Escherichia coli: what it is, symptoms and prevention of infection

Escherichia coli is the name of a bacterium that lives in the intestine. In some cases it acts like a diner, in others it can cause problems

Index

  • Things?
  • Symptoms
  • Diagnosis
  • How to fight it
  • Transmission
  • Prevention

Things?

Escherichia coli is a bacterium that commonly lives in the intestine and that behaves most often as a diner. The adjective “diner” indicates how, in the coexistence relationship between two organisms, only one of the two benefits. At the same time, however, in order to be able to speak of commensalism, the other organism must not suffer damage from this coexistence. Therefore, Escherichia coli is a commensal since it exploits the nutrients present in the colon without causing any damage to the human body.

There are actually several strains of Escherichia coli and, among these, some can behave as pathogens because they possess such virulence characteristics as to be able to cause infections in the gastrointestinal tract or in other systems, in particular at the urinary level.

It is a gram-negative bacterium that belongs to the family of enterobacteria, so called because they find their ideal habitat in the intestines of humans and other animals. Escherichia coli has a typical rod shape and is equipped with flagella it uses to move and filaments called fimbriae it uses to communicate with other bacteria and to anchor itself to host cells. It has a facultative aerobic metabolism and this allows it to grow both in the presence and absence of oxygen. The optimal temperature for its survival is 35-40 ° C, which is why Escherichia coli lives very well in the human intestine.

In harboring Escherichia coli in our intestine we have gained some advantages: this bacterium, in fact, contributes to the correct digestion of food (or rather, of undigested food residues that reach the level of the colon) and to the synthesis of vitamin K. By virtue of these abilities, Escherichia coli is even considered by some to be a symbiotic microorganism (remember that we speak of symbiosis when two organisms gain mutual benefit from coexistence).

In some cases, however, Escherichia coli behaves as a pathogen and causes problems.

Symptoms

We could say that Escherichia coli is so versatile that it can behave as a commensal, as a symbiotic and ultimately as an opportunistic pathogen. The adjective “opportunist” indicates that this microorganism can take advantage of certain circumstances to multiply until it causes disease. In general, while Escherichia coli is harmless for healthy individuals, in subjects with a compromised immune response (such as burns, transplant recipients, AIDS patients) it can take over and cause sometimes serious diseases.

Some strains of Escherichia coli with adhesion structures that allow the bacterium to anchor itself to the membrane of the cells lining the bladder and urinary tract are defined uropathogenic. These bacterial strains are capable of causing urethritis, cystitis, prostatitis and in the most severe cases kidney infections. If these strains spread to the blood, they cause the appearance of extra-intestinal diseases such as meningitis, septicemia, peritonitis, pneumonia and infections affecting other internal organs.

The most frequent situation, however, remains that of enteritis, or an intestinal infection, which can cause episodes of hemorrhagic diarrhea with the emission of unformed stools mixed with blood.

Another important strain is certainly the enterotoxigenic Escherichia coli which, together with the enteropathogenic one, represents the most frequent causative agent of bacterial diarrhea and is also often implicated in the so-called traveler’s diarrhea. With this expression we refer to a form of diarrhea that affects travelers who go for tourism or for work in developing countries.

Diagnosis

Doctors can diagnose an Escherichia coli intestinal infection after asking a few questions about the symptoms and doing some tests. Stool examination is called coproculture. It is usually associated with an antibiogram, a fundamental step in understanding which antibiotics the bacterium is susceptible to. Molecular tests are also available which are useful for the serological research of toxins and for the determination of the bacterial serotype or the type of Escherichia coli involved in the infection.

How to fight it

Fortunately, the infection sustained by Escherichia coli in most cases resolves spontaneously without having to resort to particular drugs. For this reason the doctor often limits himself to recommending rest and a generous intake of liquids to replace the losses of water and mineral salts. Only in special cases is antibiotic therapy prescribed.

Transmission

Infections can be contracted through contact with both human and animal feces. Transmission therefore occurs mainly via the fecal-oral route. Bacteria can enter the body when you drink water or eat contaminated food. Recall that the presence of Escherichia coli in aquifers is a common indicator of faecal contamination. Faecal material can contaminate lakes, canals, swimming pools, or water supplies, and as a result, you can become infected by accidentally swallowing water while bathing.

A similar argument applies to foods, so much so that Escherichia coli is typically sought in the analyzes carried out by health inspectors in the field of collective catering. Food contamination can also occur during slaughter or meat preparation. If the meat is not properly cooked, the bacterium survives. It is important to know that Escherichia coli possibly present in minced meat resists the low cooking temperature to which burgers are subjected. Other foods at risk besides meat are vegetables and in particular lettuce, spinach and sprouts, but also unpasteurized fruit juices, raw milk and cheeses derived from unpasteurized milk. The bacterium can also be passed from one person to another. This is why it is important to wash your hands.

Prevention

Many E. coli infections could be easily prevented simply by improving general hygiene conditions.

  • First of all it is recommended to drink only potable water and this should be remembered especially when traveling to countries where the water is not treated. In these cases it is also important to avoid the consumption of ice and particular attention must be paid to the use of tap water to brush your teeth.
  • It is important to always wash your hands with warm soapy water, especially before preparing food or after touching raw meat, using the toilet or coming into contact with an animal.
  • Raw meat, especially minced meat, must always be cooked at a minimum temperature of 70 ° C for at least two minutes. It is important that even the innermost layers of meat reach this temperature for a sufficiently long time.
  • To avoid cross-contamination, raw meats must be prepared separately from cooked ones, avoiding the use of the same surfaces or utensils.
  • Plant foods such as fruit and vegetables should be washed with drinking water and peeled before consumption, especially if they are eaten raw. Finally, it is advisable to drink only milk, dairy products and pasteurized juices.
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