Escherichia coli or E.coli is a group of bacteria that has a close relationship with humans. Several strains of E.coli naturally live in the bowels of humans and other animals and it is passed out in large amounts in the stool. Although harmless when its population is controlled in the bowel, E.coli has the potential for causing serious diseases. It may infect the bowels, urinary tract, lungs, brain lining (meninges) and just about any other site that it gains entry to. However, the vast majority of E.coli outbreaks involves inflammation of the small and large intestines leading to symptoms such as diarrhoea.
Types of E.coli
There are several types of E.coli which are grouped according to its pathogenesis. Some may attach to the lining of the bowel and damage the mucosal cells. Others may secrete toxins that have the same effect. Certain strains may have both effects – attaches to the lining of the intestine and secretes toxins. These strains are known as :
- Enterotoxigenic E.coli (ETEC)
- Enteropathogenic E.coli (EPEC)
- Entero-invasive E.coli (EIEC)
- Entero-aggregative (EAggEC) and Enteroadherent E.coli (EAEC)
- Enterohaemorrhagic E.coli (EHEC)
All these strains cause diarrhoea. However, it is the EHEC (enterohaemorrhagic E.coli) that is of greater interest during outbreaks. These strains secrete an enterotoxin known as a verotoxin or Shiga-like toxin. It is therefore also referred to as verocytotoxic E.coli (VTEC) or Shiga-toxin E.coli (STEC). These E.coli bacteria have a predilection for the large intestine and causes bloody diarrhea. There are several O-serotypes of EHEC but these are broadly grouped as O157 and non-O157 because of the severity of E.coli O157 infection. Most outbreaks are due to the O157 serotype,, however, the 2011 E.coli outbreak in Europe was associated with the new O104 strain.
Spread of E.coli
E.coli diarrhea is transmitted by the orofaecal route meaning that if faecal particles containing E.coli enters through the mouth, it will then cause infection. This is one of the reason that outbreaks are so common among people frequenting the same eating establishment, especially if the food workers do not wash their hands or practice proper hygiene in the kitchen.
A significant percentage of many animals, particularly cattle, excrete faeces laden with STEC E.coli. Surface contamination of the meat may occur at the slaughter and processing stage and if the meat is undercooked, it can infect a person who eats it. In the kitchen setting, meat that may come into contact with vegetables that are to be eaten raw may also pass on the pathogen.
Sometimes E.coli is found in vegetables which have had no contact with meat. This may occur when run-off water from a pasture housing animals like cattle irrigates neighbouring fields used for growing vegetables. E.coli from the faeces of these animals will then spread and contaminate the vegetables, which if eaten raw, can cause diarrhoea in humans.
Less frequently, E.coli may contaminate milk and dairy products or be picked up directly from contact with contaminated soil. The latter is more likely to be see with farm workers and children who play in fields that previously housed cattle.
Signs and Symptoms of E.coli Infection
The clinical presentation may vary based on the area infected. If E.coli infects the lining of the brain and spinal cord, it causes meningitis (read more on meningitis symptoms), in the lungs it will cause pneumonia (fever, persistent cough, difficulty breathing) and the genitalia may cause urinary tract infections (burning upon urination, frequent urination, discharge, offensive smelling urine, fever).
The more common presentation, however is enterocolitis (inflammation of the small and large intestine). This leads to diarrhoea which can vary from profuse and watery, or even bloody, stool. Abdominal pains and intestinal cramps usually accompany the diarrhoea, but other symptoms like nausea, vomiting and fever may be mild or even absent. This should be differentiated from gastroenteritis (stomach flu) which is more often caused by viruses.
Treatment of E.coli Infection
The incubation period for E.coli infection range from 1 to 7 days, with most symptoms appearing by day 3 to 4. It usually resolves within a few days but may take up to 7 to 10 days. Antibiotics will be required in most cases of E.coli infection, however, with E.coli diarrhea it may not be necessary if a person is healthy, keeps themselves rehydrated and is showing signs of quick recovery. The bowels are able to restore its normal microenvironment and eradicate most invading pathogens but if necessary, your doctor will prescribe the appropriate antibiotic. Patients with a low immune system, like those with HIV/AIDS and severely debilitated patients, may need antibiotics immediately.
Prevention of E.coli Infection
Preventative measures may involve :
- frequent washing of hands with an appropriate antibacterial soap and regular use of a hand sanitizer.
- keeping raw meat and vegetables that are to be eaten raw separate from each other.
- thoroughly cook meat, particularly beef, at least above 50 degrees Celsius.
- avoid eating in food outlets that are not reputable and be cautious of street vendors.