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Prevalence of blaCTX-M gene in multi-resistant Escherichia coli isolated from Urinary Tract Infections, Tehran, Iran

Mehdi Goudarzi, Fattaneh Sabzehali, Zahra Tayebi, Mehdi Azad, Shahram Boromandi, Ali Hashemi, Sima Sadat Seyedjavadi





The emergence and increase in the incidence of Extended-spectrum beta lactamase (ESBL) producing Escherichia coli has become an emerging challenge especially in hospitalized patients with UTI. The aim of the present study was to survey the frequency of bla CTX-M genotype in ESBL producing E. coli isolated from hospitalized patients with UTI and determination of their antibiotic resistance pattern.

Material and methods

A total of 135 E. coli isolates were collected from isolated from patients with UTI. The isolates were subjected to confirmatory phenotype tests for the presence of ESBL. 75 E. coli isolates were confirmed as ESBL-positive by means of the Double disc synergy test. In vitro susceptibility of ESBL isolates to 15 antimicrobial agents amoxicillin, penicillin, ceftazidime, cefotaxime, cefoxitin, ceftriaxone, cefixime, cephalexin, co-trimoxazole, gentamicin, nalidixic acid, ciprofloxacin, nitrofourantoin, amikacin and imipenem was performed by Kirby-Bauer’s Disk diffusion method according to Clinical and Laboratory Standards Institute (CLSI, 2012) guideline. PCR method was used to identify bla CTX-M gene in 75 ESBL positive strains.


PCR and sequence analysis showed that 75 (55.5%) isolates produced bla CTX-M genes. In vitro susceptibility of ESBL producing E. coli showed that all of them were resistant to amoxicillin and penicillin and The rates of resistance to the majority of tested antibiotics varied between 61% to 100 %, with the exception of amikacin (14.7%) and imipenem (2.7%). Our results showed that the frequency of bla CTX-M was strikingly high (93.3%).


These data confirmed that the frequency of bla CTX-M genes were high among E. coli isolated from patients with UTI. The trend of multidrug-resistant profile has been associated with bla CTX-M gene is alarming. Therefore, it is very important to establish a routine screening of ESBL in clinical isolates to prevent dissemination of resistant isolates in health care settings.


ESBL; Beta lactamase; Escherichia coli; antimicrobial resistance


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DOI: https://doi.org/10.22037/nbm.v2i4.6776