High trimethoprim-sulfamethoxazole resistance in ciprofloxacin-resistant Escherichia coli strains isolated from urinary tract infection

BACKGROUND: Escherichia colt is the most frequently isolated pathogen of urinary tract infections. Rising rates of resistance to antimicrobial agents among E. coli leads to limit treatment options for these infections. The aims of this study were to evaluate resistance patterns of uropathogenic E. coli against antimicrobial agents which can be used in healthcare for the treatment of UTI and to examine particularly an association between resistance to ciprofloxacin and trimethoprim sulfamethoxazole. METHODS: A total of 1123 E. coli strains were obtained consecutively from urine specimens in research and private hospital, during 2010-2011. Ampicillin, ceftazidime, ceftriaxone, cefazolin, ciprofioxacin, ertapenem, gentamicin, imipenem, nitrofurantoin, piperacillin-tazobactam and trimethoprim-sulfamethoxazole (TMS-SMX) resistance were determined by automated system. RESULTS: Among tested antibiotics, imipenem had the best efficient antibiotic against all E. coli strains (100%), followed by ertapenem (99.98%), amikacin (99.94%), and nitrofurantoin (99.91%). A statistically significant difference has been found for the resistance of non-ESBL and ESBL-producing E. coli strains against gentamicin, piperacilin-tazobactam, ciprofioxacin and TMP-SMX (P<0.001). 13.1% of strains were extended-spectrum beta-lactamase (ESBL) producers, 19.5% of strains were ciprofioxacin-resistant (CIP-R) and 34.6% of strains were TMS-SMX-resistant. TMP-SMX (63%) had the highest resistance among CIP-R urinary E. coli strains tested in this study. CONCLUSIONS: The findings of this study has indicated that there was a strong correlation between the occurrence of ESBL and the development of ciprofioxacin resistance. High resistance both ciprofioxacin and TMP-SMX and an association between resistance to these two antimicrobial agents in uropathogenic E. colt strains has not been previously reported and warrants further study.