Bacteria are becoming resistant to antibiotics far more quickly than humans are discovering new ones. That's why a DARPA-funded research team is exploring a fascinating new way we might win the war against germs: not with drugs, but with predatory bacteria that sound like monsters from science fiction.
Lions, sharks and Schwarzenegger flicks are more likely to come to mind when you hear the word "predator", but certain bacteria are also fearsome hunters, voraciously consuming their fellow single-celled organisms. In fact, predatory bacteria have no trouble annihilating some of the most drug-resistant bugs. Microbiologist Daniel Kadouri hopes we can use these killers to our advantage.
"Every agency out there — the WHO, the CDC, the NIH — have all figured out that drug resistant pathogens are as big a threat as global warming," Kadouri said when I spoke with him at a DARPA technology expo this week. "We're trying to see if we can do things differently, by using predatory bacteria as live antibiotics."
For the past few years, Kadouri and his colleagues have been conducting laboratory experiments that pit two specific predators — bacteria from the genera Bdellovibrio and Micavibrio — against some of the deadliest human pathogens.
"Bdellovibrio attacks biofilms," Kadouri said, referring to the sticky bacterial secretions that become the spawning ground of drug-resistant infections. "They will attach to the biofilm, drill themselves inside the cells, and start dividing. From one [Bdellovibrio] cell entering you can get about 80 cells breaking out. It's like something from the movie Alien."
Scanning electron micrograph of Bdellovibri bacteriovorus drilling into an E.coli biofilm. Image: Daniel Kadouri
Micavibrio uses a totally different but equally horrifying mode of attack, attaching itself to the outside of its prey like a vampire. "Basically, they suck other bacteria dry," Kadouri said.
Kadouri's research has shown that each of these micro-monsters can attack a wide range of disease organisms, including Pseudomonas, which causes wound infections, and Vibrio cholerae, the little varmint behind cholera. And a bug that's resistant to antibiotics is no big deal. "Becoming drug resistant doesn't interfere with their attack because it's a totally different pathway," Kadouri explained.
At this point, you might be wondering whether swallowing a pill filled with one of nature's most efficient killing machines might have some, erm, unfortunate side-effects on the host. Kadouri and his colleagues have considered this possibility too, which is why they have just completed a battery of studies testing Bdellovibrio and Micavibrio in live animals and human cell lines. "They're completely benign," Kadouri said, explaining that in no experiments did either predatory bacteria have a harmful effect on animal tissue.
Scanning electron micrograph of Micavibrio aeruginosavorus preying on Pseudomonas aeruginosa, an opportunistic human pathogen. Image: Daniel Kadouri
There's still the possibility that an over-zealous predator might wreak havoc on our native gut flora. While preliminary research suggests that Bdellovibrio and Micavibrio tend to leave our friendlies alone, it's a possibility that researchers are continuing to investigate. Antibiotics can definitely wreak havoc on our microbiomes, however, so if predatory bacteria are less harmful in this respect, that's a major selling point.
It will be years before doctors are prescribing live bacteria to combat infections — Kadouri and his colleagues are now conducting efficacy tests to determine the best way to administer such a treatment — but the fact that scientists are beginning to consider real alternatives to antibiotics is very promising. Even scaling back our use of antibiotics a little bit will ensure that these life-saving drugs last longer.
"The important thing is to start building an arsenal of other therapeutics," Kadouri said. "We need to get out of the mindset that it's just about antibiotics."
And, you have to admit that for a "natural" alternative, swallowing a bunch of predators to boost your immune system sounds pretty awesome.