Cases of extensively drug-resistant Shigella infections are increasing in the United States, raising concerns about a diarrheal illness that can spread through sexual contact and has limited treatment options, according to a report from the Centers for Disease Control and Prevention.
Shigella is a highly contagious bacteria that can cause diarrhea, fever and stomach pain. It spreads through fecal-oral contact, contaminated food or water and sexual contact. Infection can occur after exposure to as few as 10 organisms.
By the numbers:
The CDC analyzed nearly 17,000 Shigella isolates collected from 2011 through Oct. 20, 2023. Among the 16,788 isolates with resistance data, 510 — or 3% — were classified as extensively drug-resistant, meaning they were resistant to five commonly used antibiotics: ampicillin, azithromycin, ceftriaxone, ciprofloxacin and trimethoprim-sulfamethoxazole.
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The percentage of isolates classified as extensively drug-resistant increased from 0% between 2011 and 2015 to 8.5% in 2023.
Most of the drug-resistant cases occurred in 2022 and 2023, with 415 cases, or more than 84% of the total, reported during those two years.
Why you should care:
The findings are particularly concerning because there are no Food and Drug Administration-approved oral antibiotics specifically available to treat extensively drug-resistant Shigella infections. Doctors may need to rely on laboratory testing to determine which medications, if any, are likely to work.
What they're saying:
The CDC report said sexual exposure information was incomplete and was not analyzed. However, previous studies have identified sexual contact among men who have sex with men as an important transmission route.
The patients with extensively drug-resistant Shigella were predominantly adults. Nearly 96% of patients with available age and sex information were at least 18 years old, and 86.2% were men. The median age was 41.
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Of the 258 patients with available hospitalization information, 97 — or 37.6% — were hospitalized. No deaths were reported.
HIV status was available for only 116 patients, 54 of whom reported an HIV co-infection. The CDC said people with weakened immune systems, including those living with HIV, may face a higher risk of severe illness and have fewer treatment options.
Most patients also did not report recent travel. Of the patients with available information, 76.2% reported no recent domestic travel and 82.4% reported no recent international travel, suggesting many infections were acquired within the United States.
What's next:
The CDC said the study likely underestimated the number of extensively drug-resistant infections because not all Shigella-positive specimens were cultured or genetically sequenced. Reporting and testing practices also varied by state and local jurisdiction.
Health officials urged clinicians to order antimicrobial susceptibility testing when possible and report cases promptly. The CDC said improved surveillance and targeted prevention strategies will be needed to limit the spread of drug-resistant Shigella strains.
The Source: The information in this story came from a Centers for Disease Control and Prevention analysis of 16,788 Shigella isolates submitted to PulseNet, the agency’s national molecular surveillance network, between Jan. 1, 2011, and Oct. 20, 2023. This story was reported from Los Angeles.