Frequency of Various Types of Beta-Lactamase Enzymes in Escherichia coli Strains Isolated From Urine Samples in Aliabad, North-east of Iran

Beta-lactam resistance is rising in gram-negative bacilli. The aim of this study was to assess the frequency of β-lactamase enzymes, including extended-spectrum β-lactamases (ESBLs), metallo-β-lactamase (MBL), and AmpC beta-lactamase in Escherichia coli isolated from urine samples of the patients referred to medical laboratories in Aliabad.

A total of 780 urine samples were collected from patients suspected of having urinary tract infection (UTI). In positive urine samples, E. coli strains were identified by biochemical tests. The antibiotic resistance pattern was determined by disk diffusion method and phenotypic confirmatory test was performed for detecting ESBLs, MBL and AmpC beta-lactamases producers.

Out of 780 urine samples, 250 E. coli strains were isolated from the positive samples. The majority of the isolates (more than 90%) were resistant to ampicillin and amoxicillin. However, imipenem was an effective antibiotic among the isolates. The frequency of the ESBLs, MBL and AmpC beta-lactamases producers were determined to be 40%, 16.8%, and 30%, respectively.

In this study, the high frequency of MBL and AmpC beta-lactamases may suggest an increasing trend of resistance to cephalosporins and carbapenems. This could have a great impact on the management of UTI cases in and out of hospital. It seems that continuous monitoring is highly essential in detecting resistant cases.