We're currently locked in an arms race against bacteria, and the bugs are winning as they continue to evolve resistance to our best drugs. Luckily, we have some double agents in the war – probiotics, or "good" bacteria that help keep bad bugs at bay. And now, MIT researchers have found a way to combine probiotics and antibiotic drugs into an uneasy alliance that seems to work better than either treatment alone.

As important as antibiotics have been for medicine over the past century, relying too heavily on them is proving to be dangerous. Overuse is speeding up the natural evolution process to the point where even our last line of defense is beginning to fail, threatening to return us to "the dark ages of medicine" where routine procedures and illnesses become potentially deadly again.

Although new antibiotics and alternative treatments are in development, there are still ways to squeeze more use out of existing technology, like supercharging old antibiotics or combining "failed" ones. In this case, the MIT team took a commercially-available probiotic called Bio-K+ and combined it with a regularly-used antibiotic called tobramycin.

Each of these ingredients is effective against a different superbug. Bio-K+ contains three species of Lactobacillus bacteria, often found in yogurt, which is able to kill a particularly nasty bug called methicillin-resistant Staphylococcus aureus (MRSA). Researchers aren't sure exactly how the probiotic kills MRSA, but it might have something to do with the lactic acid, peptides or other proteins they produce.

Meanwhile, tobramycin was chosen because it's effective against Pseudomonas aeruginosa. These two bacteria species often occur together in wound infections, meaning applying either Bio-K+ or tobramycin alone isn't usually enough to clear out everything.

The problem, of course, is that the antibiotic would also kill the probiotic. To overcome that, the researchers encapsulated the Bio-K+ in a compound called alginate, which forms part of the biofilm that colonies of bacteria build to protect themselves. As a bonus, alginate is already often used in wound dressings.

To test the unlikely duo, the MIT team added the mix to a lab dish containing Pseudomonas and MRSA, and found that it completely eradicated all bacteria. When they didn't bother wrapping the Bio-K+ in alginate, the antibiotic killed the probiotic as expected, which in turn meant the MRSA survived the attack.

"When we just used one component, either antibiotics or probiotics, they couldn't eradicate all the pathogens," says Zhihao Li, lead author of the study. "That's something which can be very important in clinical settings where you have wounds with different bacteria, and antibiotics are not enough to kill all the bacteria."

The researchers say the next step is to test the combo in animals and humans. After that, the treatment could be put to work in bandages that can help fight these kinds of infections in wounds. Alginate and the probiotic are already FDA-approved for human use, so that's one less hurdle in the way.

The research was published in the journal Advanced Materials.

Source: MIT

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