Study On The Distribution Of Aminoglycoside Modifying Enzymes Among ESBLs-producing Escherichia Coli

ObjectiveTo investigate the distribution of aminoglycoside modifying enzymes among ESBLs producing Escherichia coli.MethodsTo17isolates of ESBLs-producing E. coli, susceptibility test was performed using K-B method. PCR method was used to detect the genes for aminoglycoside-modifying enzymes such as aac(3)-Ⅰ, aac(3)-Ⅱ, aac(6’)-Ⅰ b, aac(6’)-Ⅱ, ant(3")-Ⅰ and ant(2")-I in those17strains producing ESBLs. Sequencing analysis of the PCR product were performed by ABI3730sequencing anlysis system, and the sequences were analyzed by blast method. ResultsThe resistance rate to getamycin and tobramycin were100and52.9%, respectively. The resistance rate to ciprofloxacin and levofloxaxin were both88.2%. The most genotype for aminoglycoside-modifying enzymes was aac(3)-Ⅱ(94.1%), the second was aac(6’)-Ⅰ b(35.3%). The positive rates of aac(3")-Ⅰ and ant(2")-Ⅰ were11.8%and5.9%respectively. One strain was resistant to aminoglycoside on phenotype, without those genes however.4strains were classical on genotype, one with aac(6’)-Ⅰb-Cr, the another one with a new subtype among the6strains of E.coli with aac(6)Ⅰ b.ConclusionPositive rate for aac(3)-Ⅱ takes the first place, followed by aac(6’)-Ⅰ b among the genes for aminoglycoside-modifying enzymes. There exist at least3sub-types of aac(6’)-Ⅰ b, one kind of gene for aminoglycoside-modifying enzymes in strains of E.coli. Among those sub-types, the classical type is the main, accompanied by aac(6’)-Ⅰ b-Cr and its new sub-type.