Evaluation of Prevalence of Trimethoprim Resistance Genes in Gram Negative Bacilli Isolated from Clinical Specimens of Patients Admitted to the Pars Hospital, Tehran

Trimethoprim is a bacteriostatic and broad-spectrum antibiotic used to treat infections, particularly urinary tract infections. Among dfrA genes, five genes including dfrA5, dfrA1, dfrA12, dfrA7 and dfrA17 are more important for resistance to trimethoprim. The aim of this study was to evaluate the frequency of encoding trimethoprim resistance genes in clinical specimens isolated from patients hospitalized in the pars Hospital, Tehran, Iran. Two hundred fifty clinical specimens including sputum, blood, body fluid, wound, urine and secrations were cultured on blood agar and EMB. After incubation at 37৹C for 24 hours, conventional biochemical tests were used to isolate and identify gram negative bacteria. Then, antibiotic susceptibility test was performed by disk diffusion agar method according to Clinical and Laboratory Standards Institute (CLSI 2020) guideline. Genomic DNA of trimethoprim resistant bacteria was extracted and polymerase chain reaction (PCR) was performed to detect the resistance genes. Hundred gram negative bacteria including Escherichia coli (42%), Pseudomonas (15%), Klebsiella (24%) and Acinetobacter (19%) isolated from clinical specimens. Based on the PCR results, dfr1 gene followed by dfr5 and dfr17, was the most frequent among trimethoprim resistant gram negative bacteria. The presence of dfr genes plays an important role in antibiotic resistance to trimethoprim