Decreased bladder microbiome diversity associated with urinary tract infections

 A catheter

A catheter

Urinary tract infection is one of the top healthcare-associated infections along with pneumonia and gastrointestinal illness, according to the Centers for Disease Control and Prevention. In nursing homes, UTIs are the most common type of infection and are often caused by catheters. Catheters are used to collect urine in both male and female patients. Older patients tend to need catheters for a longer period of time, putting them at higher risk for infections as it allows for the greater colonization of infectious bacteria. In an article published in the Journal of Infection, researchers in Houston, Texas experimented with a catheter coated in a specific strain of Escherichia coli to see if it would prevent catheter-associated urinary tract infections (CAUTIs) in older patients.

Eight men and two women, with a mean age of 70.9, were enrolled in the study. All but one subject received antibiotics prior to the insertion of the catheter. This antibiotic regime most likely caused a significant disruption to the existing microbial balance in the bladder. Despite the antibiotic use, the subjects’ urine still showed the presence of microorganisms after antibiotic treatment and immediately prior to catheter insertion. The study catheters that each patient received were previously colonized in the lab by E. coli strain HU2117, which is a strain that is missing an essential infection-allowing gene. By using the benign strain without this papG gene, the patients were safe from any harm. The hypothesis was that this E. coli strain would be delivered to the bladder and compete with infectious bacteria, not allowing the pathogens to colonize the bladder.

Urine samples were collected from the subjects on days 0, 1, 3, 7, 14, 21, and 28 after catheter insertion. After that, samples were collected monthly until no E. coli was detected. Three of the subjects suffered from febrile UTI, and two from urosepsis/bacteremia, another form of UTI. In these five subjects E. coli was not the predominant bacteria and was not even detected during infection in some cases. From the results of this study we can conclude that E. coli HU2117 is most-likely not effective enough in preventing other pathogenic bacteria from infecting the bladder.  

The researchers explain that the reason why their experiment had a negative result was that the E. coli did not increase bacterial diversity in the bladder. Diversity in colonization is usually what protects from infection and in this study, decreased diversity led to UTIs. This is a theme we have seen over and over again on the blog. Further informative studies could include those that help us understand the healthy and diverse microbiome of the bladder, and subsequently use that information to decrease UTI occurrence.  

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