Antibiotic-resistant bacteria know how to avoid medicines


Bacteria are known to move within the human body using pathways that we know little about. A recent hospital case in Spain suggests that antibiotic-resistant bacteria can even change their route, migrating from the gut to the lungs and back again.


The patient was admitted to an intensive care unit following an epileptic seizure. Since his first day in hospital, the man’s lungs had shown the presence of a bacterium called Pseudomonas aeruginosa, which causes a common infection in the lungs, urinary tract and intestines. For 39 days, he was mechanically ventilated while doctors used antibiotics to fight the infection in his lower airways.

On day 12, the patient developed a urinary tract infection, which the doctors treated with another antibiotic, meropenem . Shortly after the end of treatment,  P. aeruginosa was found in both the gut and lungs, which, according to the authors, provides “strong evidence for gut-to-lung transmission ” – and possibly also vice versa.” Fortunately, the man’s immune system kicked in and he was discharged after more than a month in the hospital. But it could have been much worse.

By studying the genetic diversity of all the bacteria collected from the patient during their ICU stay, the researchers found evidence that the infection likely started in the gut about three weeks before the hospital visit. By the 24th day of the ICU stay, the infection had begun to evolve and re -settled in the patient’s lungs.


“The presence of these bacteria in the lung and gut implies that meropenem resistance either evolved in the gut before being transmitted to the lung, or that this lineage passed secondarily from lung to gut after developing resistance to the meropenem in the lung,” write the authors. If an intestinal infection is able to migrate to the lungs, carrying antibiotic resistance with it, then this could be an important route of infection that doctors need to consider.


“In this case, resistance was driven by the spread of independent bacteria in the gut and lung that adapted to local differences in antibiotic concentration,” the authors write.

The patient in Spain showed the presence of P. aeruginosa in the intestine soon after starting a treatment with meropenem. Perhaps, the authors suggest, the antibiotic treatment facilitated this gut-to-lung transmission, killing off the competing bacteria that usually keep the infection in check, for example.

  • Gut to lung translocation and antibiotic mediated selection shape the dynamics of Pseudomonas aeruginosa in an ICU patient. (


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