 red color that can be detected by analyzing stool samples. This process now takes several hours, but the researchers hope to shorten that time.
The researchers had hoped to further engineer L. lactis so that it could treat or prevent cholera infections. They began by engineering the microbes to produce antimicrobial peptides that could kill V. cholerae, but they eventually found that the peptides were being rendered harmless after being secreted by the cells.
Serendipitously, however, the team discovered that unmodified L. lactis can actually kill cholera microbes by producing lactic acid, a natural byproduct of their metabolism. Lactic acid makes the gastrointestinal environment more acidic, inhibiting the growth of V. cholerae.
The engineered version of L. lactis does not produce enough lactic acid to kill cholera microbes, so the researchers combined the engineered bacteria with the unmodified version to create a probiotic mixture that can both detect and treat cholera. In tests in mice, the researchers found that this probiotic mixture could successfully prevent cholera infections from developing and could also treat existing infections.
Alternatives to antibiotics
Collins says he anticipates that the probiotic, which could be incorporated into a pill or a yogurt-like drink, could be used either as a preventative measure or for treating infections once they begin. Having the ability to diagnose cholera easily could also help public health officials detect outbreaks earlier and monitor the spread of the disease.
The researchers are now exploring the possibility of using this approach to combat other microbes, such as Clostridium difficile, which causes gastrointestinal infections, and bacteria known as enterococci, which can cause many types of infections.
"There is emerging interest in using probiotics to treat disease, largely from the growing recognition of the microbiome and the role it plays in health and disease, and the pressing need to find alternatives to antibiotics," Collins says.
The research was funded by the Defense Threat Reduction Agency, the Gates Foundation, and the Paul G. Allen Frontiers Group.