Whole-genome sequencing reveals inter-household networks of gut-colonising ESBL- producing Escherichia coli in two rural Malawian districts

Abstract Infection with extended-spectrum beta-lactamase-producing Escherichia coli (ESBL-Ec) is a global health concern that disproportionately affects sub-Saharan Africa (SSA). Gut mucosal colonisation is thought to precede invasive infection. Understanding ESBL-Ec colonisation and transmission across communities is therefore essential. We investigated the genomic epidemiology and spatial structure of 159 gut-colonising ESBL-Ec isolates from the faeces of 211 people in two rural Malawian villages using longitudinal sampling (2023–24), whole-genome sequencing and household mapping. Colonisation prevalence rose from 34.1% (95% CI: 27.8–41.0) to 54.2% (95% CI: 46.0–62.3) over one year. Isolates belonged to 33 sequence types (STs), most commonly ST38 and ST131, harbouring 46 distinct antimicrobial resistance gene types. Fifteen strains were identified in ≥3 households that were typically separated by short geographic distances (