Escherichia coli (commonly referred to as E. coli) is a species of bacteria commonly found in the intestines of humans and animals. There are many different types of E. coli, and while some live in the intestine quite harmlessly, others may cause a variety of diseases. The bacterium is found in faeces and can survive in the environment.
The commonest infection caused by E. coli is infection of the urinary tract, the organism normally spreading from the gut to the urinary tract. E. coli is also the commonest cause of cystitis (infection of the bladder), and in a minority of patients the infection may spread up the urinary tract to the kidneys, causing pyelonephritis. Otherwise healthy patients in the community may develop cystitis, and patients in hospital who have catheters, or tubes, placed in the urethra and bladder are also at risk. E. coli is also present in the bacteria that cause intra-abdominal infections following leakage from the gut into the abdomen, as for example with a ruptured appendix or following traumatic injury to the abdomen.
E. coli bacteria may also cause infections in the intestine. Diarrhoeal infections (intestinal) are caused by a group of E. coli known as 'enterovirulent' (harmful to the intestines).
Overspill from the primary infection sites to the bloodstream may cause blood poisoning ( E. coli bacteraemia). In rare instances, E. coli may cause meningitis in very young children.
Most people normally carry harmless strains of E. coli in their intestine. Both the harmless strains and the strains that cause diarrhoea are acquired primarily through ingestion of contaminated food or water. Person-to-person transmission is through the oral-faecal route.
To avoid getting strains capable of causing intestinal disease people should avoid eating undercooked meat, in particular inadequately cooked minced beef, and avoid drinking unpasteurised milk. Individuals working with uncooked meats or on farms should pay close attention to good hygiene practices, as should visitors to farms.
It is important to always wash your hands with soap or disinfectant after going to the toilet, and before and after handling food. Handwashing in young children should be supervised, especially after handling animals or their surroundings, for instance on a visit to a farm.
The risk of getting traveller's diarrhoea can be lowered by drinking only safe water (treated, boiled or sealed bottle), or by consuming ice known to be made from treated water. Food should be eaten freshly cooked and piping hot, salads should be avoided and fruit eaten only if it can be peeled.
The symptoms of E. coli infections vary according to the site of infection. For intestinal infections the symptoms may be diarrhoea, which can range from mild to profuse watery or bloody, cramps, nausea or vomiting.
Urinary tract infections are often characterised by a frequent urge to urinate and a painful burning sensation during urination; more severe infections involving the kidneys are often associated with back pain and fever.
Intestinal infections in young children can be particularly severe because they cannot tolerate much fluid and blood loss but all age groups are at risk e.g. of traveller's diarrhoea.
Urinary tract infections occur more commonly in females due to the close proximity of the anus and the urethra (the small tube to the bladder through which urine is released), and more frequently in the sexually active.
The elderly and people with compromised immune systems are more at risk from the infection, particularly bacteraemia.
E. coli infections can be diagnosed by the detection of E. coli in a laboratory test of your stool, urine, blood or other relevant sample. Infections with some types of E. coli, e.g. E. coli O157, can be detected by a serum antibody test.
Treatment depends on the type of infection. Intestinal infections are not usually treated with antibiotics and the mainstay of treatment involves drinking lots of water to avoid dehydration. In contrast, urinary tract or bloodstream infections are treated with antibiotics. The laboratory test should indicate which antibiotic is likely to be effective against the infecting strain.
Resistance rates vary according to the antibiotic. Prevalence rates of resistance to several antibiotics (e.g. amoxicillin/ampicillin, trimethoprim, fluoroquinolones and cephalosporins) have increased in recent years, particularly in severe infections, such as bacteraemia. Strains with cephalosporin resistance often produce Extended-Spectrum Beta-Lactamases (ESBLs) and are resistant to several antibiotics.