Escerichia coli of Food Poisoning Infections

 

 

5.  Escerichia coli

 

The majority of E. coli in the GI tract are harmless unless they are displaced to other parts of the body such as the urinary tract or meninges. The pathogenic, or enterovirulent E. coli are divided into 4 groups according to their action in the body:

 

1.    Enteropathogenic (EPEC) - responsible for severe infantile diarrhoea.

 

2.    Enterotoxigenic (ETEC) - produces a heat labile (LT) or heat stable (ST) toxin. Both may be produced by the same organism. They are responsible for cases of paediatric diarrhoea, severe cholera-like illness, and traveller’s diarrhoea

 

3.    Enteroinvasive (EIEC) - pathogenicity is due to invasion of the gut mucosa. They give rise to a dysentery-like illness.

 

4.    Enterohaemorrhagic (EHEC) - responsible for bloody diarrhoea and colitis. It differs from bacillary dysentery in that fever is not prominent and the bloody discharges are copious rather than scanty. The O157:H7 had been implicated.

 

The pathogenic E. Coli can be differentiated from the non-pathogenic types by immunological and other methods. The incubation period is 12 hours to 3 days. The symptoms consist mainly of diarrhoea with blood and mucus in the stool. Infants acquire the infection by direct oral-faecal spread in maternal units and also by contaminated feeds. Enterotoxigenic E. Coli are prevalent in infants in tropical countries. Food and water in addition to faeces are sources of these organisms. The symptoms in adults are probably initiated by large doses of enterotoxigenic E. Coli producing heat stable toxin. E. Coli may enter kitchens in many raw foods and readily pass to cooked foods by hands, surfaces, containers and other equipment. They may also be water-borne also. During epidemics, human excreta may play a part in direct spread but unlike other gram-negative organisms, E. Coli will not survive long on the skin.

       Since E. Coli are always present in faeces, they are used as a marker for the faecal pollution of water, milk, and food. Intestinal pathogens such as Shigella and Salmonella may be found intermittently in water and sewage. However, they are only present in small numbers and thus difficult to find.

 

 

6.  Campylobacter jejuni

 

Campylobacter is commonly implicated in outbreaks involving predominantly children. The vehicle for transmission is usually raw or imperfectly pasteurized milk, and sometimes water. Isolation of the organism from poultry has been described frequently and infection occurs probably through the cross contamination from raw to cooked material. There may also be direct infection from the raw material to the food handler. The unusual conditions required to grow the organism have hindered its isolation and delayed epidemiological investigations. Person-to-person spread has been demonstrated and thus the dose level to initiate symptoms may be small.

       The onset of symptoms may be sudden with abdominal cramps followed by passage of foul-smelling stools. Blood and mucus may be present and the diarrhoea may persist for 1-3 days. A prodrome consisting of fever, headache, and dizziness may occur and this may last for a few hours to several days. The abdominal pain may persist once the diarrhoea has eased and symptoms may be more severe in adults than children. The incubation period is probably 3-5 days with a fairly wide range. Pet dogs and cats may be affected at the same time.

 

 

7.  Vibrio parahaemolyticus

 

V.  parahaemolyticus are reported to be responsible for 50% of food-poisoning incidents in Japan. In the warmer weather, it can be isolated from fish, shellfish, and other seafoods. Both raw and cooked seafoods such as shrimps, crabs, and lobsters are vehicles of infection. Cooked foods may be contaminated by the raw products in kitchens. Food poisoning following dinner parties with prawns on the menu are common. The illness resembles a mild form of cholera with an average incubation period of 15 hours. There is a rapid onset of symptoms with profuse diarrhoea often leading to dehydration, some vomiting , and fever. There is acute abdominal pain. The illness usually lasts 2-5 days. There are many serotypes.

 

 

8.  Aeromonas hydrophilia

 

Reports of outbreaks of A. Hydrophilia infections have come from India and Ethiopia. The organism was isolated from patients with diarrhoea. Long term surveys of diarrhoea in children and adults in the USA indicate both A. Hydrophilia and A. Sobria play significant roles. Water, milk, and seafoods were considered to be basic sources of the organism.