The Association Between Genetic Variants in Extended Spectrum Beta-Lactamases and AmpC-producing Gram-Negative Bacilli and Antibiotic Resistance

 A large group of genes associated with extended-spectrum beta-lactamases (ESBL) and AmpC expression is involved in inducing antibiotic resistance in various bacteria. Identifying these genes and assessing their harboring will be crucial in determining the pattern of antibiotic resistance. This study aimed to characterize genetic variants in extended-spectrum beta-lactamases, AmpC-producing gram-negative bacilli, and associated antibiotic resistance.

 This cross-sectional research was conducted on clinical samples of patients admitted to Rasool-e-Akram Hospital, Tehran, Iran (2019 and 2020). The genetic variants were assessed by the Polymerase chain reaction method. The pattern of durability to antibiotics was determined by the disk diffusion system.

Of the 80 isolates that produced ESBL and AmpC beta-lactamase, 75 cases were ESBL producers and 5 cases co-producers of ESBL and AmpC. The most common cultivated strains included Escherichia coli (61.2%) and Klebsiella pneumoniae (31.3%). The highest antibiotic resistance in ESBL producers was related to cefotaxime, trimethoprim-sulfamethoxazole, and cefazolin, and the lowest resistance level was related to colistin, cefoxitin, and ceftriaxone. The total frequencies of common genes of ESBL-producing gram-negative bacilli were blaCTX-M (76.0%), blaTEM (46.7%), and blaSHV (26.7%), while multigenic harboring was also observed in 49.3%. The level of drug resistance to Imipenem, Amikacin, and Ceftazidime in people who harbored the blaSHV gene was significantly higher than in other cases.

The most common cultivated strains included E. coli and K. pneumoniae. blaCTX-M, blaTEM, blaSHV, and multigenic expression were observed. The detection of the blaSHV gene is associated with increased antibiotic resistance to Imipenem, Amikacin, and Ceftazidime.