Frequency of AmpC β-lactamase Resistance in Escherichia coli Isolates from Urinary Tract Infections in Gorgan, Iran

AmpC β-lactamases are among the most important cephalosporinases. Production of AmpC βlactamases in microorganisms is often associated with multidrug resistance and limited treatment options. This study aimed to determine antimicrobial susceptibility pattern and frequency of AmpC β-lactamase genes in Escherichia coli strains isolated from urinary tract infections. Materials and Methods: The study included 154 E. coli isolates from urine samples of patients in medical centers of Gorgan, Iran. Cefoxitin-resistance was evaluated by the KirbyBauer method. Cefoxitin-resistant strains were evaluated using cefoxitin disks alone and combined with boronic acid to confirm production of AmpC β-lactamase. Presence of MOX gene was investigated by polymerase chain reaction. Results: Among the 154 E. coli isolates, 37 (24%) were cefoxitin-resistant, 16 of which were found to be AmpC βlactamase-positive in the phenotypic test. In addition, the MOX gene was found in two isolates. Conclusions: The frequency of AmpC β-lactamase-producing E. coli and MOX gene in Gorgan is close to the regional and national