Association of Corticosteroid Utilisation with Amoxicillin-Resistant Diarrhoeagenic Escherichia coli Among Children Under Five in Nakuru, Kenya: A Matched Case-Control Study

Diarrhoeagenic Escherichia coli (DEC) causes childhood diarrhoea, while antimicrobial resistance limits treatment. Systemic corticosteroids are used for paediatric asthma and allergy, but their relationship with resistant enteric infection in African children is unclear. We assessed the association between corticosteroid utilisation and amoxicillin-resistant DEC among children under five years in Nakuru County, Kenya. A hospital-based case-control study with 1:1 matching at recruitment was conducted from November 2017 to October 2018. Of 1,124 children screened, 384 had laboratory-confirmed DEC: 192 amoxicillin-resistant cases and 192 susceptible controls. Caregivers reported allergy/asthma medication use in the preceding 12 months. Susceptibility was determined by Kirby-Bauer disc diffusion. Medication associations were estimated from observed exposure counts as crude odds ratios (cORs) with 95% confidence intervals (CIs). Among cases, co-resistance occurred to ampicillin in 168/192 (87.5%) and erythromycin in 156/192 (81.3%). Corticosteroids were reported for 177/384 (46.1%) children and antihistamines for 127/384 (33.1%). Relative to the do-not-know/none category, corticosteroid utilisation was associated with higher odds of resistant DEC (cOR 2.71, 95% CI 1.57-4.66; p<0.001), whereas antihistamine utilisation was associated with lower odds (cOR 0.53, 95% CI 0.30-0.95; p=0.023). Corticosteroid utilisation was associated with amoxicillin-resistant DEC, but the crude observational estimate does not establish causality. Corticosteroids should remain limited to clear clinical indications. Prospective studies should capture indication, dose, duration, concurrent antibiotic use and pair-level data for matched analysis.