Drug-resistant Shigella infections rising in US, CDC warns

Extensively drug-resistant (XDR) Shigella infections in the U.S. rose from 0% in 2011 to 8.5% of tested cases in 2023, federal health officials warn. Demographics have shifted from young children to adult men, with 86.2% of cases in adult males and high rates among immunocompromised and unhoused individuals. With no FDA-approved oral treatments available and hospitalization rates near 33%, the CDC calls for strengthened surveillance, rapid testing, and targeted prevention.

Rising prevalence and regional spread

• ▪In 2023, XDR Shigella infections accounted for 280 of 3,500 recorded cases (8%), with the Western U.S. recording 54% of total drug-resistant infections, followed by the Northeast at 38%.
• ▪The proportion of extensively drug-resistant (XDR) Shigella isolates in the United States increased from 0% during 2011–2015 to 8.5% in 2023, according to a report published in the CDC Morbidity and Mortality Weekly Report.

CDC surveillance of Shigella isolates

• ▪Among 505 analyzed XDR Shigella isolates from 2011 to 2023, 65.9% were Shigella sonnei and 34.1% were Shigella flexneri.
• ▪CDC researchers analyzed 16,788 Shigella isolates submitted to the CDC molecular surveillance network and PulseNet from January 1, 2011, to October 20, 2023.
• ▪CDC researchers identified 510 extensively drug-resistant isolates, representing 3.0% of the 16,788 Shigella samples with resistance data analyzed during the study.

Antibiotic resistance and treatment limitations

• ▪XDR Shigella strains resist commonly used oral antibiotics including ampicillin, azithromycin, ceftriaxone, ciprofloxacin, and trimethoprim-sulfamethoxazole.
• ▪There are currently no Food and Drug Administration (FDA)–approved oral antimicrobial treatments for extensively drug-resistant Shigella infections.

Populations affected and transmission routes

• ▪Among patients with available HIV status, 46.6% (54 of 116) reported HIV co-infection.
• ▪Epidemiologists and clinicians note that XDR Shigella strains are increasingly spreading through sexual contact among men who have sex with men (MSM) and unhoused populations.
• ▪Data from 2016 to 2023 indicate that XDR Shigella cases predominantly affected adult men, with 86.2% of patients being male and having a median age of 41 years.
• ▪Over 80% of XDR Shigella patients with travel history reported no recent international travel, suggesting local transmission within the U.S.

Hospitalization rates and Mortality outcomes

• ▪No deaths from the extensively drug-resistant Shigella strain have been reported in the United States.
• ▪Approximately one-third of patients with XDR Shigella infections required hospitalization, significantly higher than the typical 1% hospitalization rate for standard shigellosis.

CDC advice on prevention and care

• ▪Federal health officials called for strengthened surveillance, timely reporting, and targeted prevention strategies to limit the transmission of XDR Shigella strains.
• ▪The CDC recommends proper handwashing, avoiding swallowing water while swimming, safe food and water practices during travel, and abstaining from sex for two weeks after symptoms resolve.
• ▪The CDC advises individuals to seek medical attention if they experience bloody or prolonged diarrhea accompanied by fever, severe abdominal pain, dehydration, or a weakened immune system.

Shigella transmission and bacterial risks

• ▪Shigella is highly contagious because ingestion of as few as 10 organisms can trigger an infection and release illness-causing toxins.
• ▪Extensively drug-resistant Shigella bacteria can potentially transfer their resistance genes to other bacteria commonly residing in the human gut.

Annual shigellosis impact in US

• ▪Shigellosis results in approximately 6,000 hospitalizations and 40 deaths in the United States each year.
• ▪Shigella bacteria cause an estimated 450,000 infections annually in the United States, with symptoms including fever, stomach pain, and bloody or prolonged diarrhea.

Burden of drug-resistant infections

• ▪The CDC estimates that over 2.8 million drug-resistant bacterial infections occur annually in the United States, resulting in approximately 35,000 deaths.
• ▪Antimicrobial-resistant Shigella infections cause an estimated $93 million in direct medical costs in the United States annually.

Debatable claims

• ▪XDR Shigella poses an immediate public health threat to the general population
• ▪Sexual transmission is the primary driver of drug-resistant Shigella spread in the United States
• ▪Off-label antibiotic therapy is justified for treating XDR Shigella infections