How antibiotic resistant gut bacteria cause lung infections

Pseudomonas aeruginosa

An Oxford University study has provided the first evidence that antibiotic resistant bacteria can travel from the gut to the lung, increasing the risk of deadly infections. 

The findings coincide with World Antimicrobial Awareness Week and shed light on how antimicrobial resistance (AMR) arises and persists.  

The study, which has been published in Nature Communications highlights the importance of preventing pathogenic bacteria from translocating from the gut to other organs where they can cause serious infections.  

Leading cause of hospital infections

The study was conducted on a patient that carried the bacterium Pseudomonas aeruginosa as part of their gut microbiome. This species is one of the leading causes of infections in hospitals, and one that is particularly good at resisting antibiotics.  

Whilst Pseudomonas is generally not considered to be dangerous when it is embedded in a healthy gut microbiome, it can cause serious infections in the lungs of hospitalised patients. 

During their stay in hospital the patient was treated with the antibiotic Meropenem for a suspected urinary tract infection (UTI). Meropenem treatment caused non-resistant bacteria in the gut and lung to be killed off, and antibiotic resistant mutants of Pseudomonas were able to grow and proliferate.  

Pseudomonas was then found to translocate from the gut to the patient’s lungs during antibiotic treatment, where it evolved even higher levels of antibiotic resistance. 

AMR pathogens in the gut

With AMR being an increasing concern in hospitals, preventing the spread of AMR bacteria to other vital organs such as the lung is critical in vulnerable patients. However, the origin of bacteria that cause these serious infections can be difficult to determine.  

This study shows how the gut microbiome can act as a reservoir of AMR pathogens that can translocate to the lung where they have the potential to cause life-threatening illnesses such as pneumonia.   

The findings of this study suggest that eliminating AMR pathogens from the gut microbiome of hospitalised patients could help to prevent serious infections, and it highlights how antibiotic use can have profound impacts on bacteria that are not actually the target of antibiotic treatment.   

The researchers now intend to assess how frequently gut to lung bacterial translocation occurs in vulnerable patients by collecting samples from a much larger cohort. 

Professor Craig MacLean, Professor at the Department of Biology, Oxford University, said: “Insights such as this are needed in order to develop new interventions to prevent resistant infections. For example, our study highlights a potential benefit of eliminating AMR bacteria like Pseudomonas aeruginosa from the gut microbiome of hospitalized patients, even when these bacteria are not actually causing infection. 

“AMR pathogens can be difficult to eliminate from patients once they have become established, and our work also underscores the importance of avoiding unnecessary antibiotic use, and in developing antibacterial treatments that only target the bacteria that are actually causing an infection.” 

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