Friendly bacteria thriving in the gut of healthy humans show antimicrobial resistance, an ability that makes them resist the harmful effects of antibiotics, a new study reveals. Such resistance is due to the presence of antimicrobial-resistant genes in their genomes that can spread even to pathogens, the study says1.

These findings will be useful for clinicians to revise treatment options such as antimicrobial therapies for patients undergoing surgery and organ transplantation.

Friendly gut bacteria are frequently exposed to several antimicrobials, designed to kill pathogens whose drug-resistance trait is a well-known fact. However, little is known about the drug-resistance aspect of the resident gut bacteria.

Scientists from the Translational Health Science and Technology Institute in Haryana and All Indian Institute of Medical Sciences in New Delhi, India, led by Bhabatosh Das, sequenced the genomes of five dominant gut bacterial species isolated from the faecal samples of healthy individuals. They then analysed their responses to 28 different antibiotics.

The dominant bacteria were found to harbour 25 antimicrobial-resistant genes that made them multi-drug resistant. They showed resistance to at least nine different antibiotics. The genes responsible for the resistance to antibiotic tetracycline were the most abundant and diverse.

The researchers then found that the bacteria that thrive in the intestines and cause cholera were able to pick up antimicrobial-resistant genes from the pool of friendly gut bacteria.

The insights gleaned from this study will help track the possible reservoirs of resistant genes for the bacterial pathogens, says Das.