Antibiotic-Resistant Shigella Spreads Rapidly Among Men Who Have Sex With Men in UK

A comprehensive genomic study by the University of Cambridge and the UK Health Security Agency has revealed that strains of the Shigella bacterium transmitted sexually between men are spreading twice as fast as typical strains and are developing antibiotic resistance at an alarming rate. Shigella, primarily known for causing dysentery through contaminated food and hands, is now endemic in certain sexual networks of men who have sex with men (MSM) in Western countries, spreading mainly through oral-anal contact.

The study analyzed 3,514 Shigella samples collected across the UK from 2004 to 2020, categorizing them into three groups: MSM cases without recent travel to endemic regions, other local cases, and travel-related cases. The sexually transmitted strains showed a geographic spread averaging 117 kilometers over two and a half years, compared to 46 kilometers for other local strains, indicating a faster and more extensive transmission. These strains also exhibited a higher number of distinct transmission chains and remained genetically distinct over 15 years, suggesting a sustained independent transmission cycle.

Antibiotic resistance was notably higher among the MSM-associated strains, with 70% resistant to at least one clinically relevant antibiotic, compared to 40% in other local strains. Between 2015 and 2020, the annual growth rate of these resistant strains increased by 15%. A particularly concerning strain resistant to ciprofloxacin, azithromycin, and ceftriaxone emerged shortly after the COVID-19 pandemic.

Professor Kate Baker, a lead researcher, emphasized the need for targeted public health messaging to affected communities, noting that multiple overlapping resistant strains require different treatment approaches than travel-related infections. Infectious disease specialist Dr. Roy Zucker from Israel confirmed similar clinical patterns in Israeli MSM populations, especially following large European Pride events.

Symptoms include persistent diarrhea, fever, nausea, and abdominal pain, with a short incubation period of one to three days. The study also linked rising azithromycin resistance to its previous widespread use in treating gonorrhea until 2018. Experts recommend sexual health clinics to inquire about patients' sexual histories and adjust treatments accordingly. Preventive measures include abstaining from sex for two weeks after symptoms resolve, thorough hygiene after anal contact, condom use, and avoiding sharing sex toys or internal cleansing equipment.