Aims of study

1. Incidence of ciprofloxacin resistance in Escherichia coli isolates from urinary infections Antonia Poiată1, Ioana Bădicuț2, Cristina Tuchiluș1 1University of Medicine anf Pharmacy „Grigore T. Popa” Iasi, Microbiology Department 2University of Medicine anf Pharmacy „Carol Davila” Bucuresti, Microbiology Department Aims of study MATERIAL and METHODS This surveillance study was performed to determine the in vitro activity of ciprofloxacin against clinical isolates of Escherichia coli and to establish the incidence of resistance during a period of 20 years (between 1993 and 2013 respectively). • A total 1378 isolates were obtained from patients hospitalized with urinary tract infections. Complicated urinary tract infections are a common indication for the use of ciprofloxacin because they are often caused by E. coli resistant to other agents. • Susceptibility testing. Minimum inhibitory concentrations (MIC) were determined by the agar dilution method described in the National Committee for Clinical Laboratory Standards (NCCLS) and Clinical and Laboratory Standards Institute (CLSI). The susceptibilities were interpreted using the NCCLS breakpoints: bacterial strains exhibiting an MIC of ≤ 1 and ≥ 4 mg/L were regarded as susceptible and resistant to ciprofloxacin, respectively. RESULTS Table 1. Ciprofloxacin susceptibility of Escherichia coli cultured from the biological samples of hospitalised urological patients. The distribution of MIC values of ciprofloxacin for the E. coli investigated strains is shown in Table 1. The MICs ranged from 0.03 to 1 µg/mL during 1993-2002 period, from 0.125 to 16 µg/mL during 2003-2012 period, and from 0.06 to 16 µg/mL during 2013 year. In Table 2, the range of MICs, MIC 50, MIC 90 and susceptibility rates for ciprofloxacin are listed. During 1993-2002 period the 431 isolates of E. coli that were tested, 92.8% are inhibited by concentration of 0.125 µg/mL. All strains were susceptible. In 2003-2012 period MIC50 values were fourfold higher and MIC 90 fell into the resistant range for ciprofloxacin. This antimicrobial agent registered the similarly activity in terms of MIC 90 (4 µg/mL) for the 2003-2013 period. Following the breakpoint, the rates of resistance were 19% for 2003-2012 period and higher (27.5%) for 2013 year. The MIC distribution during 1993-2013 period illustrate that our MIC values is smaller than the median value of MICs 0.11 for 1993-2002 period, 1.8 for 2003-2012 period and 1.9 for 2013 year, respectively. The difference in the MIC 50 and median MIC varies from about two dilution steps for 1993-2002 period and about eight dilution step for 2003-2013 period. After 2002 year, aproximately 20% ofthe isolates were resistant to ciprofloxacin with MIC values that exceeded the breakpoints for susceptibility. In summary, the results of surveillance study revealed great differences in the prevalence of ciprofloxacin resistance ranging from 0% in the 1993 period to 27.5% in the 2013 year. This may be attributed to the frequent use of fluoroquinolones for the treatment of urinary infections. Continous monitoring of antibiotic resistance rates needs to be performed. Table 2. Comparative in vitro activity of ciprofloxacin against Escherichia coli strains isolated during 1993-2013 period. REFERENCES • National Committee for Clinical Laboratory Standards. Methods for dilution antimicrobial tests for bacteria that grow aerobically. Approved Standard M7-A5. National Committee for Clinical Laboratory Standard, Wayne, P. A., 2003 • Clinical and Laboratory Standards Institute. Performance standards for antimicrobial susceptibility testing. 23th informational supplement. 2014; CLSI M100-S20, Wayne, PA. • Hernandez JR, Martinez-Martinez L, Canton R, Coque TM, Pascual A, Spanish Group for Nosocomial Infections (GEIH). Nationwide study of Escherichia coli and Klebsiella pneumoniae producing extended-spectrum beta-lactamases in Spain. Antimicrob Agents Chemother. 2005; 49 (5); 2122-2125.