Frog skin germ-fighting substances for new antibiotics

Even witchdoctors in the past knew that some frog skins contain germ-fighting substances since they manage to live in swampy and hostile environments. A group of scientists, led by Michael Conlon, Ph.D., noted that modified frog skin substances could be used against the emergence of drug-resistant bacteria, which have the ability to shrug off conventional antibiotics.

“Frog skin is an excellent potential source of such antibiotic agents”, said Conlon, a biochemist at the United Arab Emirates University in Al-Ain, Abu Dhabi Emirate. “They’ve been around 300 million years, so they’ve had plenty of time to learn how to defend themselves against disease-causing microbes in the environment. Their own environment includes polluted waterways where strong defenses against pathogens are a must.”

Researchers have attempted to isolate germ-fighting chemicals and make them suitable for development into new antibiotics. However, the solution has been elusive because those antibiotics tend to be toxic to human cells and certain chemicals in the bloodstream easily destroy them. Conlon and colleagues described an approach to overcome these problems. They discovered a way to tweak the molecular structure of frog skin antibiotic substances, making them less toxic to human cells but more powerful germ killers. Similarly, the scientists also discovered other tweaks that enabled the frog skin secretions to shrug off attack by destructive enzymes in the blood. The result was antibiotics that last longer in the bloodstream and are more likely to be effective as infection fighters.

The antibiotic substances work in an unusual way that makes it very difficult for disease-causing microbes to develop resistance. The scientists are currently screening skin secretions from more than 6,000 species of frogs for antibiotic activity. So far, they have purified and determined the chemical structure of barely 200.

One substance isolated from the skin secretions of the Foothill Yellow-legged Frog (a species once common in California and Oregon but now facing extinction) shows promise for killing methicillin-resistant Staphylococcus aureus (MRSA) bacteria. MRSA is a “superbug” infamous for causing deadly outbreaks of infection among hospitalized patients.  Another example is the skin of the mink frog which contains secretions that show promise for fighting “Iraqibacter” caused by multidrug-resistant Acinetobacter baumanni.

Conlon predicts that some of the substances could make their way into clinical trials within the next five years. He envisions that pharmaceutical companies could develop the chemicals as creams or ointments for treating skin infections or as injectable drugs for treating drug-resistant infections throughout the body.

“The research is also important because it underscores the importance of preserving biodiversity”, Conlon said. “Some frog species — including those that may contain potentially valuable medicinal substances — are in jeopardy worldwide due to loss of habitat, water pollution, and other problems.”