title: Phenotypic and Molecular Characterization of Extended-Spectrum β-Lactamase Produced by Escherichia coli, and Klebsiella pneumoniae Isolates in an Educational Hospital.
abstract: BACKGROUND
  Extended-spectrum beta-lactamases (ESBLs) are a group of enzymes that hydrolyze antibiotics, including those containing new cephalosporins, and they are found in a significant percentage of Escherichia coli and Klebsiella pneumoniae strains. With the widespread use of antibiotics, difficulties with infection therapy caused by drug resistant organisms, especially those that have acquired resistance to beta-lactams, such as broad-spectrum cephalosporins, have amplified the above-mentioned organisms.
  
  
  OBJECTIVE
  This study was conducted to characterize ESBLs among E. coli and K. pneumonia isolates by molecular and phenotypic methods.
  
  
  METHODS
  Different strains of E. coli and K. pneumonia were collected from patients with urinary tract infections. The ESBL phenotype was determined by a double disk diffusion test (DDDT). In addition, polymerase chain reaction (PCR) analysis specific for β-lactamase genes of the TEM and SHV family was carried out. The PCR products were run on agarose and examined for DNA bands.
  
  
  RESULTS
  A total of 245 E. coli and 55 K. pneumonia strains were isolated from different samples. In total, 128 of the 300 isolates were confirmed as potential ESBLs producers as follows: 107 (43.67%) E. coli and 21 (38.18%) K. pneumonia. ESBLs genes were found in 24 isolates (18.75%): 21 E. coli and 3 K. pneumonia isolates. The TEM gene was present in 13 (12.14%) E. coli strains, but it was not detected in K. pneumonia. In addition, the SHV gene was present in 8 (7.47%) E. coli and 3 (14.28%) K. pneumonia isolates. Five (4.67%) of the E. coli isolates harbored both TEM and SHV genes. All isolates (100%) were susceptible to imipenem. The lowest rates of resistance to other antibiotics were observed for; piperacillin-tazobactam (6.25%), amikacin (12.5%) and gentamicin (14.84%). The rates of resistance to other antibiotics were as follow: nitrofurantoin (16.4%), nalidixic acid (23.43), co-trimoxazole (25%), cefepime (32%), ciprofloxacin (55.46%), ampicillin (69.53%), ceftazidime (100%), and cefotaxime (100%).
  
  
  CONCLUSIONS
  The results of this study indicate the widespread prevalence of ESBLs and multiple antibiotic resistance in E. coli and K. pneumoniae. Therefore, beta-lactam antibiotics and beta-lactamase inhibitors or carbapenems should be prescribed based on an antibacterial susceptibility test.
authors: Department of Microbiology and Immunology, Cellular and Molecular Research center, Faculty of Medicine, Shahrekord University of Medical Sciences, Shahrekord, IR Iran.
authors: Abolfazl
authors: A
authors: Gholipour
authors: Department of Pathology, Al-Zahra Hospital, Isfahan University of Medical Sciences, Isfahan, IR Iran.
authors: Neda
authors: N
authors: Soleimani
authors: Nosocomial Infection Research Center, Isfahan University of Medical Sciences, Isfahan, IR Iran.
authors: Dariush
authors: D
authors: Shokri
authors: Department of Microbiology, Al-Zahra Hospital, Isfahan University of Medical Sciences, Isfahan, IR Iran.
authors: Sina
authors: S
authors: Mobasherizadeh
authors: Department of Pathology, Al-Zahra Hospital, Isfahan University of Medical Sciences, Isfahan, IR Iran.
authors: Mohammad
authors: M
authors: Kardi
authors: Department of Pathology, Al-Zahra Hospital, Isfahan University of Medical Sciences, Isfahan, IR Iran.
authors: Azar
authors: A
authors: Baradaran
keywords: Escherichia coli; Klebsiella pneumonia; Molecular; Phenotypic; extended-spectrum β-lactamase (ESBL)
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