Predatory Bacteria Can Cannibalize Drug-Resistant Bugs

A new study shows that a strain of bacteria was able to kill pneumonia inside the lungs of sick rats.

Antimicrobial resistance is one of the greatest public health threats of our time, with more than 700,000 people dying each year from drug-resistant strains of TB, malaria and HIV/AIDS. Without new methods of killing these fast-mutating microbes, an estimated 50 million people a year could die from drug-resistant infections by 2050.

"Without effective antibiotics, we'll be thrust back into the mid-1800s," Robert J. Mitchell, a microbiology professor and researcher at the Ulsan National Institute of Science and Technology in Korea, told Seeker. Mitchell is one of a handful of global scientists studying a unique strain of "predatory bacteria" that could hunt down and kill drug-resistant bugs inside a patient's body.

According to a new paper, these so-called "vampire" bacteria - named for their nasty habit of latching on to other microbes and sucking out their innards - have successfully hunted down and killed pneumonia inside the lungs of sick rats. The paper, authored by Daniel Kadouri of the Rutgers Medical School, presents compelling new evidence that vampire bacteria could become a viable weapon against the rising threat of superbugs.

Predatory bacteria were first identified in 1962 as fast-swimming bacteria that attack and eat other bacteria. They're found everywhere in the natural environment, in soils, oceans, rivers, lakes, and are even present in the human gut. The favorite strain of predator bacteria among researchers like Mitchell and Kadouri are called Bdellovibrio-and-like-organisms (BALOS).

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"These bacteria are able to penetrate the double membrane of Gram-negative bacteria, enter into the prey and consume it from the inside out," says Mitchell. After sucking down a tasty meal, the BALOS use the energy boost to multiply. "A predator can produce anything from two to seven progeny from a single prey.

Scientists don't know enough about predatory bacteria to "program" the hungry suckers to target specific microbes. The best current technique, Mitchell explains, is to identify naturally occurring predators that have a "taste" for certain kinds of diseases. Once the predator bacteria are isolated in culture, researchers must feed them daily to keep them alive and reproducing. Then it's time to set them loose on disease pathogens.

Kadouri's rat experiments were the first ever to employ therapeutic predatory bacteria in living mammals. Before that it was just fish and chickens. The dream is to one day test these disease-hunting bacteria in humans. Earlier this year, both Mitchell and Kadouri proved in separate studies that BALOS pose no threat to healthy human cells in culture. Testing on real people is still years away.

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"One of the biggest obstacles to human trials, other than federal approval, is psychological," says Mitchell, "It's the whole idea of telling a patient, 'Hey, we're going to get rid of your pathogenic bacteria by feeding you bacteria.'"

Another big unknown is the long-term effect of these predatory bacteria inside the body. Will they establish themselves and become part of the body's microbial mix? And is that a bad thing or a good thing? Mitchell and his colleagues are chasing down these answers, thanks in part to grants from DARPA's Pathogen Predators program.

In the meantime, the global health community is on high alert. In September, the United Nations held its first-ever general assembly dedicated exclusively to antimicrobial resistance. Addressing the assembly, the World Health Organization's director general, Margaret Chan, warned that a lack of new treatment options could soon give rise to a terrifying post-antibiotic era.

"Doctors facing patients will have to say, 'I'm sorry - there's nothing I can do for you.'"