Most E. coli strains pose no harm to human health, except for serotype O157:H7, which can cause food poisoning in humans and can become life-threatening. Other less common serotypes, such as O104:H4, O121, O26, O103, O111, O145,and O104:H21 can also cause serious infection.
German pediatrician and bacteriologist, Theodor Escherich discovered the bacterium in 1885, hence its name. E. coli is now classified as part of the Enterobacteriaceae family of gamma-proteobacteria.
A healthy adult will usually make a full recovery from E. coli O157:H7 infection within 5 to 7 days. However, young children, elderly individuals and patients with weakened immune systems can develop potentially fatal HUS (hemolytic uremic syndrome), a type of kidney failure.
Signs and symptoms of E. coli O157:H7 infectionThe patient will typically experience symptoms within three to four days after being exposed to the bacteria, however, in some cases they may appear within a day or a week later.
The individual may experience:
- Abdominal pain - typically, the first symptom is severe abdominal cramping that comes on suddenly.
- Diarrhea - a few hours after the sudden abdominal pain, the patient typically has watery diarrhea. A day later there may be bright red bloody stools, caused by sores in the intestines.
- Vomiting - note that many patients who become ill may not vomit
- Fever - note that many infected people may not have a fever
- Fatigue - diarrhea causes loss of fluids and electrolytes (dehydration), making the patient feel sick and tired
What are the causes of E. coli O157:H7 infection?Most strains of E. coli are harmless. However, one group, including 0157:H7, produces a potent toxin - Shiga toxin - that is harmful for the lining of the small intestine.
Humans can become infected by:
- Ingesting contaminated water - even though tap water contains chlorine and has undergone ozone or ultraviolet treatment, some E. coli outbreaks have been caused by contaminated municipal water supplies. Private wells can be a source of infection, as can some lakes and swimming pools.
- Ingesting contaminated food - examples include ground beef, unpasteurized milk, or fresh vegetables. Infected people who work in restaurants and do not wash their hands properly after going to the toilet can spread the infection to customers and other members of staff.
- Having physical contact with an infected person, known as person-to-person contact. Good hand hygiene is important in stemming the spread of infection.
- Contact with animals - this may not only occur in farms, but also in petting zoos or country fairs.
E. coli infection risk factorsA risk factor is something which raises the chances of developing a condition or disease. For example, obesity significantly raises the risk of developing type 2 diabetes. Therefore, obesity is a risk factor for type 2 diabetes.
The following risk factors are linked to a higher risk of problems with E. coli infection:
- Certain foods - consuming soft cheeses, raw milk, apple juice, cider, and undercooked ground beef are linked to a higher risk of becoming ill
- Immunocompromised patients - those with weakened immune systems, such as patients with AIDS, those taking immunosuppressive medications, and people receiving chemotherapy are susceptible to complications.
- Stomach surgery - patients who have had the size of their stomach surgically reduced have less stomach acid that kills off bacteria.
- The person's age - very young children and elderly individuals have a higher risk of developing serious illness and complications
E. coli infection complicationsThe vast majority of infected individuals make a full recovery within a week. However, susceptible individuals (mentioned above) may develop hemolytic uremic syndrome (HUS).
Hemolytic uremic syndrome (HUS) - this condition is characterized by hemolysis (breakup of red blood cells) and kidney failure. Platelets, the red blood cells that are responsible for blood clotting, clump together within the small blood vessels of the kidneys, resulting in reduced blood flow (ischemia) and eventually leading to kidney failure. Decreased platelets also increase the risk of bleeding problems.
The patient can develop CNS (central nervous system) problems, including seizures, and can also go into a coma.
Kidney failure among infants and young children is usually caused by HUS.
Patients start off with E. coli infection symptoms - severe abdominal cramps, diarrhea which eventually becomes bloody, and nausea and vomiting (sometimes). While the majority of patients make a full recovery within a week to 10 days, approximately 6% go on to develop HUS. The majority are young children and elderly individuals. Between 3% to 5% of patients with HUS die, according to the National Institutes of Health, USA.
How is E. coli infection diagnosed?The doctor identifies the signs, asks the patients about symptoms, and sends a stool sample to a lab for analysis.
What are the treatment options for E. coli infection?No current treatments can cure E. coli O157:H7, it has to run its course.
Most doctors advise patients to get plenty of rest and drink lots of water to prevent dehydration.
The patient should avoid taking OTC medications for diarrhea, as all this will do is slow down the digestive system, undermining the body's ability to eliminate the toxins fast enough.
- Cook meat well - especially ground meat.
- Drinks - pasteurized milk, apple juice or cider are safer than unpasteurized.
- Wash vegetables - especially leafy green ones. Washing thoroughly might not protect you completely, but it helps.
- Wash cutlery and crockery - make sure knives, forks, plates and serving dishes are thoroughly washed with warm, soapy water.
- Store foods separately - use separate cutting boards, do not store raw ground beef right next to other foods.
- Hand hygiene - wash your hands thoroughly with warm water and soap after going to the toilet, before preparing foods, after preparing foods, and after touching animals. Wash your hands regularly.