The rise in domestic shigellosis and the genomic characteristics of <i>Shigella</i> clones linked to men who have sex with men in Taiwan, 2015‒2022

The rise of multidrug-resistant (MDR) and extensively drug-resistant (XDR) Shigella strains poses a growing global health threat, particularly among high-risk groups such as men who have sex with men (MSM). This study highlights the increasing prevalence of domestic shigellosis in Taiwan from 2015 to 2022, driven by the emergence of three MDR Shigella clones. These MSM-associated clones exhibit significantly higher resistance to azithromycin, extended-spectrum cephalosporins (ESCs), and ciprofloxacin compared to non-MSM-associated clones. Additionally, 14 extensively drug-resistant isolates were identified, carrying resistance genes for azithromycin and ESCs on IncFII or IncB/O/K/Z plasmids. Genomic analysis reveals that ciprofloxacin-resistant Shigella flexneri 2a (CipR_SF2) has become the most dominant clone, responsible for the majority of shigellosis cases since 2018, and is genetically distinct from strains observed in MSM-related outbreaks in other countries. By elucidating these clones' genetic characteristics and epidemiological trends, this research offers essential data for public health surveillance, helping to inform strategies for controlling the spread of MDR and XDR Shigella infections.