Antimicrobial Resistance in Urinary Isolates of Escherichia coli with Special Reference to Fluoroquinolone Resistance and Extended Spectrum Beta-Lactamase (ESBL) Production

BACKGROUND The commonest bacterial agent involved in causation of urinary tract infection (UTI) is Escherichia coli, both in the community as well as in the hospital. In this study Escherichia coli strains isolated from patients with UTI were studied especially for extended spectrum beta-lactamase (ESBL) production and determination of fluoroquinolone resistance. METHODS This descriptive study was conducted in the Department of Microbiology, Katihar Medical College and Hospital from December 2018 to May 2020. Urine samples from suspected UTI cases were processed and bacterial isolates were identified as per standard protocol. Antimicrobial susceptibility testing was done by Kirby-Bauer discdiffusion method on Mueller-Hinton agar. ESBL detection was done as per Clinical and Laboratory Standards Institute (CLSI) guidelines. RESULTS Out of 3938 urine samples received in the microbiology laboratory, 708 samples showed significant growth of various bacteria and candida species, out of these only 105 patients had urinary tract infection caused by Escherichia coli. The male to female ratio was 0.25:1. Isolates were highly sensitive to nitrofurantoin (80.9 %) followed by amikacin (72.4 %) and imipenem (71.5 %). Maximum resistance was seen with amoxicillin (98.1 %), cefuroxime (96.2 %), cefpodoxime and cefotaxime (90.5 %), ceftriaxone (85.7 %), nalidixic acid (91.4 %) and ciprofloxacin (70.5 %). 70.5 % were found to be ESBL producers and 29.5 % were non-ESBL producers. The double disc synergy test (DDST) could detect only 42.8 % of ESBL producers whereas phenotypic confirmatory disc diffusion (PCDDT) detected 70.5 % of ESBL producers. CONCLUSIONS It was seen in the present study that a high proportion of community acquired strains of Escherichia coli were ESBL producers. In this study, 70.5 % of Escherichia coli strains were ESBL positive. It can therefore be recommended that all gram-negative isolates be tested for ESBL production preferably by the PCDDT test as this test was found to be most sensitive for detection of ESBL production. The PCDDT test requires minimum laboratory infrastructure, is cheap and easy as compared to molecular methods. KEY WORDS Escherichia coli, UTI, ESBL, PCDDT, DDST