From the Journals

New Era? ‘Double Selective’ Antibiotic Spares the Microbiome


 

A new antibiotic uses a never-before-seen mechanism to deliver a direct hit on tough-to-treat infections while leaving beneficial microbes alone. The strategy could lead to a new class of antibiotics that attack dangerous bacteria in a powerful new way, overcoming current drug resistance while sparing the gut microbiome.

“The biggest takeaway is the double-selective component,” said co-lead author Kristen A. Muñoz, PhD, who performed the research as a doctoral student at University of Illinois at Urbana-Champaign (UIUC). “We were able to develop a drug that not only targets problematic pathogens, but because it is selective for these pathogens only, we can spare the good bacteria and preserve the integrity of the microbiome.”

The drug goes after Gram-negative bacteria — pathogens responsible for debilitating and even fatal infections like gastroenteritis, urinary tract infections, pneumonia, sepsis, and cholera. The arsenal of antibiotics against them is old, with no new classes specifically targeting these bacteria coming on the market since 1968.

Many of these bugs have become resistant to one or more antibiotics, with deadly consequences. And antibiotics against them can also wipe out beneficial gut bacteria, allowing serious secondary infections to flare up.

In a study published in Nature, the drug lolamicin knocked out or reduced 130 strains of antibiotic-resistant Gram-negative bacteria in cell cultures. It also successfully treated drug-resistant bloodstream infections and pneumonia in mice while sparing their gut microbiome.

With their microbiomes intact, the mice then fought off secondary infection with Clostridioides difficile (a leading cause of opportunistic and sometimes fatal infections in US health care facilities), while mice treated with other compounds that damaged their microbiome succumbed.

How It Works

Like a well-built medieval castle, Gram-negative bacteria are encased in two protective walls, or membranes. Dr. Muñoz and her team at UIUC set out to breach this defense by finding compounds that hinder the “Lol system,” which ferries lipoproteins between them.

From one compound they constructed lolamicin, which can stop Gram-negative pathogens — with little effect on Gram-negative beneficial bacteria and no effect on Gram-positive bacteria.

“Gram-positive bacteria do not have an outer membrane, so they do not possess the Lol system,” Dr. Muñoz said. “When we compared the sequences of the Lol system in certain Gram-negative pathogens to Gram-negative commensal [beneficial] gut bacteria, we saw that the Lol systems were pretty different.”

Tossing a monkey wrench into the Lol system may be the study’s biggest contribution to future antibiotic development, said Kim Lewis, PhD, professor of Biology and director of Antimicrobial Discovery Center at Northeastern University, Boston, who has discovered several antibiotics now in preclinical research. One, darobactin, targets Gram-negative bugs without affecting the gut microbiome. Another, teixobactin, takes down Gram-positive bacteria without causing drug resistance.

“Lolamicin hits a novel target. I would say that’s the most significant study finding,” said Dr. Lewis, who was not involved in the study. “That is rare. If you look at antibiotics introduced since 1968, they have been modifications of existing antibiotics or, rarely, new chemically but hitting the same proven targets. This one hits something properly new, and [that’s] what I found perhaps the most original and interesting.”

Kirk E. Hevener, PharmD, PhD, associate professor of Pharmaceutical Sciences at the University of Tennessee Health Science Center, Memphis, Tennessee, agreed. (Dr. Hevener also was not involved in the study.) “Lolamicin works by targeting a unique Gram-negative transport system. No currently approved antibacterials work in this way, meaning it potentially represents the first of a new class of antibacterials with narrow-spectrum Gram-negative activity and low gastrointestinal disturbance,” said Dr. Hevener, whose research looks at new antimicrobial drug targets.

The UIUC researchers noted that lolamicin has one drawback: Bacteria frequently developed resistance to it. But in future work, it could be tweaked, combined with other antibiotics, or used as a template for finding other Lol system attackers, they said.

“There is still a good amount of work cut out for us in terms of assessing the clinical translatability of lolamicin, but we are hopeful for the future of this drug,” Dr. Muñoz said.

Pages

Recommended Reading

Typhoid fever bacteria becoming more resistant to antibiotics
MDedge Emergency Medicine
Antibiotic-resistant bacteria emerging in community settings
MDedge Emergency Medicine
Limiting antibiotic overprescription in pandemics: New guidelines
MDedge Emergency Medicine
Multidrug-resistant gram-negative infections treatable with newer antibiotics, but guidance is needed
MDedge Emergency Medicine
Must-read acute care medicine articles from 2022
MDedge Emergency Medicine
FDA broadens warning on potentially contaminated eye products
MDedge Emergency Medicine
Drug-resistant stomach bug infections on the rise: CDC
MDedge Emergency Medicine
Hospital Adverse Events Rise After Private Equity Acquisition
MDedge Emergency Medicine
FDA Approves AI Diagnostic Tool for Early Sepsis Detection
MDedge Emergency Medicine
Automated Risk Assessment Tool Reduces Antibiotic Prescribing Rates
MDedge Emergency Medicine