In the fight against drug-resistant bacteria, MIT researchers have enlisted the help of beneficial bacterium known as probiotics. In a new study, the researchers showed that by delivering a combination of antibiotic drugs and probiotics, they could eradicate two strains of drug-resistant bacteria that often infect wounds. To achieve this, they encapsulated the probiotic bacterium in a protective shell of alginate, a biocompatible material that prevents the probiotic from being killed by the antibiotic.

"There are so many bacteria now that are resistant to antibiotics, which is a serious problem for human health. "Says Ana Jaklenec, a research scientist at MIT's Koch Institute for Integrative Cancer Research and one of the senior authors of the study.

If you want to be successful in future tests in animals and humans, the probiotic/antibiotic combination could be incorporated into dressings for wounds, where it could help heal infected chronic wounds, they say.

Bacteria wars

The human body contains trillions of bacterial cells, many of which are beneficial. In some cases, these bacteria help fend off infection by secreting antimicrobial peptides and other compounds that kill pathogenic strains of bacteria. Others outcompete harmful strains by taking up nutrients and other critical resources.

Scientists have previously tested the idea of applying probiotics to chronic wounds, and they've had some success in studies of patients with burns, Li says. However, the probiotic strains usually can not combat all of the bacteria that would be found in an infected wound. Combining these strains with traditional antibiotics would help to kill more of the pathogenic bacteria, but the antibiotic would likely kill off the probiotic bacteria.

Probiotic bacteria

The MIT team devised a way to get around this problem by encapsulating the probiotic bacteria so that they would not be affected by the antibiotic. They chose alginate in part because itis already used in dressings for chronic wounds, where it helps to absorb secretions and keep the wounddry. Additionally, the researchers also found that alginate is a component of the biofilms that clusters of bacteria form to protect themselves from antibiotics.

For this study, the researchers chose to encapsulate the type of commercially available probiotic known as Bio-K +, which consist of three strains of  Lactobacillus  bacteria. These strains are known to kill  methicillin-resistant Staphylococcus aureus  ( MRSA ). The exact mechanism by which they are not known, but one possibility is that the pathogens are susceptible to the lactic acid produced by the probiotics. Another antimicrobial peptides or other proteins that kill the pathogens or disrupt their ability to form biofilms.

The researchers delivered the encapsulated probiotics along with an antibiotic called tobramycin, which they chose among other tested MRSA  and Pseudomonas aeruginosa growing in a lab dish

Better wound healing

The envision that this approach could be used to develop new types of bands or other wound dressings embedded with antibiotics and alginate-encapsulated probiotics. Before that can happen, they plan to further test the approach in animals and possibly in humans.

"The good thing about alginate is it's FDA-approved, and the probiotic we use is approved as well," Li says. "I think probiotics can be something that may revolutionize wound treatment in the future." With our work, we have expanded the application of probiotics. "