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Own bacteria may cause some infections in hospitals: Study

If you are in a hospital, then at times, you get bacterial infections from one source — yourself.

HQ Team

January 12, 2023: If you are in a hospital, then at times, you get bacterial infections from one source — yourself.

Researchers at the Washington University School of Medicine in St. Louis suggest screening patients for hidden reservoirs of dangerous bacteria could supplement infection-control efforts and help prevent deadly infections.

The researchers found evidence pointing to an unexpected source of such bacteria: the hospitalized patients.

Nearly 100,000 people die yearly in US hospitals of infections they develop after admission. 

Despite intense infection-control efforts, new strains of bacteria keep emerging, seemingly out of nowhere, to sicken people in hospitals worldwide.

Mice study

After studying mice, the researchers discovered that urinary tract infections (UTIs) could arise after sterile tubes, called catheters, are inserted into the urinary tract, even when no bacteria are detectable in the bladder beforehand.

The researchers studied mice with UTIs caused by A. baumannii. They used mice with weakened immune systems because, like people, healthy mice can fight off A. baumannii.

Once the infections had resolved, and the mice got cured for two months, the researchers inserted catheters into the mice’s urinary tracts with a sterile technique. 

Within 24 hours, about half of the mice developed UTIs caused by the same strain of A. baumannii as the initial infection.

The catheters are used in hospitals to empty the bladders of people undergoing surgery. In the mice, inserting the tubes activated dormant Acinetobacter baumannii (A. baumannii) bacteria hidden in bladder cells, triggering them to emerge, multiply and cause UTIs.

“You could sterilize the whole hospital, and you would still have new strains of A. baumannii popping up,” said co-senior author Mario Feldman, a professor of molecular microbiology. 

Cleaning not enough

“Cleaning is just not enough, and nobody knows why. This study shows that patients may be unwittingly carrying the bacteria into the hospital, which has implications for infection control.” 

Suppose someone has a planned surgery and is going to be catheterized. In that case, doctors must determine whether the patient is carrying the bacteria and cure that person of it before the surgery.

“Ideally, that would reduce the chances of developing one of these life-threatening infections” for vulnerable patients already hospitalized with serious illnesses, he said. 

Baumannii, the opportunistic bacteria, is a significant threat to hospitalized people, causing many cases of UTIs in people with urinary catheters, pneumonia in people on ventilators, and bloodstream infections in people with central-line catheters in their veins. 


The bacteria are resistant to a broad range of antibiotics, so such infections are challenging to treat and can quickly turn deadly.

Most UTIs among healthy people is caused by the bacterium Escherichia coli (E. coli).

Research has shown that E. coli can hide out in bladder cells for months after a UTI seems to have been cured and then re-emerge to cause another infection.

“The (A. baumannii) bacteria must have been there all along, hiding inside bladder cells until the catheter was introduced,” said co-senior author Scott J. Hultgren.

“Catheterization induces inflammation, causes the reservoir to activate, and the infection blooms.”

Since A. baumannii rarely causes symptoms in otherwise healthy people, so many people who carry the bacteria may never know they’re infected.

Walking around with bacteria

“I wouldn’t put much weight on the precise percentage, but I think we can say with certainty that some percentage of the population is walking around with A. baumannii,” Feldman said.

“As long as they’re healthy, it doesn’t cause any problems, but once they’re hospitalized, it’s a different matter. This changes how we think about infection control. 

“We can start considering how to check if patients already have Acinetobacter before they receive certain types of treatment; how we can get rid of it; and if other bacteria that cause deadly outbreaks in hospitals, such as Klebsiella, hide in the body in the same way. That’s what we’re working on figuring out now.”

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