Extensively drug-resistant (XDR) Shigella infections have increased in the U.S. over the past decade, according to a recent analysis by the U.S. Centers for Disease Control and Prevention (CDC) published in Morbidity and Mortality Weekly Report.

XDR Shigella Cases Increased to 8.5 Percent in 2023

CDC analyzed 16,788 Shigella isolates collected through PulseNet between 2011 and October 2023. Among these, 510 isolates (3 percent) were identified as XDR. The proportion of XDR isolates rose from 0 percent during 2011–2015 to 8.5 percent in 2023. Moreover, the proportion of XDR Shigella among all isolates has increased.

XDR Shigella strains are defined as resistant to five commonly used antibiotics: ampicillin, azithromycin, ceftriaxone, ciprofloxacin, and trimethoprim-sulfamethoxazole.

CDC noted that no U.S. Food and Drug Administration (FDA)-approved oral antimicrobial treatments are available for XDR Shigella infections.

Most Cases Acquired Domestically

The analysis indicated a shift in the epidemiology of Shigella infections. Historically, U.S. outbreaks primarily affected children and involved drug-susceptible strains. In contrast, the majority of XDR cases occurred among adult men, who represented 86.2 percent of patients, with a median age of 41 years.

Travel history data suggested that most infections were domestically acquired. Among patients with available information, 76.2 percent reported no recent domestic travel, and 82.4 percent reported no recent international travel.

Transmission Risks and Public Health Implications

Shigella can be transmitted via the fecal-oral route, including through person-to-person contact, as well as through contaminated food. CDC emphasized that the bacteria are highly transmissible and capable of spreading antimicrobial resistance (AMR) genes to other enteric pathogens.

Given the rising prevalence of XDR strains and their transmission potential, CDC highlighted the need for strengthened surveillance, routine antimicrobial susceptibility testing, and timely reporting of shigellosis, which is a nationally notifiable disease.

The agency also called for targeted prevention strategies to limit further spread of XDR Shigella infections.