CDC Report Tracks Rise of Extensively Drug-Resistant Shigella Across the U.S.

A federal analysis spanning more than a decade of bacterial surveillance has confirmed that extensively drug-resistant Shigella is no longer a marginal phenomenon in the United States. The share of XDR isolates among all sequenced Shigella samples climbed from essentially zero during 2011 through 2015 to 8.5% by 2023, according to findings published April 9 in the Morbidity and Mortality Weekly Report.

The CDC's XDR Shigella Working Group reached that conclusion after examining 16,788 isolates submitted to PulseNet, the national molecular surveillance network for enteric pathogens, using whole-genome sequencing and antimicrobial susceptibility testing. Of those, 510 isolates, or 3.0% of the full dataset, met the XDR threshold. To qualify, a strain must be resistant to all five drugs that have historically anchored shigellosis treatment: ampicillin, azithromycin, ceftriaxone, ciprofloxacin, and trimethoprim-sulfamethoxazole. In practical terms, there are currently no FDA-approved oral antibiotics that reliably work against these strains, leaving clinicians with limited options when treating severe or complicated cases.

Species data were available for 505 of the 510 XDR isolates. Of those, 333, or 65.9%, were Shigella sonnei, while the remaining 172, or 34.1%, were Shigella flexneri. The distribution matters clinically because the two species carry somewhat different resistance profiles and transmission dynamics.

The epidemiologic pattern of XDR infections diverges from the typical picture of shigellosis as a foodborne or waterborne illness striking young children in institutional settings. Surveillance data have consistently shown elevated rates among men who have sex with men, people experiencing homelessness, international travelers, and immunocompromised individuals. Shigella spreads through the fecal-oral route and is highly infectious at very low doses, which makes sexual transmission and close-contact settings particularly efficient amplifiers of resistant strains.

The MMWR's publication came with specific guidance for the clinical and public health communities. Clinicians treating suspected shigellosis are urged to obtain cultures and susceptibility testing before prescribing rather than defaulting to empiric antibiotic therapy, a practice that can fail against XDR strains and may accelerate further resistance. Laboratories that identify known or suspected XDR isolates are directed to submit them to state or local public health labs, with whole-genome sequencing recommended wherever capacity exists. The report also called for prompt reporting of suspected outbreaks to public health authorities and heightened infection-control efforts in high-risk congregate settings, including shelters and childcare facilities.

Antibiotic stewardship runs as an explicit thread through the recommendations. Inappropriate antibiotic prescribing has contributed to the selective pressure that allows resistant strains to outcompete susceptible ones, and the CDC's guidance emphasized that antibiotics should be used only when clinically indicated. For people who do not require treatment, the core prevention tools remain unchanged: rigorous hand hygiene, exclusion of symptomatic children from childcare until they have recovered, and careful food-handling practices.

State and local health departments are expected to review their laboratory testing protocols and coordinate with the CDC on outbreak investigations where XDR strains are suspected. The trajectory documented in the MMWR, from a negligible fraction to nearly one in eleven sequenced isolates over 12 years, underscores how quickly a resistant phenotype can entrench itself in a bacterial population that spreads as efficiently as Shigella does.