Genotypes ofβ-lactamase in Klebsiella pneumoniae isolates and induction and inhibition of theβ-lac-tamase gene expression / 中华微生物学和免疫学杂志

ABSTRACT

Objective To investigate the predominant genotypes of β-lactamase in Klebsiella pneu-moniae isolates and the mechanism of antibiotic and histidine kinase inhibitor in affecting β-lactamase gene expression .Methods Tube dilution method and E-test were used to detect the susceptibility of K.pneumon-iae isolates to β-lactam antibiotics .The major genotypes of β-lactamase in β-lactam antibiotic-resistant iso-lates were identified by PCR and sequencing method .Disk diffusion test was performed to analyze the activity ofβ-lactamase .The effects of cefotaxime and histidine kinase inhibitor closantel on the expression of β-lac-tamase gene were evaluated by real-time fluorescent quantitative RT-PCR.Results All of the 118 β-lactam antibiotic-resistant K.pneumoniae isolates expressed β-lactamase, 90.7%(107/118) of which were KPC-2, TEM-1, CTX-M-14, SHV-11 and/or OXA-1 gene positive.The positive rates of TEM-1 (71.0%) and SHV-11 (64.5%) were significantly higher than that of the other three genotypes ( P<0.05).68.2%(73/107) of the isolates possessed two or more than two β-lactamase genotypes, and 30.8%(33/107) iso-lates were identified as TEM-1+SHV-11 genotype.Except for KPC-2 mRNA, the levels of TEM-1, SHV-11, CTX-M-14 and OXA-1 mRNA were significantly up-regulated by cefotaxime at MIC/4 (P<0.05), but were inhibited by 100μmol/L closantel (P<0.05).Conclusion TEM-1 and SHV-11 are the majorβ-lactamase genotypes carried by K.pneumoniae strains isolated from Zhejiang area , and TEM-1 plus SHV-11 ( TEM-1+SHV-11) is the predominant carrying mode of the β-lactamase genotypes .Sublethal dose of cefotaxime can enhance the expression of β-lactamase genes in K.pneumoniae, while the histidine kinase inhibitor , closan-tel, can block the increased expression of β-lactamase genes induced by cefotaxime .