Impact of antibiotic usage on resistance in microorganisms; Urinary tract infections with E-coli as a case in point

Objectives: In this study, we sought to establish a correlation between consumption of flouoroquinolones in our hospital and the emergence of ofloxacin resistant strains of E.coli in the urinary specimens. Data of all urinary samples, received at Aga Khan University Hospital between January 1995 and December 2002, was retrieved and analyzed. Specimens yielding E-coli as an isolate were included in this study. Methods: E. coli Isolates showing >103 colonies were identified using standard microbiological techniques. Antibiotic susceptibility of E-coli was tested using Kirby Bauer disc diffusion method. Antimicrobial usage data, obtained through hospital Pharmacy as unit utilized per year for Quinolones in different medical and surgical units was available only for the period of 1997-2002. Results: Among 32,722 urinary specimens E.coli (53%) was the most frequent isolate. Steady increase in the number of ofloxacin resistant E.coli was noted, 24% in 1995 to 55% in 2002. Maximum quinolone resistant E coli have been observed in Medical units, 41% in 1997 increasing to 70% in 2002, followed by Surgery units (35% to 54%) and Pediatrics (12 to 38%). Sharp increase in ofloxacin consumption in our hospital, 1997 (28613 units) to 2002 (96880 units) has been observed. Trends in quinolone resistance correlate significantly with utilization in the same period as shown by linear regression. Conclusion: E- coli resistance against most antibiotics has been on a rise particularly for quinolones. The utilization of quinolones correlates with increasing resistance in our hospitalized patients.