Abstract: To analyse the prevalent characterization of aminoglycosides modifying enzymes in rmtB-positive Escherichia coli from pig farms. The polymerase chain reaction (PCR), restriction fragment length polymorphism (RFLP) and DNA sequencing were used to detect and identify the resistant genes encoding aminoglycoside modifying enzymes. Micro-dilution method was adopted to evaluate the MICs to 10 aminoglycosides. Total of 7 aminoglycoside modifying enzymes were presented in 48 rmtB-positive Escherichia coli from pig farms.And the present ratio of aac(3)-II, aph(3′)-II, aph(3′)-VII, aadA1, aac(6′)-Ib, aac(3)-IV and aph(4)-I were 85.8%, 77.6%, 77.6%, 34.7%, 14.3%, 10.2% and 8.2% by turn.The resistant ratio of the 48 rmtB-positive Escherichia coli to Kanamycin, Amikacin, Gentamycin, Tobramycin, Sisomicin, Netilmicin, Neomycin, Streptomycin, Spectinomycin and Apramycin were 100%, 100%, 100%, 100%, 100%, 100%, 79.2%, 77.1%, 89.6% and 27.1% respectively. The highest coincidence was 98% between the phenotypes to aminoglycosides and genotype of AMEs. It indicated that aminoglycoside modifying enzymes were prevalent in rmtB-positive Escherichia coli. They mediated the resistance of Escherichia coli to aminoglycosides with 16S rRNA methylase-RmtB.

Key words: Escherichia coli; aminoglycosides modifying enzymes (AMEs); resistance; RmtB