Live bacteria found in animal venom

Will people bitten by a spider or a snake be subject to double punishment? A new study published May 23, 2022 in the journal Microbiology Spectrum shows that live bacteria are present in the venom of these animals that could potentially cause infections.

At first it was believed that infections did not depend on the poison.

“Animal venoms are considered to be sterile sources of antimicrobial compounds with strong membrane-damaging activity against multidrug-resistant bacteria,” explains a team of British and American researchers and staff from the Venomtech laboratory. Thus, infections from bites from venomous animals have so far been thought to be independent of the venom, but rather associated with a wound that provides entry for pathogens.

“However, more than three-quarters of snakebite victims can develop mono- or polymicrobial wound infections characterized by Bacteroides, Morganella, Proteus and Enterococcus, bacterial taxa commonly found in the digestive system,” the biologists note. It has only been estimated that the snake’s mouth may contain foreign bacteria: if there are microorganisms, they therefore come from the insides of the prey eaten and persist after ingestion.

In this new study, scientists tried to find out if the venom contains its own live bacteria. They studied this through genetic analysis and poison cultures. If the results were convincing, they would try to find out by what genetic adaptations it is possible to survive in this poisonous substance, which in any case is an extreme environment. So the biologists analyzed the potential microbiota of five snake species, including the black-necked spitting cobra (Naja nigricollis) and two spider species, including the tarantula Poecilotheria regalis.

Bacteria that colonize poisons

“We found that all of the venomous snakes and spiders we tested had bacterial DNA in their venom,” study lead author Dr. Moschos said in a statement. “Contrary to the conventional wisdom that venoms are antimicrobial and sterile, despite conflicting reports since the 1940s, we show that microorganisms can viably colonize vertebrate and invertebrate venoms,” the researchers add. However, bacterial resistance to the toxin is not easy: gene adaptations are required to provide greater fluid resistance. The bacterial strains present have mutated.

Therefore, the treatment of people bitten by a snake or spider should not be limited to tissue damage or the administration of antivenom. The bacterial aspect should also be taken into account, especially for immunocompromised people and children. There are 2.7 million venom bite injuries each year, and 75% of victims are at risk of developing an infection.

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