Amongst the bacteria causing urinary tract infections there is nothing more feared than Escherichia coli.

We can definitely award this tiny bacteria the title of Bladder Enemy #1.

The role E. coli plays in urinary tract pathology cannot be overstated; it is so important to medical research that it was defined as a separate category: Uropathogenic Escherichia coli or UPEC.

In fact, research about Escherichia coli is so vast and relevant, it will be addressed in future articles on our site.

Responsible of up to 90% of community acquired (non–hospital) urinary tract infection in both women and men, E. coli continues to puzzle scientists and doctors alike with its adaptability, strength, survival in extreme conditions, ease of connecting with biological tissues and super ability to build biofilms.

Escherichia coli is a typical gram-negative rod bacterium. Its dimensions are those of a cylinder 1.0-2.0 micrometres long, with radius about 0.5 micrometres (1)

To get an idea of size comparison: 1mm equals 1000 micrometres, or to put it differently, the length of an E. coli bacteria is about one thousandth of a millimetre.

Named after the German paediatrician and bacteriologist Theodore Escherich, the E. coli bacteria was first discovered and described in 1885.

 E.coli and related bacteria comprise only about 0.1% of intestinal flora (2) and the intestinal- oral mechanism is the main route of contamination in humans.

While many E. coli groups are not harmful in humans, there are several known strains extremely pathogenic, like E.coli 0157:H  that produce toxins damaging the red blood cells, causing severe food poisoning, and organ damage in particular in the elderly and vulnerable.

Uropathogenic E. coli (UPEC) is responsible for approximately 90% of urinary tract infections (UTI) in humans.

The majority of infections occur when ascending gut bacteria from stools colonize the urethra and ascend to the bladder, as well as the kidneys and prostate in males. 

These infections are called ascending urinary tract infections due to the access route. As women have a shorter urethra than men, they are over 10 times more likely to suffer from this type of infection.

Although the widely used term worldwide for all urinary tract infections is UTI, it is important to note that Bladder Infections are defined as Lower Urinary Tract Infections LUTI, or Cystitis, while the infections progressing to the kidneys are called Pyelonephritis.

The particular anatomy of Uropathogenic E. coli shows it’s cellular wall is covered with molecular hairs or filaments called fimbria or pili. These structures enable the bacteria to attach to the cells of the urinary tract lining called urothelium and colonise the bladder as well as the kidneys.

This adherence to the bladder lining cells is a crucial step during the infection that allows Uropathogenic E.coli to colonize the bladder and prevents bacterial being flushed out during urination

Apart from its anatomy, E. coli is a super adaptor bacteria that quickly adjusts to every type of environment with amazing speed.

It can survive in the presence or absence of oxygen, practically switching from aerobic to anaerobic metabolism according to the environment.

It can survive freezing temperatures by maintaining a state of hibernation and favour temperatures between 25-40 degrees Celsius.

It can adapt to both acidic and alkaline environments with amazing speed(3).

It survives at acidic pH values of 5 as well as alkaline mediums of over 10 pH.

Important research at Washington University, St Louis  found that contrary to the conventional wisdom in medicine, the idea that acidic urine is best for stopping bacterial growth is contradicted by research in how urinary pH affects bacterial growth(4).

Their results were surprising because samples that were less acidic, closer to the neutral pH of pure water, pH of 7-7.25 showed higher activity of a chemical compound called siderocalin, and were better at restricting bacterial growth than the acidic samples.

Importantly, the researchers also showed that they could encourage or discourage bacterial growth in urine simply by adjusting the pH of the urine samples they researched. This is a major finding that could have implications for how patients with UTIs are treated to limit bacterial growth.

This research is extremely important in dispelling the myth that an acidic pH can help in cases of urinary tract infections.

Still drinking cranberry juice for UTIs? Best not to, as urine acidity is actually bad for urinary tract infections as it speeds bacterial growth.