The movement of hospital-acquired bacteria from the lungs to the intestines increases the risk of sepsis

The movement of hospital-acquired bacteria from the lungs to the intestines increases the risk of sepsis

A hospital-acquired bacteria that causes serious infections can travel from the lungs to the intestines in the same patient, increasing the risk of life-threatening sepsis, new research shows.

Published today (November 25th) inNatureResearchers at the Wellcome Sanger Institute analyzed DNA data from hospital patients to understand the movement of the bacterium.Pseudomonas aeruginosa(P. aeruginosa)within individuals.

The research sheds light on how lung infections can lead to the spread of a key disease-causing bacteria between multiple parts of the body, increasing the risk of sepsis in at-risk patients. Findings from the study could inform future strategies for hospitals to track and prevent sepsis-related deaths.

P. aeruginosais a common bacterium that can cause disease in humans, plants and animals. It is a leading cause of hospital-acquired infections and can lead to conditions such as pneumonia, ear infections, urinary tract infections and wound infections.

The bacteria is also known to be a cause of sepsis. Sepsis occurs when the body does not respond properly to an infection. The infection-fighting process begins to attack the body, causing some organs to fail. It is a life-threatening condition and there are 48,000 sepsis-related deaths in the UK every year and five deaths occur every hour.

A previous study has already shown thisP. aeruginosahas passed from the intestines to the lungs of a single intensive care patient, revealing its ability to move and colonize other parts of the body. However, how often this happens and in which direction the bacteria spread is still unclear.

In a new study, researchers at the Sanger Institute analyzed metagenomic sequencing data from 256 hospitalized patients in Italy. They used this data to understand whereP. aeruginosabegins to colonize and in which direction the bacterium moves through the body.

Of the 84 patients whereP. aeruginosaAlthough genomes could be restored, the team found 27 cases in which the same bacterial clone (cells that are identical in their DNA) appeared in multiple parts of the body. This indicates that most of these infections were not transmitted repeatedly in the hospital environment, but rather were established and colonized by a single clone over time and spread within the patient's own body. Additionally,P. aeruginosaInfections were significantly more common in intensive care patients than in patients in other wards.

By creating family trees ofP. aeruginosaThe team predicted that most of the strains that spread originated in the lungs. This suggests that infections most likely travel from the lungs to the intestines, whereP. aeruginosacan establish long-term colonizations. The researchers suggest that naturally swallowing sputum – a mixture of saliva and mucus from the lungs – may contain themP. aeruginosacould be a likely route of intestinal colonization. They weren't found eitherP. aeruginosaonly in nasal samples, suggesting that it must first be present elsewhere in the body and the nose acts as an overflow site rather than a stable colony site.

The researchers also found common DNA changes in genes associated with antibiotic resistance (AMR), regardless of where the bacteria are located in the body. These DNA changes make treatment much more difficult.

Ultimately, the results have significantly expanded a small body of existing knowledge about the movement of a dangerous bug within a person. Colonization ofP. aeruginosain the lungs should therefore be considered a risk factor for sepsis that begins in the intestines in patients who are particularly susceptible to this life-threatening disease.

Dr. Lewis Fisher, lead author at the Wellcome Sanger Institute, said: "We found that most patients carried the same strain of the pathogen."P. aeruginosaSeveral samples show that once this bacterium has become established, it tends to persist rather than being replaced by new infections. This persistence helps explain why it can be so difficult to eradicate the virus in hospitals.”

Dr. Ron Daniels, founder and chief medical officer of the UK Sepsis Trust, said: "Pseudomonas infections are notoriously difficult to eradicate and are a major problem in our intensive care units, particularly in immunocompromised patients, and are a leading cause of sepsis. This new research serves to improve our understanding of this organism, which can only be good for our patients now and in the future - it shows how little we know about disease-causing pathogens and their behavior."

We also saw rapid genetic changes in antibiotic resistance genes, regardless of where the bacterium was found in the body. This highlights how quicklyP. aeruginosacan adapt, making treatment and control in the intensive care unit increasingly difficult.”

Professor Jukka Corander, co-author at the Wellcome Sanger Institute and the University of Oslo, Norway

Dr. Josie Bryant, senior author at the Wellcome Sanger Institute, said: "Our findings show that these bacterial infections often spread within patients' own bodies, typically from the lungs to the intestines. Detecting this hidden movement is key to improving the way hospitals monitor and prevent sepsis in vulnerable patients."

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