Frequency of extended-spectrum beta-lactamase genes and antibiotic resistance patterns of Gram-negative bacteria in Iran: A multicenter study

Background: Extended-spectrum b-lactamase (ESBL) producing bacteria are growing in number worldwide and cause complications in antibiotic therapy for patients, thus raising mortality and morbidity. Aim: This study aims to (a) determine the frequency rate of ESBL-producing gram-negative bacteria that were collected using phenotypical and molecular methods from nine cities in Iran and (b) extract their antibiotic susceptibility patterns. Materials and methods: P. aeruginosa, A. baumannii, E. coli, K. pneumoniae, and Enterobacter spp. were collected from nine cities in Iran in one year. The 3rd-generation cephalosporin-resistant strains were identified through antibiotic susceptibility testing. ESBL-producing bacteria were identified by the double disk method in line with CLSI guidelines, and the most common ESBL genes were identified by PCR assay in phenotypical ESBL positive strains. Results: Data derived from a total of 4083 consecutive clinical samples were included in this study. Out of 1275 isolates resistant to one of the 3rd-generation cephalosporins, 475 were ESBL strains (12%). TEM was the most common ESBL gene found in phenotypic positive strains. Conclusion: This study shows the existence of ESBL-producing bacteria in the setting under study. It is noted here that carbapenems and aminoglycoside remain the best treatment to the ESBL-producing gram-negative bacteria.