Scientists discover antibiotic that spares 'good' bacteria

One of the biggest downsides of antibiotic use is the way they indiscriminately kill both "good" and "bad" bacteria.

A single course of treatment with this life-saving drug can not only destroy the disease-causing invaders in the human body, but also have a "huge" impact on the gut and its resident collection of microbes.

This impact can sometimes lead to an overgrowth of certain bacteria or fungi. For example, women are up to 30% likely to develop a yeast infection after antibiotic treatment.

Scientists at the University of Illinois at Urbana-Champaign are working on a solution. They have discovered a new antibiotic called Lolamycin that can tackle gram-negative pathogens while leaving other microbes alone, Science Alert reports.

There's still a long way to go before the drug can be tested on humans, but researchers hope it could serve as a model for future antibiotic development.

Gram-negative bacteria are common infectious agents in the gut, lungs, bladder and blood and are notoriously difficult to kill. Their resistance to current antibiotics is one of the most urgent threats facing human health worldwide today.

Broad-spectrum antibiotics can kill both gram-negative and gram-positive bacteria. But scientists say there is an urgent need to find a drug that specifically targets gram-negative bacteria, as they are more likely to be resistant to our current antibiotics. This gives more microbes that are beneficial to human health a chance to be spared.

A drug like Lolamycin can be just that. In lab dishes, when lolamycin is pitted against 130 drug-resistant strains of common gram-negative bacteria, such as E. coli, K. pneumoniae and E. cloacae, the drug killed every one of them, succeeding where many other antibiotics fail.

In live rodents, Lolamycin also successfully treats acute pneumonia and bloodstream infections by sparing the gut microbiome.

In fact, the scientists found that the drug "had no effect on gram-positive bacteria or nonpathogenic gram-negative commensal bacteria" that live in the mice.

This is an exciting discovery, given that even a short course of antibiotic treatment can lead to a rapid reduction in the diversity of the types of microbes living in the human gut, and this can last for months before returning to normal.

The health implications of these changes are not well understood, but they seem to leave the patient open to secondary infections after the use of certain antibiotics.

Lolamycin is different. Unlike amoxicillin (a broad-spectrum antibiotic) or clindamycin (an antibiotic that is only gram-positive), this new drug "did not induce any significant changes" in the gut microbiome of mice for about a month after treatment.

During that time, the mice that were treated with lolamycin were exposed to a bacterial infection that often develops in the colon after antibiotic use: clostridioides difficile.

Mice treated with lolamycin did not develop infections caused by C. difficile to nearly the same extent as those treated with clindamycin or amoxicillin.

Considering that about 500,000 infections with C. difficile infections, 30,000 of which are fatal, the development of a microorganism-sparing antibiotic could be lifesaving.

Scientists are now working to refine their work to ensure that pathogens do not become resistant to lolamycin over time.

"The gut microbiome is essential for maintaining host health, and disrupting it can lead to many harmful consequences, including infection with C. difficile and others," the authors conclude.

"Therefore, pathogen-specific antibiotics such as lolamycin will be critical to minimize collateral damage to the gut microbiome; this microbiome-sparing effect would make such antibiotics better for patients compared with antibiotics in current clinical practice." | BGNES