Resistance profiles of uropathogenic E. coli: ESBL and colistin in focus

Escherichia coli is among the most common causes of urinary tract infections (UTIs), and the rise in extended-spectrum beta-lactamase (ESBL)-producing isolates is a growing concern because of increasingly limited treatment options. This study aimed to investigate the resistance profiles of ESBL-positive and -negative uropathogenic E. coli isolates to antibiotics used in treatment and colistin.

Urine samples sent to the Central Laboratory of Istanbul University, Istanbul Faculty of Medicine, for routine examination between September 2023 and January 2024 were included in the study. The presence of ESBL and susceptibility to antibiotics other than colistin were determined by the Vitek2 (bioMérieux, France) automated system, and colistin susceptibility was determined by the reference broth microdilution method.

Of the 80 patients with E. coli, 80% were female, and 20% were male; 32.5% were children, and 67.5% were adults. All E. coli isolates were susceptible to nitrofurantoin, ertapenem, and meropenem. 40% of the strains were ESBL-positive. In respect of multidrug-resistant bacteria, among ESBL-positive and-negative isolates, 12.5% and 2.1% were resistant to six, 28.1% and 8.3% to five, 34.4% and 6.25% to four, and 18.75% and 16.7% to three different antibiotic groups, respectively. Of 80 E. coli strains, 92.5% of which were sensitive to colistin, the MIC50 value was 0.5 mg/L, and the MIC90 value was 2 mg/L.

Although the colistin resistance rate and minimum inhibitory concentration (MIC) values are not high, it is important to monitor resistance when treating problematic infections with multiple resistance.