Multidrug-resistant conjugative plasmid carrying mphA confers increased antimicrobial resistance in Shigella

Shigellosis is a common gastrointestinal disease in developing countries, primarily in children under five. Azithromycin (AZM) is the first-line treatment in Bangladesh, along with ciprofloxacin (CIP) and ceftriaxone (CRO). A study of 2407 clinical isolates from 2009 to 2016 found that AZM resistance increased from 22% to 60%, CIP resistance by 40%, and CRO resistance from zero to 15%. The key macrolide resistance factor in Shigella was the mphA gene, and a 63MDa conjugative middle-range plasmid harbored AZM and CRO resistance factors. The rapid spread of resistance genes among Shigella is driven by horizontal gene transfer rather than direct lineage.