Cluster of Extensively Drug-Resistant Shigella sonnei Carrying blaCTX-M-15 in Los Angeles, California, 2023-2024

A case of extensively drug-resistant (XDR) Shigella flexneri 2a was reported in an immunocompetent MSM in Los Angeles, CA, following a UK outbreak. The case involved three patients with XDR Shigella sonnei, which are resistant to azithromycin, ciprofloxacin, ceftriaxone, trimethoprim-sulfamethoxazole, and ampicillin. All patients were MSM and had histories of high-risk sexual behavior. The first patient, a 62-year-old male with a history of HIV/AIDS and hepatitis C, presented with severe diarrhea and was admitted to the ICU for septic shock. He was initially treated with meropenem, then switched to azithromycin. The second patient, a 29-year-old HIV-negative male, presented with diarrhea and was initially treated with ciprofloxacin. The third patient’s diarrhea resolved, and no further treatment was provided.