Antimicrobial susceptibility pattern of extended‑spectrum β‑lactamase‑producing bacteria causing nosocomial urinary tract infections in an Iranian referral teaching hospital
Volume 3, Issue 1, Winter 2014, Pages 6-11
. Rasool Soltani, . Mohsen Ehsanpoor, . Farzin Khorvash, . Dariush Shokri
Abstract Objective: Gram‑negative bacilli are the most important cause of nosocomial urinary
tract infections (UTIs). The production of extended‑spectrum β‑lactamase (ESBL) enzymes
is a common mechanism of resistance among these bacteria. The aim of this study was to
determine the rate of ESBL producing Gram‑negative bacteria causing nosocomial UTI in a
referral hospital as well as their susceptibility pattern to the most commonly used antibiotics.
Methods: In a prospective cross‑sectional study performed over a 6‑month period, urinary
specimens obtained from hospitalized patients with documented culture‑proved nosocomial
UTI (age range of 1-87 years). Isolated aerobic Gram‑negative bacteria underwent further
microbiologic tests for detection of ESBL, as well as antimicrobial susceptibility test using
Kirby-Bauer (disk diffusion) and E‑test methods.
Findings: During the study period, 213 urine samples were detected to have growth of
Gram‑negative organism. Escherichia coli was the most frequently isolated organism (61%).
ESBL was detected in 102 isolates including 38.5% of E. coli, 39.5% of Klebsiella pneumonia,
88.5% of Pseudomonas aeruginosa, and 100% of Acinetobacter baumannii strains. Imipenem
and meropenem were the most effective antibiotics on E. coli and K. pneumoniae strains. P.
aeruginosa and A. baumannii strains showed high resistance to all tested antibiotics.
Conclusion: Large numbers of Gram‑negative bacteria causing nosocomial UTIs produce
ESBL with most being multidrug‑resistant. Therefore, routine ESBL detection testing and
subsequent antibiogram with disk diffusion method could be useful to determine the best
treatment options for UTI.