Cockroaches may be nasty bugs, but they could help fight even nastier ones. New research finds that the rudimentary brains of cockroaches and locusts teem with antimicrobial compounds that slay harmful E. coli and MRSA, the antibiotic-resistant staph bacterium. The work could lead to new compounds for fighting infectious diseases in humans.
Extracts of ground-up brain and other nerve tissue from the American cockroach, Periplaneta americana, and desert locust, Schistocerca gregaria, killed more than 90 percent of a type of E. coli that causes meningitis, and also killed methicillin-resistant staph, microbiologist Simon Lee reported September 7 at the Society for General Microbiology meeting at the University of Nottingham in England.
“Some of these insects live in the filthiest places ever known to man,” says Naveed Khan, coauthor of the new study. “These insects crawl on dead tissue, in sewage, in drainage areas. We thought, ‘How do they cope with all the bacteria and parasites?’”
Khan and his colleagues became intrigued by insect antimicrobials when they noticed that many soldiers were returning from the Middle East with unusual infections, yet locusts living in the same areas were unperturbed. So the researchers, all from the University of Nottingham, began investigating how the insects ward off disease.
The team ground up various body parts from both cockroaches and locusts that had been reared in the lab and incubated them for two hours with different bacteria. Leaving these mixtures overnight on petri dishes revealed that the extracts from brains and from locust thorax nerve tissue killed nearly 100 percent of the bacteria.
Yet the insect brain extracts didn’t seem to bother human kidney or epithelial cells when grown with them in a lab dish.
Curiously, extracts of insect fat, muscle and blood didn’t bother the bacteria at all. Cockroaches and locusts often eat stuff loaded with microbes, says parasitologist Carl Lowenberger of Simon Fraser University in Burnaby, Canada, so you would think insect guts and blood, which bathes the organs, would have similar antimicrobial activity.
Nine molecules appear to be responsible for the antimicrobial activity in locust tissue, although they have yet to be identified. The team is also still working out the details of the cockroach compounds.
The compounds may work together as a cocktail, Lowenberger says. Insects make hundreds of antimicrobial compounds, and it may be that very high concentrations of those molecules would be required for fighting an infection in humans. But the research “is pretty neat stuff,” he says. And perhaps down the road, the yet-unidentified molecules will prove useful in fighting infections in people.
