative rods. The rods may have one or more spirals. They are non sporing and can form spherical bodies in stationary phase cultures. Campylobacter species are highly motile with a cork-screw motion by means of polar flagella at one or both ends.
They are oxidase and catalase positive and most species reduce nitrate. They grow under microaerophillic conditions and C. jejuni grows best in an oxygen concentration of 5-6% and 10% carbon dioxide. They are thermophilic organisms growing at temperatures ranging from 32oC to 45°C, with the optimum temperature 42°C. They can grow at pH values between 5.5 and 8.0. and one strain was capable of growth in the range pH 4.9-9.5
The organism is quite heat sensitive and treatments designed to kill salmonellae should destroy Campylobacter.
Characteristics of Illness
Campylobacteriosis is the name of the illness caused by C. jejuni, and is also known as campylobacter enteritis or gastroenteritis. It is caused by the bacterial cells adhering to the walls of the intestinal tract. There may be acute inflammatory enterocolitis and blood in the stools of patients caused by attachment of the organism to the cells of the intestinal wall and production of cytotoxin.
A dose of 500 cells of C. jejuni has been found to cause infection.
Illness usually occurs 2 to 7 days after ingestion of the contaminated food or water.
C. jejuni infection causes diarrhoea, which may be watery or sticky and sometimes bloody. Other symptoms may follow such as fever and abdominal pains.
Illness generally lasts 7-10 days and is generally self limiting, but relapses may occur in about 25% of cases.
Diagnosis of human illness
Diagnosis relies on isolating high number of C. jejuni from the diarrhoeal stools of individuals.
Complications
Complications are uncommon, however a small number of patients may suffer from Guillain-Barre syndrome which can occur 1-3 weeks after the illness. This is an auto-immune disease which attacks the peripheral nervous system causing flaccid paralysis which can last several weeks to months
Susceptible individuals
All age groups are susceptible, although children under five and young adults are more frequently afflicted.
Associated foods
The predominant foods implicated in outbreaks include raw chicken, raw milk and untreated water. Poor hygienic practices in food preparation has lead to other foods such as salads becoming contaminated.
Food analysis
Isolation of C. jejuni from food is difficult because the bacteria are usually present in very low numbers. Enrichment techniques are required. Media used to detect C. jejuni contains antibiotics and requires incubation at microaerophilic conditions. Isolation can take several days to a week.
Epidemiology
In 1996 an outbreak of campylobacteriosis occurred in a residential college in Australia. 40 people developed gastroenteritis. Although no food could be implicated it was thought the food had probably been contaminated by the students. As with Australia, C. jejuni is also the leading cause of bacterial diarrhoea in the USA. A large outbreak occurred in USA where 2,000 were affected. The source was traced to an untreated water supply. An outbreak of campylobacteriosis associated with the consumption of raw milk occurred in the USA, affecting 2,550 school children.
The number of outbreaks where poultry meat has been implicated is small however, there is evidence accumulating to implicate C. jejuni in sporadic cases. Serotyping of strains from poultry and humans has shown a similar distribution pattern. Risk analysis studies have identified consumption of poultry and handling of raw poultry during meal preparation as being high risk factors. It is thought that undercooking and cross contamination from raw poultry to ready to eat foods probably plays a major role in the spread of this disease.
It is thought that about 50% of infections are associated with either eating inadequately cooked chicken or re-contaminated chicken meat or handling raw chicken.
Case control studies in the US and the Netherlands failed to implicate red meat as a high risk factor in campylobacter enteritis.
Prevention
- Avoid cross-contamination by not using the same utensils and equipment for raw and cooked foods particularly poultry.
- Wash hands with soap regularly, particularly after going to the toilet and after handling raw foods.
- Thaw, store and cool perishable food in a refrigerator at less that 5°C.
- Heat food to above 75°C. Hold hot food at above 60°C.
- Avoid holding food in the danger zone between 50C-60ºC
Further Information
US Food and Drug Administration Bad Bug Book
Literature
- Hocking, A.D. et al. (2003). Foodborne Microorganisms of Public Health Significance. 6th ed. North Sydney. AIFST NSW Branch Food Microbiology Group.
- Doyle, M.P. (1989). Foodborne Bacterial Pathogens. Marcel Dekker; New York.