Antimicrobial susceptibility of clinical Escherichia coli isolates from uncomplicated cystitis in women over a 1-year period in Spain

Abstract

High usage of antibiotics in Spain has led to an increase in resistance in urinary Escherichia coli isolates in different geographic regions. The problem of resistance in urinary E. coli in Spain was investigated by gathering a large number of isolates from 20 different sites nationwide over a 1-year period from November 2003 to October 2004 in a large population of women. The objectives of this study were to assess the resistance to the antibiotics most commonly prescribed for community-acquired urinary tract infections (UTIs), according to age and different geographical areas of Spain, and to evaluate the potential association between geographical differences in quinolone consumption and resistance to E. coli. A total of 2,292 valid E. coli strains from female outpatients were isolated and sent to a single central reference laboratory for confirmation and susceptibility testing. Of these, 2,230 isolates were available for the age analysis. A two-sided chi2 test was used to identify differences in resistance between age groups. Antibiotic units per province were purchased from IMS and consumption was expressed in units per 1,000 people per year. Univariate correlation (Pearson coefficient) between resistance to ciprofloxacin and quinolone consumption was calculated using a two-sided p-value. Resistance shown by E. coli was more common to ampicillin (52.1%) and cotrimoxazole (26%), followed by quinolones (18%), whereas resistance to amoxicillin-clavulanic acid, cefuroxime-axetil and fosfomycin was less than 3%. In the subgroup of women aged >65 years, resistance to ciprofloxacin was 29% compared to 13% for the subgroup of women <65 years (p<0.001). For these same subgroups, resistance rates were 32% vs. 23% for cotrimoxazole (p<0.001) and 56% vs. 50% for ampicillin (p=0.02), respectively. Statistically significant correlations were found between consumption of quinolones and E. coli resistance to ciprofloxacin (r=0.5; p=0.025). Resistance of E. coli isolates to quinolones varied significantly according to geographical areas, ranging from a high of 16.5% and 16.6% in the southern and eastern regions of Spain, respectively, to a low of 8% in the north in women aged <65 years. Additionally, the susceptibility to quinolones of E. coli isolates recovered from women aged >65 years was significantly lower across all regions of Spain than that of isolates recovered from younger women. Fosfomycin, amoxicillin/clavulanic acid and cefuroxime-axetil are the most suitable antibiotics for empirical treatment in Spain given the high 18% and 26% resistance rates to quinolones and cotrimoxazole, respectively. Higher resistance rates to ciprofloxacin were associated with being aged 65 years and over. These data need to be considered when recommending empirical therapy for acute cystitis.