Bite from common Irish spider can transmit antibiotic-resistant bacteria

1 Dec 2020

A noble false widow spider. Image: NUI Galway

Researchers from NUI Galway have found the bite of a noble false widow spider can contain harmful bacteria resistant to common antibiotic treatments.

After discovering that the venom of a noble false widow spider is more similar to a black widow’s venom than we once thought, NUI Galway researchers have now found that it also contains rather harmful bacteria.

Writing in Scientific Reports, the team of zoologists and microbiologists said that common house spiders carry bacteria susceptible to infect people, with the noble false widow also carrying harmful strains resistant to common antibiotic treatments.

The discovery helps confirm a long-held theory among spider and healthcare specialists and helps explain the range of symptoms experienced by those who have been bitten by a noble false widow spider.

While Australian black widows and funnel web spiders are known for their deadly venomous bites, rare skin-eating conditions brought on by the bites of seemingly harmless European and North American spiders were somewhat of a mystery. It was initially thought that this must be the result of a secondary infection caused by the victim scratching the area or touching it with contaminated fingers.

Furthermore, many spiders have been shown to have venom with antibacterial activity and it is often debated as to whether the venom would neutralise bacteria at the bite site. The researchers said this discovery also demonstrates that, at least for the noble false widow, the venom does not inhibit bacteria.

A cause for concern

“The diversity of microbes never ceases to amaze me,” said Dr Aoife Boyd, director of the pathogenic mechanisms group at NUI Galway’s School of Natural Sciences.

“The power to survive and thrive in every environment is shown here by the presence of antimicrobial resistance bacteria, even in spider venom. Antimicrobial resistance is an urgent and growing problem worldwide.”

Around 10 species of spiders common to north-west Europe have fangs strong enough to pierce human skin, but most bites just leave some redness and pain. Only a bite from the noble false widow is considered of medical concern.

Neyaz Khan, co-lead author of the study and a PhD student at the pathogenic mechanisms group in NUI Galway, said this study shows that “spiders are not just venomous but are also carriers of dangerous bacteria capable of producing severe infections”.

“The biggest threat is that some of these bacteria are multi-drug resistant, making them particularly difficult to treat with regular medicine,” he said. “This is something that healthcare professionals should consider from now on.”

The noble false widow is a relative newcomer to Ireland, having spread across the world only in the last 20 years. It is now a common species of spider in and around urban habitats.

Colm Gorey was a senior journalist with Silicon Republic