New study uncovers key virulence mechanism in community-associated MRSA strains

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A component of the outer envelope in Staphylococcus aureus could be responsible for elevated virulence in strains of community-associated MRSA (CA-MRSA) according to a study recently published in Nature Microbiology. The researchers have suggested that this mechanism could be a target for future anti-infective strategies.

CA-MRSA primarily causes severe skin and soft tissue infections, which can be severe even in healthy individuals. The underlying pathomechanisms of these infections have never previously been understood, and some aspects of the bacteria’s virulence mechanisms have been subject to debate.

Utilizing mouse models, the researchers observed that induction of skin abscesses was positively correlated with the levels of a cell wall component, termed wall techoic acid (WTA). The team then demonstrated that, when compared with bacteria possessing low levels of WTA, bacteria with high levels of WTA were more active in inducing abscess formation.

In addition, the group discovered this mechanism was mediated by T cells; suggesting that increased amounts of WTA in the cell wall enables CA-MRSA to be more immunologically active.

Author Christopher Weidenmaier, from the Interfacultary Institute for Microbiology and Infection Medicine (IMIT) (Germany), explained: “It’s well-known that CA-MRSA strongly increases the secretion of toxins, which plays a major role in the serious progression of skin infections. We’ve now also been able to prove that the increased insertion of the sugar polymer into the cell envelope creates a change in the immune reaction in the case of skin infections.”

“This increased the ability of these aggressive bacteria to cause particularly serious skin infections in animal experiments. However, additional research is required to determine if the results also hold true in humans.”

This study is the first to show that WTA is directly involved in Staphylococcus aureus virulence. The insight provided by this mechanism could provide opportunities for the development of novel anti-infective strategies.

Weidenmaier commented: “This kind of therapeutic approach would give the human immune system the chance to combat the infection more efficiently itself. In contrast to classic antibiotic treatment, an anti-virulence strategy should lead to lower resistance rates.”

Source: Wanner S, Schade J, Keinhörster D et al. Wall teichoic acids mediate increased virulence in Staphylococcus aureus. Nat. Microbiol. 2, 16257 (2017) www.dzif.de/en/news_media_centre/news_press_releases/view/detail/artikel/scientists_decipher_a_mechanism_in_serious_skin_infections/

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