Aims of study 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). 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 period, from to 16 µg/mL during 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 period the 431 isolates of E. coli that were tested, 92.8% are inhibited by concentration of µg/mL. All strains were susceptible. In 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 period. Following the breakpoint, the rates of resistance were 19% for period and higher (27.5%) for 2013 year. The MIC distribution during period illustrate that our MIC values is smaller than the median value of MICs 0.11 for period, 1.8 for period and 1.9 for 2013 year, respectively. The difference in the MIC 50 and median MIC varies from about two dilution steps for period and about eight dilution step for period. After 2002 year, aproximately 20% ofthe isolates were resistant to ciprofloxacin with MIC values that exceeded the breakpoints for susceptibility. 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. Incidence of ciprofloxacin resistance in Escherichia coli isolates from urinary infections Antonia Poiată 1, Ioana Bădicuț 2, Cristina Tuchiluș 1 1University of Medicine anf Pharmacy „Grigore T. Popa” Iasi, Microbiology Department 2University of Medicine anf Pharmacy „Carol Davila” Bucuresti, Microbiology Department MATERIAL and METHODS RESULTS 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. REFERENCES 1.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., Clinical and Laboratory Standards Institute. Performance standards for antimicrobial susceptibility testing. 23 th informational supplement. 2014; CLSI M100-S20, Wayne, PA. 3.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); Period Cumulative percentage of strains inhibited at the stated concentration (µg/mL) n= n= n=541 Table 1. Ciprofloxacin susceptibility of Escherichia coli cultured from the biological samples of hospitalised urological patients. PeriodMIC rangeMIC 50MIC 90Susceptible Median value of strains (%)MIC Table 2. Comparative in vitro activity of ciprofloxacin against Escherichia coli strains isolated during period.