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 P. aeruginosa were able to grow and proliferate.
P. aeruginosa 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.
The findings of this study suggest that eliminating AMR pathogens from the gut microbiome of hospitalized 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.
Researchers tested the patient throughout their time in hospital to track the duration of their infection with P. aeruginosa. They used a genetic approach, creating a time-calibrated bacterial family tree that allowed them to analyse the progression and location of infection, plus its evolution. They also found high genetic diversity in the gut, which also suggests that the microbiome may be a reservoir for AMR to arise.
Fortunately, the patient in this case had an immune response to the AMR bacteria in their lungs, preventing the infection from causing pneumonia. However, many people in critical conditions, particularly over winter, have a weakened immune system, meaning the body is less able to fight off disease. AMR policies often focus on reducing infection from external sources, but understanding how AMR can develop and spread within a patient is just as vital.
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.