New potential strategies against superbugs

Staphylococcus aureus Researchers have discovered a toxin – SElX – released by methicillin-resistant Staphylococcus aureus (MRSA) which leads the body’s immune system to go into overdrive and damage healthy cells. SElX is made by 95 per cent of S. aureus strains, making it a potential drug target to fight this hospital superbug. SElX belongs to a family of toxins known as superantigens that can invoke an extreme immune response. When it is released it triggers an over multiplication of immune cells, which can lead to high fever, toxic shock and potentially fatal lung infections looked at a strain of MRSA known as USA300 that can cause severe infections in otherwise healthy individuals. If we can find ways to target this toxin, we may be able to stop it from triggering an over-reaction of the body’s immune system and prevent severe infections.

A Novel Core Genome-Encoded Superantigen Contributes to Lethality of Community-Associated MRSA Necrotizing Pneumonia. (2011) PLoS Pathog 7(10): e1002271. doi:10.1371/journal.ppat.1002271


Other research has linked a naturally occurring mutation in the bacterium Clostridium difficile to severe and debilitating diarrhoea in hospital patients undergoing antibiotic therapy. These antibiotics destroy the “good” bacteria in the gut, which allows this “bad” bacterium to colonise the colon, where it causes bowel infections that are difficult to treat. The mutation wipes out an inbuilt disease regulator, called anti-sigma factor TcdC, producing hypervirulent strains of C. difficile that are resistant to antibiotics and which have been found to circulate in Canada, the US, UK, Europe and Australia. The results suggest that bacterial strains carrying this mutation have the potential to produce more of the harmful toxins that cause disease in susceptible individuals – commonly patients aged 65 years or over. As we now have a better understanding of these strains, we can design new strategies to prevent, control and treat these infections.

The Anti-Sigma Factor TcdC Modulates Hypervirulence in an Epidemic BI/NAP1/027 Clinical Isolate of Clostridium difficile. (2011) PLoS Pathog 7(10): e1002317. doi:10.1371/journal.ppat.1002317


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