assessment of ampc beta-lactamase genes among clinical escherichia coli isolates

background :   ampc beta lactamases play a significant role in creating resistance to third generation cephalosporins worldwide. they mostly express on chromosome of enterobacteriaceae especially escherichia coli and cause consequential problem in clinical treatment and lead to failure in diagnosis and phenotypic test recommended by clinical and laboratory standards institute.   methods : totally 200 e. coli isolates from different hospitals of tehran were collected. the isolates were screened by disk diffusion method according to the clsi guidelines. the profiles and prevalence surveys of ampc ( dha , citm , mox and fox -type) β-lactamase genes in clinical isolates of e. coli by phenotypic and molecular methods.   results :    out of 200 e. coli isolated, 115 (89.8%) and 13 (10.2%) isolates were identified as esbl- and ampc- beta-lactamase producers, respectively. among ampc producers, 13 (100%) and 5 (38.5%) isolates was reported by pcr assay as blacitm and dha , respectively. mox and fox genes were not detected in any sample. conclusion :   our results highlight the importance of using molecular detection methods to identify β-lactamase-producer that have resistance to antibiotics.