β-lactmaes Genotypes Of Klebsiella Pneumoniae Isolates And Induction And Inhibition Of The β-lactamase Gene Expression

Objective:To investigate the predominant β-lactamase genotypes of Klebsiella pneumoniae isolates and carrying mode of the β-lactamase genotypes as well as to determine the primary action mechanism of antibiotic to induce or histidine kinase inhibitor to suppress the expression of β-lactamase genes.Methods:Both tube dilution method and E-test was used to detect the susceptibility of K.pneumoniae isolates to β-lactam antibiotics. The major β-lactamase genotypes in the β-lactam antibiotic-resistant isolates were detected by PCR and sequencing, while the β-lactamase activity of the isolates were examined by disk diffusion test. The effects of cefotaxime inducing the expression of β-lactamase genes and histidine kinase inhibitor closantel suppressing the expression up-regulation of cefotaxime-induced β-lactamase genes were determined by real-time fluorescent quantitative RT-PCR.Results:All the118P-lactam antibiotic-resistant K.pneumoniae isolates express β-lactamases, while90.7%(107/118) of the isolates were detectable for KPC-2, TEM-1, CTX-M-14, SHV-11and/or OXA-1genes, in which the positive rates of TEM-1(71.0%) and SHV-11(64.5%) were significantly higher than that of the other three β-lactamase genotypes (P<0.05).68.2%(73/107) of the resistant isolates possess two or more than two β-lactamase genotypes, in which the TEM-1+SHV-11(30.8%,33/107) acted as the predominant β-lactamase genotype carrying mode. Except for KPC-2-mRNA,1/4MIC cefotaxime could induce the significant elevation of TEM-1-, SHV-11-, CTX-M-14-or OXA-1-mRNA level (P<0.05), but the cefotaxime-induced mRNA level elevation could be inhibited by100μmol/L closantel (P<0.05).Conclusion:TEM-1and SHV-11are the major β-lactamase genotypes carried by the K.pneumoniae isolates from Zhejiang area, and TEM-1plus SHV-11(TEM-l+SHV-11) is the predominant carrying mode of the β-lactamase genotypes. Sublethal dose of cefotaxime can induce the expression up-regulation of P-lactamase genes of K.pneumoniae. The histidine kinase inhibitor, closantel, can block the cefotaxime-induced expression up-regulation of K.pneumoniae P-lactamase genes.