A molecular study of aac(3)- IIa (aacC2) gene in aminoglycoside resistant Escherichia coli isolated from urine

Escherichia coli is the most prevalent etiologic agent of urinary tract infections which is the cause of about 80% of cases. Enzymatic inactivation of aminoglycosides by aminoglycoside-modifying enzymes is the main mechanism of resistance to these antibiotics in Escherichia coli. The aim of this study was the detection of aac(3)-IIa gene among aminoglycoside resistant clinical isolates of E. coli using PCR method. After collection of 250 clinical isolates of E. coli, antibiotic susceptibility patterns of isolates were determined by disk diffusion method for gentamicin, amikacin, tobramycin, kanamycin and netilmicin by considering the CLSI principles. Chromosomal and plasmid DNA of the isolates were extracted using DNA extraction Kits and PCR method was used for detection of the aac(3)-IIa gene. Results show that 96% of E. coli isolates were resistant to tobramycin, 90% resistant to kanamycin, 82% resistant to gentamicin, 30% resistant to netilmicin and 8% resistant to amikacin. aac(3)-IIa gene was detected in 54.83% of E. coli isolates. Because of high prevalence of resistance toward aminoglycoside antibiotics which is due to its transfer among bacteria by transferable elements such as transposons and plasmids. Therefor, tracing transfer routs among different bacteria is very important.