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Aim and Background:Today, the presence of broad-spectrum beta-lactamases in bacteria isolated from patients who express multiple drug resistance is a major health problem in most countries.
 Materials and Methods:A total of 346 samples of different clinical strains of enterobacteriaceae were isolated from Kahooresten. To determine the resistance of the samples, an antibiotic test was performed. Finally, ESBL isolates were tested by PCR for TEM, CTX-M, and SHV genes.
Results:Of the 346 isolates studied, 162 isolates of Klebsiella and 132 isolates of Escherichia coli were resistant to ceftazidime antibotic or cefotaxime, or both. Also, 82 (42.26%) were isolates producing ESBL.
Conclusions:Due to the high percentage of resistance to third-generation cephalosporins, accurate antibiotic testing before antibiotics is required in infections caused by ESBL-producing organisms.

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Aim and Background:
Extended-spectrum beta-lactamase of CTX-M type is considered as an Important mechanism resistant to beta-lactamases in gram- negative pathogen and is widely increasing.  Klebsiella pneumoniae species are able to produce extended-spectrum beta- lactamase (ESBLs). The aim of this study was to detect the prevalence of CTX-M gene in ESBLs produsing Klebsiella pneumoniae isolated form patients in different  region of TEHRAN city from December2016 to july 2017 by using PCR method.
Material and methods:
In this analytical- descriptive study antibacterial susceptibility patterns of 176 Klebsiella pneumoniae tested to Cefepime, Ampicillin, Gentamicin, Amikacin, Cefalotine, Ceftazidime, Piperacillin, Ciprofloxacin, Imipenem, Cefotaxime , Nitrofurantoin, Trimethoprim using disk diffusion method. In addition, confirmatory test for detecting ESBLs phenotypes was performed using Cefotaxim-Clavulanic acid combination disk. The presence of CTX-M  gene was assessed by using PCR.
Results:
Confirmatory phenotypic test showed 56.81% of the isolates were ESBL positive. The prevalence of CTX-M gene in isolated Klebsiella pneumoniae was 28%. In this study, the highest resistance was observed for ampicillin antibiotics (24.88%) and the least resistance to antibiotic imipenem (6.06).
Conclusion:
High frequency of CTX-M gene in ESBL produsing isolates indicates  that this enzyms plays an important role in resistance to beta lactam containing anti biotics. Therefore, proper infection control tools and appropriate therapeutic approaches in different parts of the hospitals are necessary to prevent their release.