Drug-Resistant Shigella Strains Rise, Posing Treatment Challenges

An increase in antibiotic-resistant strains of Shigella, the bacteria that causes Shigellosis, is making the infection more difficult to treat, according to a recent report from the Centers for Disease Control and Prevention (CDC).

The CDC tracked nearly 17,000 Shigella samples collected between 2011 and 2023. In 2023, 8.5% of samples with resistance data were classified as extensively drug-resistant (XDR), meaning they were resistant to all five antibiotics in the CDC's definition. This is a significant rise from 2011-2015, when no samples were classified as XDR.

Shigellosis symptoms include diarrhea, fever, and abdominal cramps. While case counts have remained steady, the bacteria are evolving, leading to diminishing treatment options, according to Dr. Tyler Evans, an infectious disease physician and CEO of Wellness Equity Alliance. Currently, there is no FDA-approved oral antibiotic for XDR Shigella.

Shigella bacteria can spread through tiny amounts of fecal matter, including via contaminated food or water, unwashed hands, or sexual activity. While not typically classified as a sexually transmitted infection, it can be transmitted through sex when fecal matter comes into contact with another person's mouth, according to Dr. Andi Toufexis, a family medicine physician specializing in sexual health. Sexual transmission has been documented since the 1970s, but the rise in XDR strains is a more recent concern.

The CDC report indicated that most patients with XDR Shigella were adult men, with a median age of 41. Of those with known HIV status, nearly half were living with HIV. Individuals experiencing homelessness and those with weakened immune systems may also be at heightened risk. Children under 5 are particularly susceptible, and many past outbreaks in the U.S. were linked to childcare settings and schools, though those earlier outbreaks primarily involved antibiotic-susceptible strains.

Of the XDR cases analyzed by the CDC, 37.6% required hospitalization, but no deaths were reported. The CDC notes that infections may be undercounted as not all positive specimens are tested for resistance. Most patients with available travel histories had not traveled internationally recently, though this information was missing for many.

Experts advise that while people should be concerned, they should not panic. Most Shigella infections resolve on their own, but severe cases may require medical treatment. Physicians recommend against taking antidiarrheal medications like Imodium, as they can slow the gut and potentially hinder the body's ability to flush out the bacteria. Instead, seeking medical advice is advised for suspected Shigella infections.

To reduce the risk of infection, doctors recommend practicing good hygiene, including thorough handwashing before preparing food and before and after sex. Using condoms or dental dams during sexual activity and cleaning sex toys after each use can also help. If a partner has diarrhea, it is advisable to avoid sex and wait at least two weeks after symptoms have completely resolved before resuming sexual activity.