Scientists from an Australian university have discovered another toxin used by Bacillus cereus.

Researchers at the Australian National University (ANU) showed how the toxin can infect cells, even when the body has fought off others.

The toxin, called NHE (non-hemolytic enterotoxin), attacks all types of cells in the body by anchoring itself and punching holes in the cell membrane, according to the study published in the journal Nature Communications.

Professor Si Ming Man and colleagues studied Bacillus cereus, which is responsible for producing toxins that cause diarrhea and vomiting, and for helping the bacteria to multiply.

“Now, we’ve discovered another toxin that’s equally capable of destroying cells. Or, to put it another way – we’re slowly learning the many tricks of bacteria – the toolbox they use to infect us. This means if one of the tools is lost or neutralized by the immune system, the bacteria have a back-up that still allows them to infect and cause disease,” he said.

There are an estimated 4.1 million cases of food poisoning in Australia, resulting in 31,920 hospitalizations, 86 deaths and one million visits to doctors on average every year.

Similarities between toxins
ANU researchers had previously found another toxin, called haemolysin BL (HBL), that is used to kill cells in the body and establish an infection. However, Bacillus cereus isolates that lack HBL can cause inflammation and disease in humans.

“The similarities between this toxin and the one our team has previously studied can be likened to the similarities between a mallet and a hammer. Our findings suggest they aren’t functionally identical – for example, one toxin might be better at killing a certain type of cells than the other. This could prove incredibly important when it comes to successful treatment,” said Professor Man.

Inflammasomes are important for host defense against pathogens. NHE from the foodborne pathogen Bacillus cereus is an activator of the NLRP3 inflammasome. However, individual components of NHE or all combinations of two of the three components did not trigger activation of the NLRP3 inflammasome.

Prevalence of NHE and HBL suggests that both toxins are key virulence factors important for the pathogenesis of Bacillus cereus infection. A better understanding of the host defense strategy to infection will be beneficial and neutralizing toxins might complement current therapies against infection caused by toxin-producing bacteria.

Antibiotic treatment for food poisoning may become less effective in the future due to bacteria’s growing resistance to antibiotics.

“We have created proteins that can neutralize the activity of the toxins. These proteins restrict the spread of the infection, and can be used to complement the existing antibiotic regime we use currently,” said Professor Man.