Detection on AmpC b-lactamases and AmpC gene of Acinetobacter baumannii

Objective To detect AmpC b-lactamases and ampC gene of 45 strains Acinetobacter baumannii and study the status of drug resistance of the AmpC-producing bacillus.Methods b-lactamases of the 45 strains was extracted by ultrasonic crushing,and AmpC b-lactamases was examined by Cefoxitin in three dimensional test.The total DNA of the 45 Acinetobacter baumannii was extracted,and AmpC gene was amplified by polymerase chain reaction(PCR).The drug resistance was analysed by MIC method.Results There were 11 strains with three-dimensional test and PCR detection of ampC gene were both positive.These 11 strains were confirmed to be AmpC-producing strains.There was no significant difference(χ2=3.500,P0.05) in the detection rate between three-dimensional test method and PCR method.Detecting rate of the genotypes of AmpCβ-lactamases were ACT(4.4%)with 1 strain,FOX,DHA,CMY-G1,CMY-G2.Amikacin(90.9%) was the highest sensitive of the AmpC-producing strains,followed by imipenem(54.5%).AmpC-producing strains had high resistance rate,especially for Ampicillin,Aztreonam,Ceftriaxone,Aefotetan,Cefazolin,Nitrofurantoin and Ceftazidime reached 100%.Resistance rate of AmpC-producing strains was significantly higher than no AmpC-producing strains.Conclusion There is no significant difference in the detection rate between three-dimensional test method and PCR method,but there are high false positive rate and high false negative rate.This study can show the serious situation of drug resistance in AmpC-producing strains,and suggest ot use clinical medicine carefully.