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February 16, 2020
Urinary Tract Infection

Vaginal Bacterium Found To Trigger Recurrent Urinary Tract Infection


  • Scientists have found that recurrence of UTI is not solely due to the growth of E.coli
  • The presence of Gardnerella vaginalis was found to increase chances of recurrence in 50% of study population
  • Gardnerella vaginalis present in the urine should be taken as an indicator of another bout of UTI

Urinary tract infection (UTI) is found to affect nearly half of all women but a quarter of them could get the infection again after 6 months, according to a study by a research team from the University School of Medicine, St. Louis. The study published in PLOS Pathogens has identified a particular type of vaginal bacteria which infects the urinary tract.

Urinary Tract Infection (UTI):

Urinary tract infections occur when bacteria present in the bowel move into the urinary tract. These infections record an incidence of more than 8.1 million every year with a prevalence of 10 among 25 women and 3 among 25 men.

‘After initial UTI, Ecoli are present in reservoirs in the bladder and are triggered by Gardnerella vaginalis , leading to recurrence of UTI.’

There are two types of urinary tract infections — lower UTI and Upper UTI. UTI that affect the bladder or the urethra are called lower UTI, the symptoms include:

  • Pain while passing urine
  • Increased urge to pass urine
  • Abdominal pain
  • Cloudy urine, which is foul smelling and could contain blood
  • A general feeling of tiredness

UTI that affect the kidney or the ureters are called upper UTI. The symptoms include:

  • Fever
  • Shivering
  • Pain in the sides or the back
  • Restlessness

Lower UTI is not very serious and occur often, but upper UTI should be treated early as it could affect the kidneys.
The infections may be treated with an antibiotic but there could be a recurrence. It has been found that E.Coli is found to cause UTI in 80% of sexually active women. It was always believed that there was a re-occurrence of UTI when E.coli was re-introduced into the urinary tract.

Study Finding

The current study has found that there could be a new mechanism by which subsequent infection occurred. The bacterium present in the vagina Gardnerella vaginalisstimulates theE. coliwhich are already present in the bladder to cause UTI. This deadly bacterium Gardnerella vaginaliscould also lead to potentially serious kidney infections, according to the study.

  • Gardnerella vaginalis, the vaginal bacterium did not cause the urinary tract infection.
  • The bacterium damaged the cells that were present on the surface of the bladder.
  • This resulted in the growth of E.coli, that were already present, to result in the recurrence of UTI

Dr. Amanda Lewis who is with Washington University as an assistant professor of molecular microbiology and of obstetrics and gynecology said, that Gardnerella vaginalis laid the grounds for another infection by E.coli. Studies that were conducted earlier had shown that E.coli built dormant spaces in the bladder and could be re-activated to result in an infection. Gardnerella vaginaliscould be one of the triggers.

Finding the Trigger for Recurrence of E.coli Infection:

In the study, the bladders of female mice were infected with E.coli by the scientists, which lead to UTI. The scientists waited for the mice to recover from the infection. At the end of this stage the scientists found that there was no E.coli present in the urine.

However, earlier studies had shown that E.coli populations, though small in number, still persisted in the bladder and were undetectable in the urine.

In the next stage of the study, the scientists introduced

  • Lactobacillus crispatus, a normal commensal of the vagina
  • Gardnerella vaginalis, which is associated with bacterial vaginosis
  • Sterile salt water was used as control

The scientists found that

  • Both Lactobacillus crispatus and Gardnerella vaginalis were removed from the bladder within 12 hours.
  • E.coli re-appeared in the urine of nearly 50% of mice that were infected with Gardnerella vaginalis, which is associated with a re-occurrence of UTI.
  • Among mice that were administered with salt water, they were 5 times less likely to develop recurrent UTI.

The study found that though there was no re-introduction of E.coli into the mice, they began to grow from reservoirs that were present in the bladder. Another significant finding of the study involved the movement of E.coli from the bladder into the urinary tract and finally into the kidneys. This movement into the kidney led to a serious kidney infection. This correlated with kidney infection in about 1% of women, which lead to serious kidney complications.

  • The kidney damage was solely identified in the group of mice that was administered with G. vaginalis group
  • There was some degree of kidney damage among mice that showed the presence of E.coli or G. Vaginalis in the urine
  • Among mice that had both the organisms in the urine, 6% had
    • Severe kidney damage
    • Large numbers of E.coli
    • Indications that E.coli had entered the blood stream, leading to a fatal UTI

G. vaginalis has emerged as a significant contributor to the development of UTI, triggering the E.coli into re-emerging from the reservoirs in the bladder. Therefore, during routine urine examination for UTI, laboratory technicians should also look for the presence of G. vaginalis as a sign of impending UTI.

References :

  1. Clinico-microbiological profile of urinary tract infection in south India – (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3109780/)
  2. What is a Urinary Tract Infection (UTI) in Adults? – (http://www.urologyhealth.org/urologic-conditions/urinary-tract-infections-in-adults)

Source: Medindia

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