Escherichia Coli – an Overview
Escherichia coli is coliform bacterium of the genus Escherichia and is a Gram negative, facultative anaerobic, rod-shaped bacteria. E. coli lives a life of luxury in the lower intestines of warm blooded animals, including humans but when forced out, it lives a life of deprivation and hazard in water, sediment and soil. Most E. coli strain are harmless and are an important part of a healthy human intestinal tract. However, some E. coli are pathogenic cause either diarrhea or illness outside of the intestinal tract.
E. coli consists of a diverse group of bacteria. Pathogenic E. coli strains are categorized into pathotypes
Pathogenic subclasses of E. Coli
- Enterotoxigenic E. coli (ETEC)
- Enteroaggregative E. coli (EAGGEC)
- Enteropathogenic E. coli (EPEC)
- Enterohaemorrhagic E. coli EHEC
- Enteroinvasive E. coli (EIEC)
E. coli is very small. Its cells are rod-shaped, about 2.5 micrometers (mm) long. E. coli can survive in various soils for many months, even when moisture is limited.
Growth requirements: E. coli is a typical mesophile growing from 70C up to 500C with an optimum around 370C and at low pH of 3.6. Most of the strains are heat sensitive while some are heat resistant. It cannot grow below 0.90 water activity.
Both animals and people can be carriers of E. coli. This means they can be infected with the bacteria and can spread it to others without showing sign of illness
Animal reservoirs:- E. coli O157:H7 can be found in the fecal flora of a wide variety of animals including cattle, sheep, goats, pigs, cats, dogs, chickens, and gulls. The most important animal species in terms of human infection is cattle. EHEC and STEC are easily transmitted through contaminated water or food and, more rarely, through contact between animals and people. Thus, controlling outbreaks of these pathogens is a concern for the infectious disease community and the food industry.
You can be exposed to E. coli by:
- raw or undercooked beef, especially ground beef
- unpasteurized milk products, such as raw milk cheese
- food contaminated with the feces from infected animals or people
- contaminated food that has been improperly handled or undercooked
- contaminated raw fruits and vegetables, such as leafy greens or sprouts:
- unpasteurized juices
- unpasteurized (raw) milk
- mishandling or undercooking food contaminated with E. coli
- coming into contact with the feces of infected animals or people
Infants and young children (less than 5 years), pregnant women, older adults, and people with weakened immune are at high risk of getting infected. illness can range from mild to severe and life-threatening condition. E. coli O157:H7 infections exhibit a range of gastrointestinal seriousness. Young children infected with E. coli O157 are at highest risk for developing severe symptoms and complications, such as hemolytic uremic syndrome, which is a type of kidney failure. ETEC are considered to cause non-inflammatory watery diarrhea. The severity of diarrhea extends from asymptomatic infection to shock from massive enteric fluid loss; fever is unusual, but vomiting is not. EAEC infections have varied clinical features, which include acute and chronic watery diarrhea and occasionally bloody diarrhea with mucus, fever, nausea, vomiting, and abdominal pain. EAEC are related with pertinacious childhood diarrhea.
Onset are Duration
E.coli causes toxico-infection and the infectious dose is very low 1 to 200.Symptoms usually occur 3 to 4 days after a person comes in contact with E. coli O157. Most people get better within 5 to 7 days.