A dangerous diarrhea-causing superbug is spreading in Los Angeles

A diarrhea-causing superbug is causing trouble in Los Angeles. Researchers have discovered an alarming new strain of Shigella bacteria in the area – one that can resist almost any antibiotic thrown at it.

Scientists from the University of California, Los Angeles conducted the study, which looked at an unusual cluster of Shigella cases detected between 2023 and 2024 Each of the cases was found to carry an extensively drug-resistant (XDR) strain of the bacteria. Although all the victims have recovered, the researchers say their discovery is “alarming,” especially since it’s likely the superbug is still actively spreading in LA and possibly elsewhere.

Shigella is a routine source of diarrhea and other gastrointestinal symptoms. While most cases cause only a week-long bout of suffering that resolves on its own, the infection can rarely cause severe, even fatal complications, especially in people with weakened or underdeveloped immune systems, such as very young children. Shigella kills about 200,000 people worldwide annually; in the US it is a thought to infect about half a million people each year, resulting in thousands of hospitalizations. The germ is usually spread through contaminated food or drink, but it can also be sexually transmitted. This latter form of transmission tends to occur more often through anal contact among men who have sex with men.

Antibiotics are used to treat severe Shigella infections or to keep infections under control in those at higher risk of disease. But as with many other bacteria, Shigella bacteria are increasingly learning how to repel the most common antibiotics used against them. The most troublesome strains are broadly drug-resistant, meaning they can overcome a wide variety of antibiotics. In their newspaper, published this month in Journal of Infection Controlscientists at the University of California, Los Angeles detail the discovery of a new XDR strain of Shigella sonnei in three of their patients.

According to the report, the three cases were discovered within a three-month period between 2023. and 2024 All three infections involved men who had a history of sex with other men, with one patient reporting that their recent sexual partner had been diagnosed with Shigella a week earlier. Initial laboratory tests revealed that they carried the XDR strain, officially defined as resistant to the antibiotics azithromycin, ciprofloxacin, ceftriaxone, trimethoprim-sulfamethoxazole and ampicillin.

ULCA scientists performed genetic analysis on samples collected from their patients. They found that all three patients carried a similar strain, although it was markedly different from past XDR strains identified in other parts of the world. This likely means that this version has been developing and spreading in the area for some time, the researchers say.

“The discovery of a new XDR S. sonnei active spread in Los Angeles is alarming,” they wrote.

Fortunately, the cases themselves were still treatable or otherwise cleared up on their own. One person did develop a severe infection and ended up in intensive care. But the real-time detection of XDR resistance in this case prompted doctors to switch to another recommended drug, which seemed to work, and the patient eventually made a full recovery.

However, the advent of XDR Shigella in the US and worldwide is a serious and growing public health problem. These cases are obviously more difficult to treat than typical cases Shigella infection and the delay in finding the right drug that works against an XDR strain can potentially be fatal. Last year, scientists from the Centers for Disease Control and Prevention issued public health advisory on the superbug. In the advisory, the CDC reports that about 5% of Shigella cases reported to the agency in 2022 were caused by XDR strains, up from 0% in 2015. Given these recent cases, the problem has probably only gotten worse since then. And UCLA scientists say more needs to be done to identify and limit the spread of these dangerous bacteria.

“These cases highlight the rapid growth of XDR Shigella in the US and an urgent need for appropriate detection and management,” they wrote.