Antibiotics wreak havoc on the gut. Can we kill the bad bugs and spare the good ones?

Inside every human is a thriving zoo of bacteria, fungi, viruses and other microscopic organisms collectively known as the microbiome. Trillions of microbes live in the digestive tract alone, a menagerie estimated to contain more than 1,000 species.

This ecosystem of tiny stuff affects our health in ways science is only beginning to understand, facilitating digestion, metabolism, the immune response and more. But when serious infection sets in, the most powerful antibiotics take a merciless approach, wiping out colonies of beneficial bacteria in the digestive tract and often prompting secondary health problems.

"Increasingly, researchers are recognizing the benefits of protecting