Comparison of risk factors for, and prevalence of, antibiotic resistance in contaminating and pathogenic urinary Escherichia coli in children in primary care: prospective cohort study.

Background: All-cause antibiotic prescribing affects bowel flora antimicrobial susceptibility, and may increase risk of urinary autoinoculation with antibiotic-resistant microbes. However, little is known about relative prevalence of, or risk factors for, antimicrobial resistance among potentially pathogenic microbes thought to be contaminating and infecting urine.

Methods: Secondary analysis of 824 children under 5 years of age consulting in primary care for an acute illness and their Escherichia coli isolates cultured at ≥103 cfu/mL from the Diagnosis of Urinary Tract infection in Young children (DUTY) study. Multivariable logistic regression investigating risk factors for resistance to amoxicillin, co-amoxiclav, cefalexin, ciprofloxacin, trimethoprim, nitrofurantoin and cefpodoxime in microbes meeting the laboratory criteria for urinary tract infection: 'pathogens' (>105 cfu/mL, n = 79) and 'contaminants' (103 to 105 cfu/mL, n = 745).

Results: Forty-three percent of E. coli were resistant to at least one tested antibiotic, with resistance highest to amoxicillin (49.37% pathogenic versus 37.32% contaminant, P = 0.04), trimethoprim (27.85% versus 16.52%, P = 0.01) and co-amoxiclav (16.46% versus 21.48%, P = 0.30). Multidrug resistance (to ≥3 antibiotic groups) was present in 17.07% of pathogens and 30.13% of contaminants (P = 0.04). No isolates were resistant to nitrofurantoin. Recent (0-3 months) exposure to antibiotics was associated with resistance in both pathogens (aOR: 1.10, 95% CI: 1.01-4.39) and contaminants (1.69, 1.09-2.67).

Conclusions: Prevalence of resistance (including multidrug) was high, but there was no consistent relationship between isolate pathogen/contamination status and resistance. Recent all-cause antibiotic prescribing increased the probability of antimicrobial resistance in both pathogenic and contaminating urinary E. coli in children in primary care.