Microbiology

When Microbes Go Rogue

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Science  08 Jun 2012:
Vol. 336, Issue 6086, pp. 1213
DOI: 10.1126/science.336.6086.1213-a
CREDIT: JANICE HANEY CARR/CDC

In the gut, maintaining the peace is key—we live symbiotically with the trillions of microbes that inhabit this space, and rarely do any problems arise. But disruptions to this peace, as in the form of antibiotics, have the potential to cause disease. Ayres et al. explored this by treating mice with antibiotics and a chemical that causes colitis by disrupting gut epithelial cell integrity. Surprisingly, antibiotic- and chemical-treated mice did not develop colitis—instead, they developed a lethal, sepsis-like disease. Investigation into what caused septicemia in the mice revealed that it was the result of the outgrowth of an antibiotic-resistant strain of Escherichia coli that is normally present in the guts of healthy mice in small amounts. In accordance with Koch's postulates, injection of this strain of E. coli caused a sepsis-like disease in mice that were not treated with antibiotics or the colitis-inducing chemical. Disease depended on the Naip5-Nlrc4 inflammasome complex, which did not regulate bacterial growth but rather promoted immunopathology. This study illuminates how some microbes that we normally harbor without a problem can “go rogue”—with devastating effects—when the normal peace is disturbed.

Nat. Med. 18, 799 (2012).

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