A diarrhoea-causing bacterium does its dirty work by emitting a compound that harms certain bacteria residing in the human gut.
The bacterium Clostridium difficile is the leading cause of diarrhoea in people who have been taking antibiotics, which upset the gut’s natural microbial balance. Lisa Dawson at the London School of Hygiene and Tropical Medicine and her colleagues examined the effects of para-cresol, a compound made by C. difficile, on microbes growing in lab dishes. They found that the compound blocks the growth of many species of gut bacterium but leaves C. difficile itself relatively unscathed.
The team dosed mice with antibiotics and then infected the rodents with C. difficile. Numerous species of gut bacterium struggled to grow in mice infected with ordinary C. difficile. But those same bacteria thrived in mice infected with mutant C. difficile that does not make para-cresol, suggesting that the compound gives the pathogen a survival edge.