Gird your toilets, everyone: superbug strains of Shigella bacteria, a common diarrhea-causing infection, are becoming a larger problem.
Federal and state health officials detailed the trend in a recent report released by the Centers for Disease Control and Prevention. Since 2011, they found, an increasing percentage of Shigella cases documented nationwide have shown extensive resistance to all commonly used antibiotics. More needs to be done to prevent, track, and develop treatments against this growing public health danger, they warn.
“[Extensively drug-resistant] Shigella infection is an emerging concern in the United States,” the authors wrote in their paper, published late last week in the Morbidity and Mortality Weekly Report (MMWR).
Hardy bugs
Antibiotic resistance has become a widespread public health threat over time. Antibiotic resistant bacteria are now estimated to kill over 1.2 million people worldwide every year. By 2050, that annual death toll could reach 10 million, putting it on par with yearly cancer deaths.
Though there are many kinds of superbug bacteria out there, extensively drug-resistant, or XDR, Shigella might be one of the most worrying ones. These bacteria can resist all classes of antibiotics routinely used to treat them, including azithromycin, ceftriaxone, and ciprofloxacin. As of now, there is no oral antibiotic approved to handle these hardy infections.
Shigella infection, or shigellosis, is a nationally notifiable disease, meaning doctors are obligated to report any detected cases to their health departments. Since at least 2015, CDC and local health officials have been noticing an increase in cases of XDR shigellosis. According to the report’s authors, though, the patterns of this rise haven’t been fully fleshed out until now.
The researchers analyzed data collected from PulseNet, a national laboratory network used to identify and track bacteria that cause food- and waterborne outbreaks. They specifically examined samples of Shigella bacteria sent to labs across the country between 2011 and 2023.
Between 2011 and 2015, zero samples contained XDR Shigella, they found. By 2023, however, 8.5% of the samples submitted that year were extensively resistant. Two-thirds of these cases were from Shigella sonnei, the most common culprit of shigellosis in general, while the rest were from Shigella flexneri. Three-quarters of cases had no recent travel history, suggesting their infections were caught locally. In cases with known information, one-third were ultimately hospitalized as a result of their infection, though no deaths were reported.
A growing danger
Shigellosis is often a miserable time, with most people experiencing diarrhea, fever, and stomach pain. The infection usually clears up on its own in a week’s time, even without antibiotics. But these drugs are still needed to treat severe cases, or to prevent life-threatening illness in high-risk groups like immunocompromised individuals.
It’s estimated that 450,000 Americans are infected with Shigella bacteria every year. Though Shigella is typically spread from eating contaminated food and water, it can also be transmitted through close sexual contact, particularly if it involves anal sex. The latter seems to be one major reason why recent outbreaks of XDR Shigella have been concentrated among men who have sex with men.
It’s not just the bacteria themselves that are a problem, but the genes they’ve evolved to develop this resistance. Some of these same resistance genes can potentially be passed onto other bacteria commonly found in the gut. This risk, coupled with how highly contagious these bacteria are, only further heightens their danger to the public, the researchers say.
Doctors should rely on lab testing to guide their treatment of suspected Shigella infections whenever possible, the authors say, and they should report XDR cases in a timely fashion to help cut off outbreaks. It’ll also be important to find or develop antibiotics that can tackle these infections.
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