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Escherichia coli (E. coli) is one of the most common hospital infections in which the emergence of antibiotic resistance and the prevalence of Extended Spectrum Beta-Lactamase (ESBL) are considered major problems in the control of hospital infections. The aim of this study was to investigate the frequency of blaCTX-M, blaTEM, and blaSHV beta-lactamase genes in E. coli isolated from different clinical samples by the combined disk and multiplex PCR methods. E. coli isolates from different clinical samples were collected over six months and identified with the help of standard microbiological and biochemical tests. The antibiotic resistance of E. coli isolates was determined by the disk diffusion method. The production of beta-lactamases was evaluated by the combined disk method, and the presence of blaCTX-M, blaTEM, and blaSHV genes was assessed by the multiplex PCR method. From the total of 200 examined samples, 114 E. coli isolates (57%) were identified with the highest resistance to ceftazidime, amikacin, cefotaxime, and tetracycline (100%) and the lowest resistance to imipenem (3.5%) and ampicillin (14%). 58 isolates (50.88%) were ESBL positive by phenotypic test, of which 20 isolates (34.48%) contained the blaTEM gene and 15 isolates (25.86%) contained the blaCTX-M gene. No positive blaSHV gene was observed in the samples. The presence of beta-lactamase genes examined in this study along with the occurrence of antibiotic resistance indicates the spread of bacterial resistance in the study area and shows the importance of rational antibiotic treatment. [ABSTRACT FROM AUTHOR]

Beta-lactamases are the most common cause of bacterial resistance to beta-lactam antibiotics. AmpC-type beta-lactamases hydrolyze cephalosporins, penicillins, and cephamycins. Therefore, the study aims was to determine antibiotic resistance and to investigate the presence of AmpC beta-lactamase gene in clinical strains of Escherichia coli isolated from hospitalized patients in Tabriz. In this cross-sectional descriptive study, 289 E. coli specimens were collected from clinical specimens. Disk diffusion method and combined disk method were used to determine the phenotype of extended spectrum β-Lactamase producing (ESBLs) strains. Then PCR was used to evaluate the presence of AmpC (FOX) betalactamase gene in the strains confirmed in phenotypic tests. Antibiotic resistance was also determined using disk diffusion by the Kibry-Bauer method. A total of 121 isolates were identified as generators of beta-lactamase genes. 72 (59.5 %) isolates producing ESBL and 49 (40.5 %) isolates were identified as AmpC generators. In the PCR test, 31 isolates contained the FOX gene. The highest resistance was related to the antibiotics amoxicillin (76.12%), ceftazidime (70.24%) and nalidixic acid (65.05%). The results indicate an increase in the prevalence of betalactamase genes and increased resistance to beta-lactam antibiotics, which can be the result of improper use of antibiotics and not using antibiotic susceptibility tests before starting treatment. Also, using phenotypic and molecular diagnostic methods such as PCR together can be very useful. [ABSTRACT FROM AUTHOR]