Abstract:
Background: Multidrug‑resistant (MDR) diarrheagenic Escherichia coli (DEC) are a leading cause of morbidity and treatment failure among children under five, yet Kenyan data on circulating DEC pathotypes, resistance profiles, and modifiable risk factors remain scarce. Objective: To characterise DEC pathotypes isolated from stool samples of under‑five children in Nakuru County Referral Hospital, describe their phenotypic and genotypic resistance to selected β‑lactams, and identify environmental, clinical and behavioural determinants—including household water quality and recent steroid therapy—associated with antimicrobial resistance. Methods: We conducted a hospital‑based matched case–control study (1: 1) between November 2017 and October 2018. Cases (n = 192) were children harbouring β‑lactam‑resistant DEC; controls (n = 192) carried susceptible DEC and were matched by age and sex. DEC pathotypes were confirmed by multiplex PCR, antimicrobial susceptibility by CLSI disc‑diffusion, and ESBL genes by conventional PCR. Structured caregiver interviews captured antibiotic access, water‑handling practices, and systemic steroid use. Conditional logistic regression estimated adjusted odds ratios (aOR). Results: EAEC predominated (40 %), followed by ETEC (32 %) and EPEC (28 %). Seventy‑two percent of isolates were resistant to ≥ 3 antibiotic classes, and blaCTX‑M was detected in 45 %. Independent predictors of MDR DEC were self‑medication with β‑lactams in the previous three months (aOR 6.2, 95 % CI 3.9–9.4), use of untreated household water (aOR 3.4, 1.8–6.2), and recent systemic steroid therapy (aOR 2.6, 1.4–4.7). Water isolates shared identical ESBL genotypes with paired stool isolates in 78 % of households. Conclusion: MDR DEC, especially EAEC harbouring blaCTX‑M, are widespread among Nakuru under‑fives. Unregulated β‑lactam access, steroid exposure, and contaminated household water together accelerate resistance. Strengthening community antibiotic stewardship, limiting non‑prescription sales, and promoting point‑of‑use water treatment are urgent priorities
