On detection of plasmid-mediated AmpC β-lactamase and genotype in Klebsiella pneumoniae

Objective:To explore the formation of ESBL and AmpC β-Lactamase of K.pneumoniae in lower respiratory tract infections,and AmpC β-Lactamase genotypic resistance.Methods:Microbiological identification was performed with the VITEK 60 System and ESBLs were detected in accordance with the confirmatory test recommended by NCCLS.Suspected positive strains of AmpC β-lactamase were screened with cefoxitin disk diffusion.The genotypes were analyzed by cefoxitin three-dimensional test,conjugation test and PCR sequencing.Results:Of the 97 isolates,33(34.02%)were ESBLs positive,16(16.49%) were screened to be AmpC β-lactamase positive,of which 9(9.28%)were confirmed through the three-dimensional test.From them,9 conjugants were produced by conjugation,and confirmed to be much the same as the original phenotype by PCR sequencing.They were all ESBLs positive and no isolates of being only AmpC β-lactamase positive were detected.Among them,7 were DHA and 2 were CIT.Conclusion:K.pneumoniae isolated from lower respiratory tract has higher productivity of ESBLs and AmpC β-Lactamase and AmpC β-Lactamase is mainly of DHA genotype.The production of AmpC β-Lactamase and AmpC β-Lactamase is main reason for K.pneumoniae to be resistant to drugs.