Testing antibiotics (Credit: CDC/Don Stalons)
Bacteria continue to acquire resistance to antibiotics at a terrifying rate, and pharmaceutical makers have far too few possibilities for effectiveness new replacements in development. So, up to a point, it’s good news this week that at least a couple more novel candidates have turned up—in some of the least sanitary, least likely places one might imagine. I’ll keep my enthusiasm under wraps for reasons I’ll discuss presently, but first: where are these new leads for antibiotics coming from?
In the brains of cockroaches and locusts
At the Society for General Microbiology meeting at the University of Nottingham, Simon Lee reported that his group at the university’s School of Veterinary Medicine and Science had isolated proteins with powerful antibiotic properties from the brains of insects.
The researchers discovered nine different chemicals in the brains of locusts and cockroaches, which all had anti microbial properties strong enough to kill 90% of MRSA (Methicillin-resistant Staphylococcus aureus) while not harming human cells.
“A kill rate of 90% is very very high, and I diluted the substance down so there was only a minute amount there. Conventional antibiotics reduce the number of the bacteria and let your immune system cope with the rest. So to get something with such a high kill rate that is so potent at such a low dose is very promising”
Alexander Fleming’s discovery of penicillin is one of the great tales of a medical breakthrough drawn from nature. While growing cultures of staphylococci, he noticed that one dish was contaminated with a mold that had killed all the bacteria adjacent to it. The mold, Fleming learned, had a natural capacity to clear away bacteria by lysing their cell walls. And so the age of antibiotics began.
American cockroach (Credit: Colin Ybarra)
The rationale for the researchers choosing to look inside insect pests for antibiotics seems to be that because cockroaches can thrive in filthy environments, they must have ways to protect themselves against lethal infections. The Nottingham researchers are certainly not the first to have that insight. Insects do have astonishingly sophisticated innate immune systems that are built around antimicrobial compounds; they lack an adaptive immune system, like ours, that manufacture antibodies and lymphocytes against specific invaders.
But why would these antibiotic proteins only be found in the cockroaches’ nervous systems and not their other tissues, which are of course equally subject to infection?
“They must have some sort of defense against micro organisms. We think their nervous system needs to be continuously protected because if the nervous system goes down the insect dies. But they can suffer damage to their peripheral structures without dying,” he told BBC News.
Well… maybe. Given that cockroaches can technically survive without heads (and brains) for weeks and yet removing other parts of their body can significantly impair their learned behaviors (according to Scientific American), I’m not convinced it’s open and shut that they need their nervous systems uniquely more than other tissues. Still, that’s almost beside the point: if these compounds hold real promise as antibiotic drugs, we’ll take them.
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