Escherichia coli in urine: reasons, symptoms, causes and treatment

By Cristiano Antonino On Apr 30, 2023

Escherichia coli in urine: under normal conditions, urine contains no bacteria. In certain situations, however, it may become colonised by pathogenic microorganisms

One of the most common is Escherichia coli, which can trigger a whole range of symptoms when it infects the urinary tract.

Here are what they are and how to intervene.

Escherichia coli, what it is

The name Escherichia coli or E. coli refers to a group of Gram-negative bacteria that are part of the normal intestinal flora and live in the intestine without causing problems, on the contrary, helping to keep the digestive tract healthy.

They play a fundamental role, participating in the digestion of food introduced in the diet.

It can happen, however, that this balance is broken and strains capable of triggering urinary tract infections, known as uropathogenic strains, end up taking over.

Escherichia coli in urine, the causes

Contamination of urine by Escherichia coli can occur via two routes: the endogenous, i.e. internal, and the exogenous, i.e. external, route.

The former is the most common way: in most cases, the problem arises when uropathogenic strains of Escherichia coli present in the intestines reach the urinary tract.

The latter, not being their natural environment, react to the ‘invasion’ by becoming inflamed and causing a series of disorders.

More rarely, microorganisms arrive from outside, for instance through unprotected sexual intercourse.

There are several reasons why Escherichia coli strains from the intestines can end up in urine.

First, there is an anatomical reason: the last tract of the intestine, i.e. the anal opening, is located close to the final part of the urinary tract, called the urethral meatus.

This proximity between the two districts favours the passage of bacteria.

Poor intimate hygiene and the habit of washing from year to year can also contribute to the problem.

Risk factors for Escherichia coli in urine

There are certain factors that increase the likelihood of urine being colonised by E. coli.

Here are the most common ones.

Female sex: In women, the urethra, the small tube that connects the bladder with the outside, is very short. It is, therefore, a very easy entry route for bacteria arriving from outside, for example from the partner, or from other areas of the body, such as the anus (the vaginal meatus is, in fact, very close to the latter, so it is possible for anal bacteria to colonise the bladder).

Sexual intercourse: through sexual intercourse, especially if unprotected, bacteria can be carried from outside to inside the urinary tract.

Constipation: this is a condition that slows down the transit of stools in the intestine, which then tend to stagnate in the last tract of the intestine. The possible consequence is the passage of faecal germs from the permeable wall of the intestine to the urinary tract.

Pregnancy: certain hormones typical of pregnancy (such as progesterone) cause the peristaltic activities of the smooth muscle, i.e. the involuntary contraction movements, of the bladder to slow down. Its function is therefore slowed down. This creates a stasis of urine in the bladder: an ideal condition for the proliferation of bacteria. In addition, the increased uterus volume compresses the bladder itself, which can no longer perform its functions properly. This results in further stagnation of urine. Finally, one must consider that during the nine months the intestinal transit slows down. This can lead to constipation, another condition conducive to the disorder.

Holding your pee: This is a bad habit that encourages urine stagnation in the bladder (which promotes bacterial growth) and makes urine too concentrated. These, on the contrary, should be expelled with some frequency to keep bacteria away.

Diabetes: this is a disease characterised by a high concentration of sugar in the blood. When values are particularly high, glucose is excreted through the urine, which does not normally contain it. Sugar, however, is a source of nutrition for bacteria, so its presence in the urine encourages bacterial proliferation.

Urinary catheter: this device, especially if used for a long time, increases the risk of urinary tract infections.

Escherichia coli urine and malformations

Among the risk factors for this problem are also anatomical malformations and lesions of the urinary tract, either present from birth or occurring later – e.g. as a result of another disease, surgery or the insertion of a catheter.

Almost all of them, in fact, create ideal conditions for the proliferation of bacteria.

Here are the main ones:

stenosis (narrowing) of the urethra;
spina bifida: congenital malformation of the neural cord, the organ from which the nervous system of the foetus is formed. It can lead to bladder dysfunction;
prolapse: downward fall of the bladder, due to the collapse of the muscles and decreased contractility of the bladder walls. The bladder never empties completely during urination, which encourages the development of bacteria;
disruption of the valve that connects the bladder to the urethra: thus small amounts of urine return to the bladder. The risk is that they also carry bacteria.

Escherichia coli in urine, symptoms

In many cases the presence of Escherichia coli in the urine triggers cystitis, i.e. an inflammation of the bladder.

Cystitis usually manifests itself acutely: the complaints come suddenly and within a few hours of the infection ‘breaking out’.

Here are the most common:

dysuria: difficulty urinating
stranguria: discomfort and pain during urination;
pollakiuria: increased number of urinations;
burning before and while urinating;
suprapubic pain: feeling of pain and heaviness above the pubis;
evening fever;
sometimes blood can be detected in the urine, due to the rupture of the most fragile capillaries.

However, there is also an asymptomatic form, in which the urine culture (the test that evaluates the presence of bacteria in the urine) is positive but there are no symptoms of urinary infection.

Tests for diagnosing Escherichia coli infection

To diagnose the presence of Escherichia coli in the urine, urinoculture, i.e. laboratory analysis of a urine sample, is used.

This investigation makes it possible to isolate the strains responsible for the infection and to assess, when combined with an antibiogram (further analysis of a urine sample), the sensitivity or resistance to antibiotics of the bacterial species involved in the patient.

This makes it possible to choose the most suitable antibiotic drug for the case.

Escherichia coli urine, treatment

Treatment varies depending on the situation.

In general, the asymptomatic form does not require treatment, except in pregnant women and people at risk.

However, it must be monitored over time.

Cystitis, on the other hand, must be treated

The treatment of choice is antibiotic therapy.

Among the most commonly used drugs are: fosfomycin trometamol, which can be administered in a single dose but cannot be used for long because many people develop resistance to this active ingredient; fluoroquinolones, which are very effective, but can cause gastro-enteric, musculoskeletal or neurological side effects; and β-lactams, a very broad category that includes several classes of antibiotics, including penicillin.

To limit bacterial resistance they are sometimes combined with a β-lactamase inhibitor.

As mentioned, the choice of drugs to be used should be made on the basis of the results of the antibiogram.

In the meantime, however, it is possible to resort to polypharmacy, i.e. taking several antibiotic molecules at the same time, to improve the situation and reduce the risk of emergence of resistant bacterial strains.

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