Alarm Bells Ring as New Strain of Drug-Resistant Shigella Emerges in Los Angeles

In a startling discovery, researchers in Los Angeles have identified a highly resistant strain of Shigella bacteria, which poses a significant threat to public health. Over a three-month period this year, three men sought medical attention at various clinics and emergency rooms in Los Angeles County, presenting with severe diarrhea and a history of recent sexual contact with other men.

Stool cultures taken from these patients revealed an infection from Shigella sonnei, which is already known for its resistance to five classes of commonly prescribed antibiotics. However, what makes this case particularly alarming is that further genetic analysis uncovered a unique mutation in the bacteria, granting it resistance to cephalosporins—medications typically used as a last resort when other treatments fail.

Dr. Shangxin Yang, a molecular biologist and clinical microbiologist from UCLA and one of the co-authors of the research, highlighted the strain’s exclusivity to Los Angeles, noting that it has not been reported elsewhere. Although the patients have since recovered, this new mutation underscores a worsening battle against an increasingly resilient pathogen. "It's very alarming," Yang warned, emphasizing the stealthiness of the bacteria and its ability to spread rapidly within communities.

This year, the U.S. Centers for Disease Control and Prevention (CDC) began monitoring a surge in extensively drug-resistant (XDR) shigellosis cases across the country. Los Angeles County reported 45 XDR shigellosis cases in 2023—up from just five in 2021—with the majority of infections reportedly occurring among men who have sex with men.

While the incidence appears to have decreased from its peak, with 30 cases recently reported, experts stress that Shigella sonnei continues to pose serious challenges. Many individuals infected with Shigella may show no symptoms or only mild ones, leading them to unknowingly transmit the infection to others.

Dr. Daniel Uslan, an infectious disease specialist at UCLA and co-author of the study, noted that such infections often resolve on their own, but for individuals with weakened immune systems, the outcomes can be grave. One patient, a 62-year-old man with a history of HIV/AIDS and hepatitis C, required intensive care after succumbing to septic shock. He was successfully treated with meropenem, an antibiotic reserved for severe infections that do not respond to other drugs.

Despite the challenges posed by this new strain, experts encourage a measured response rather than panic. "This is not a cause for panic. It's a cause for caution and alarm," noted Uslan, as the emergence of new drug-resistant bacteria raises concerns within the broader context of antibiotic resistance.

A February 2023 study published in the medical journal Lancet highlighted the potential future ramifications of such "superbugs." The research estimated that without new antibiotic developments, nearly 2 million people could succumb to superbug infections by 2050—a staggering increase from the 1.14 million fatalities recorded in 2021, coupled with millions more affected by related conditions.

The World Health Organization has echoed these concerns, pointing out the striking scarcity of new antibiotics under development. Health leaders, such as Henry Skinner from the AMR Action Fund, have stressed the urgent need for innovative solutions to combat these resistant strains, especially those significantly impacting urban centers like Los Angeles.

As the fight against antibiotic resistance continues, health officials and researchers are calling for collective vigilance and greater investment in the development of next-generation antimicrobial therapies to confront evolving threats head-on.