Extensively drug-resistant Shigella emerges in US, mostly among men

An analysis of CDC data reveals that extensively drug-resistant (XDR) Shigella has emerged in the United States, with the proportion of resistant isolates rising from 0% in 2011 to 8.5% in 2023. The outbreak primarily affects adult men, who make up 86.2% of cases, with a median age of 41. Sexual transmission among men who have sex with men is a key driver. Because these strains resist standard oral antibiotics, clinicians must rely on supportive hydration, avoid antimotility drugs, and hospitalize severe cases for intravenous therapy.

XDR Shigella prevalence trends

• ▪Historically, Shigella infections in the United States primarily occurred among children and were caused by strains that were susceptible to antibiotics.
• ▪The proportion of Shigella isolates characterized as extensively drug-resistant in the United States increased from 0% in 2011 to 8.5% in 2023, according to a report published by the CDC.

Transmission among men

• ▪The CDC report on extensively drug-resistant Shigella noted that 86.2% of individuals diagnosed with the infection were men.
• ▪Sexual contact among gay, bisexual, and other men who have sex with men is a notable transmission pathway for extensively drug-resistant Shigella.

High-risk patient populations

• ▪The median age of individuals who contracted extensively drug-resistant Shigella in the CDC report was 41 years, with only around 4% of cases occurring among children or adolescents.
• ▪Of the 116 individuals with extensively drug-resistant Shigella for whom HIV status was known, 46.6% were HIV-positive.
• ▪Multiple Shigella outbreaks have occurred among people experiencing homelessness over the past few years, driven by limited access to handwashing and sanitation.

Antibiotic resistance treatment challenges

• ▪Extensively drug-resistant Shigella species are resistant to ampicillin, azithromycin, ceftriaxone, ciprofloxacin, and trimethoprim-sulfamethoxazole, leaving no FDA-approved oral antimicrobials effective against them.
• ▪Resistance genes from extensively drug-resistant Shigella are located on transferable plasmids, which can potentially be transmitted to other enteric bacteria such as Escherichia coli.
• ▪Donald Dumford, MD, theorized that treatment or prophylaxis for other sexually transmitted infections using ciprofloxacin and azithromycin may have driven resistance within the Shigella population.

Prevention strategies for clinicians

• ▪Clinicians are advised to counsel patients with Shigella to wait 2 weeks after they are symptom-free before engaging in any sexual contact.
• ▪Clinicians should work with laboratories to run culture and sensitivity tests when encountering a patient with Shigella to ensure appropriate treatment and assist in public health surveillance.

Supportive care protocols

• ▪Clinicians are advised not to suggest antimotility agents like Imodium for Shigella patients, as these medications can prolong the length of bacterial shedding and illness.
• ▪Outpatients with severe cases of extensively drug-resistant shigellosis whose symptoms worsen require hospitalization, as starting intravenous antibiotics as an outpatient is not feasible.
• ▪For the majority of patients, shigellosis is a self-limited disease that resolves after roughly 7 days with supportive care, such as keeping up with fluids to prevent dehydration.