Comparison of minimum inhibitory concentration values for fluoroquinolones against Escherichia coli causing urinary tract infection in both hospitalized patients and outpatients

To determine the resistance among Escherichia coli isolates causing urinary tract infections in hospitalized patients and outpatients. This study was carried out in the Department of Microbiology, Dokuz Eylul University, Medical Faculty Hospital, Inciralti, Ismir, Turkey, from February 1997 through to June 1998. A total of 300 Escherichia coli strains were isolated from urine specimens of 111 hospitalized and 189 elderly outpatients (more than 20 years of age). We determined the minimum inhibitory concentrations of the test drugs nalidixic acid, pefloxacin, ofloxacin, norfloxacin and ciprofloxacin by the microdilution method, recommended by the National Committee for Clinical Laboratory Standards. Minimum inhibitory concentrations(50) and minimum inhibitory concentrations(90) values of strains tested against fluoroquinolones, pefloxacin and nalidixic acid were the same for strains isolated from hospitalized and outpatients (0.125 microg/ml outpatients (0.03 microg/ml). Twenty-six (9%) of 300 Escherichia coli strains were resistant to all drugs used. Twenty (77%) of these 26 strains were isolated from hospitalized patients. We found that the resistance to nalidixic acid is much higher than other fluoroquinolones. At the same time, the resistance in the strains that were isolated from hospitalized patients is again higher than outpatient strains (46%). Resistance among Escherichia coli isolates from patients to quinolones used in the treatment of urinary tract infections was rare during this period. Our study, like many other reports showed the increased resistance to fluoroquinolones for clinical isolates. However the appearance of multi resistant clones and the elevated prevalence of quinolones resistance in the hospital studied are warning signals for an increase in resistant strains as seen in many other countries. Therefore, it is important for physicians to use fluoroquinolones carefully so as to prevent, or delay, the emergence of resistant strains.