Antibiotic resistance presents a growing threat to global health, causing 23,000 deaths each year in the United States, according to the Centers for Disease Control and Prevention. As the scientific community searches for alternatives to antibiotics, researchers are exploring how they can replicate the ability of mucus to naturally control pathogenic bacteria, with the help of some familiar oral pathogens and potentially preventing dental caries too.
“My lab and others around the world have begun to engineer mucin-inspired polymers and [synthetic] mucus,” said Katharina Ribbeck, PhD, professor of tissue engineering at the Massachusetts Institute of Technology. “We want to use these engineered polymers to control problematic pathogens inside and outside of the body and to stop the growing threat of antibiotic-resistant microbes.”
The human body produces about a gallon of mucus each day to sustain a protective coating on more than 2,000 square feet of internal surface area, including the digestive tract, mouth, eyes, lungs, female reproductive tract, and nose. Most of the trillions of microbes inhabiting the body live inside the mucus that lines the digestive tract. Ribbeck has been researching how mucus maintains a healthy balance between beneficial and potentially harmful microbes.
“Over millions of years, the mucus has evolved the ability to keep a number of these problematic pathogenic microbes in check, preventing them from causing damage,” said Ribbeck. “But the mucus does not kill the microbes. Instead, it tames them.”
Ribbeck’s team has investigated how mucins, the sugar-coated molecules that form the mucus gel, influence the makeup of the body’s internal microbial communities by constraining the formation of multicellular assemblies (also known as biofilms) by the microbes. As a case study, the researchers looked at the mucins found in saliva, called MUC5B.
Next, they grew 2 types of bacteria known to compete in the mouth: Streptococcus mutans, which forms cavities, and Streptococcus sanguinis, a bacterium associated with healthy oral conditions. They found that S mutans quickly outgrew S sanguinis when grown together outside of saliva or mucin-containing media. But grown in the presence of MUC5B (both in real saliva and in MUC5B-containing synthetic mucus), the 2 species tended to establish a more even balance, suggesting that mucin could be instrumental in supporting greater bacterial diversity.
“We conclude from these findings that MUC5B may help prevent diseases such as dental caries by reducing the potential that a single harmful species will dominate,” said Ribbeck, who plans to continue to investigate the potential role of mucins in maintaining microbial diversity in other mucosal surfaces throughout the body.