OCT 15, 2018 6:18 PM PDT

Surprising Source of Hospital-acquired Infections is Found

WRITTEN BY: Carmen Leitch

Hospitals are supposed to be a place where people get well, but unfortunately, many people that stay in the hospital for more than a few days end up with an infection. A lot of those patients are transplant recipients with compromised immune systems. While one might suspect that the infectious germs are coming from a dirty hospital room, other sick patients, or a coughing visitor, researchers at Stanford University found that the most common source of a hospital patient’s bloodstream infection is the that patient’s own gut.

The researchers utilized powerful bioinformatic tools to identify the source of hospital-acquired infections. Tracing them accurately, instead of making educated guesses, will help to address the factors causing the infections effectively, said Ami Bhatt, MD, Ph.D., assistant professor of hematology and genetics. The findings have been reported in Nature Medicine.

“Until now, we couldn’t pinpoint those sources with high confidence,” said Bhatt, who is the senior author of the study. “That’s a problem because when a patient has a bloodstream infection, it’s not enough simply to administer broad-spectrum antibiotics. You need to treat the source, or the infection will come back.”

The free computational tool created for this work, called StrainSifter, may help clinicians figure out whether an infectious pathogen is coming from a skin wound, from gut microbes leaking into the bloodstream, or from an inserted medical device like a catheter, explained Bhatt. That information can help eradicate the infection faster. 

We already know that many microbes that live in the gut cause no harm to us, as long as they stay there; if some of them end up elsewhere they can be very harmful. Thus, the researchers began their study there.

“Often, these bugs aren’t intrinsically pathogenic,” Bhatt said. “They’re perfectly well-behaved in the gut. It’s only when they show up in the wrong place -- due, for example, to leaking through a disrupted intestinal barrier into the bloodstream -- that they cause trouble.”

The research team collected blood and stool samples from thirty patients that had blood infections after a bone-marrow transplant procedure. They wanted to know if the pathogenic bacterial strain in an individual's blood could also be found in the same patient’s stool sample, which was taken prior to surgery.

Huge amounts of genetic data had to be analyzed for this work, something only possible since the huge advances in genomics in recent decades. The scientists had to confirm that it wasn’t just the same kind of bacterium; it had to be the exact same strain.

“Just finding E. coli in a patient’s blood and again in that patient’s stool doesn’t mean they’re the same strain,” Bhatt noted. 

The researchers also looked at the microbial landscape in each of the patients and confirmed that the infectious pathogen from each individual matched a strain in their gut. They also knew from their extensive study that none of the bugs they found in a patient’s bloodstream were present in a different patient’s stool or blood samples. 

“Because the gut normally harbors more than 1,000 different bacterial strains, it’s looked upon as a likely culprit of bloodstream infections, especially when the identified pathogen is one known to thrive inside the gut,” Bhatt said. “But while this culpability has been assumed — and it’s an entirely reasonable assumption — it’s never been proven. Our study demonstrates that it’s true.”

“I don’t think we’re passing around active infections among one another as often as has been assumed,” added Bhatt. “Our results suggest that people are the most likely source of their own infections. Maybe we need to get rid of this idea of catching others’ infections, and give more thought to the health of our own resident microbial ecosystems.”


Sources: Stanford Medicine, Biology of Blood and Marrow Transplantation, Nature Medicine

About the Author
  • Experienced research scientist and technical expert with authorships on 28 peer-reviewed publications, traveler to over 60 countries, published photographer and internationally-exhibited painter, volunteer trained in disaster-response, CPR and DV counseling.
You May Also Like
MAY 11, 2020
Cell & Molecular Biology
3D Cell Culture Model Suggests Herpes Can Cause Alzheimer's
MAY 11, 2020
3D Cell Culture Model Suggests Herpes Can Cause Alzheimer's
Alzheimer's is a common form of dementia that affects as many as 5.5 million Americans and the incidence is increasing a ...
MAY 14, 2020
Microbiology
Cats Can Get Infected by SARS-CoV-2 and Transmit It to Other Cats
MAY 14, 2020
Cats Can Get Infected by SARS-CoV-2 and Transmit It to Other Cats
New research reported in the New England Journal of Medicine has indicated that domestic cats can easily be infected wit ...
MAY 17, 2020
Microbiology
More Research Links ALS to the Microbiome
MAY 17, 2020
More Research Links ALS to the Microbiome
The community of microorganisms that lives in the gastrointestinal tract has a powerful influence on human health.
JUN 21, 2020
Microbiology
Poor Oral Hygiene May Worsen Gut Inflammation
JUN 21, 2020
Poor Oral Hygiene May Worsen Gut Inflammation
Good dental hygiene benefits more than just the teeth and gums; researchers have found that poor oral health can contrib ...
JUL 05, 2020
Cell & Molecular Biology
COVID-19 Attacks Endothelial Cells
JUL 05, 2020
COVID-19 Attacks Endothelial Cells
The pandemic virus SARS-CoV-2 enters the body through the respiratory system to cause the illness COVID-19. But we know ...
JUL 22, 2020
Microbiology
Tiny, Parasitic Bacteria Can Find a Home in the Human Mouth
JUL 22, 2020
Tiny, Parasitic Bacteria Can Find a Home in the Human Mouth
Some microbes that live in environments as diverse as groundwater and moose have also been found in the human mouth.
Loading Comments...