Hong Kong Med J 2011;17(Suppl 2):S21-3
Antimicrobial resistance among uropathogens causing cystitis in women
PL Ho, KY Yuen, RMK Lam, KM Kam
Department of Microbiology, The University of Hong Kong, Hong Kong
1. Among Escherichia coli from adult women with acute cystitis, the rates of antimicrobial resistance were 52.8% for ampicillin, 29.5% for co-trimoxazole, and 12.9% for ciprofloxacin. Nitrofurantoin and fosfomycin remain active against >90% of the isolates.
2. The respective age-stratified rates for co-trimoxazole and ciprofloxacin resistance were 26.4% and 9.6% for women aged 18-50 years, and 35.5% and 19.4% for women aged ≥51 years. Being aged ≥51 years (Odds ratio [OR]=2.3, 95% confidence interval [CI]=1.1-4.8, P=0.02) and receipt of recent antibiotic treatment (OR=2.5, 95% CI=1.1-5.8, P=0.03) were significantly associated with fluoroquinolone resistance.
3. Ampicillin and co-trimoxazole should not be used as first-line agents for empirical treatment of acute cystitis. As fluoroquinolone resistance was less than 10% among isolates obtained from younger women, these agents are still useful for empirical treatment. Nonetheless, the high rates of fluoroquinolone resistance among women who were older or who had received antibiotic treatment recently indicates the need to consider alternatives such as nitrofurantoin, fosfomycin and amoxicillin-clavulanate as initial therapy.
4. Molecular analysis of the multidrug resistant strains showed that they were genetically diverse, with no evidence of epidemic strains. Nonetheless, resistant strains possess virulence traits distinct from susceptible isolates, suggesting that they may evolve from other sources and not by acquisition of resistance mutations in susceptible isolates from humans.