Alligators often engage in violent fights over territories and mates, and scientists have puzzled over why their wounds rarely get infected.
Now researchers think the secret lies in the reptiles' blood.
Chemists in Louisiana found that blood from the American alligator can successfully destroy 23 strains of bacteria, including strains known to be resistant to antibiotics.
In addition, the blood was able to deplete and destroy a significant amount of HIV, the virus that causes AIDS.
Study co-author Lancia Darville at Louisiana State University in Baton Rouge believes that peptides—fragments of proteins—within alligator blood help the animals stave off fatal infections.
Such peptides are also found in the skin of frogs and toads, as well as in Komodo dragonsand crocodiles. The scientists think that these peptides could one day lead to medicines that would provide humans with the same antibiotic protection.
"We are in the process of separating and identifying the specific peptides in alligator blood," said Darville, who presented the findings on Sunday at the 235th national meeting of the American Chemical Society in New Orleans.
"Once we sequence these peptides, we can obtain their chemical structure to potentially [create new] drugs."
Study co-author Mark Merchant, a biochemist at McNeese State University in Lake Charles, Louisiana, was among the first to notice alligators' unusual resistance.
He was intrigued that, despite living in swampy environments where bacteria thrive, alligators that suffered frequent scratches and bruises rarely developed fatal infections.
Merchant therefore created human and alligator serum—protein-rich blood plasma that has had clotting agents removed—and exposed each of them to 23 strains of bacteria.
Human serum destroyed only eight of the bacterial strains. But the alligator serum killed all 23, including drug-resistant bacteria such as MRSA (methicillin-resistant Staphylococcus aureus).
(Related news: "Drug-Resistant Bacteria Found in Wild Arctic Birds" [January 24, 2008].)
When the alligator serum was exposed to HIV the researchers found that a good amount of the virus was destroyed.
The study team thinks that pills and creams containing alligator peptides could be available at local pharmacies within seven to ten years.
Such products would be a boon to patients that need extra help preventing infections, such as diabetes patients with foot ulcers, burn victims, and people suffering from auto-immune diseases.
But there may be potential hurdles before alligator-based medicines can reach drugstore shelves.
For example, Darville noted, initial tests have revealed that higher concentrations of the alligator serum tend to be toxic to human cells.
Not So Primitive
Adam Britton is a biologist based in northern Australia who has found similar antimicrobial proteins called crocodillins in the blood of crocodiles.
Antimicrobial peptides in crocodiles and alligators are part of the animals' innate immune systems, Britton said, which provide automatic protection from certain diseases.
By contrast, human immunities are adaptive—people develop resistance to many diseases after exposure, such as the low doses given in vaccines.
Although innate immunity is often considered primitive, there is nothing primitive about its effectiveness, Britton said.
Innate immunities "usually serve to amplify the adaptive immune system, often by weakening the membranes of bacteria," he said.
"It appears that alligator and crocodile antimicrobial peptides are extremely effective agents" against bacteria, he added.
Britton hopes to use Australian crocodile blood to complement the latest work on alligators and answer questions about what these proteins mean for immune systems in general.
"If we can harness these secrets," Britton said, "we could be on the verge of a major advance in medical science."