Study on the resistance mechanism of an isolate of Klebsiella pneumoniae resistant to 3 kinds of carbopenems

doi:10.3969/j.issn.1673-8640.2014.04.016

Abstract

Abstract:

Objective　To investigate the resistance mechanism of an isolate of Klebsiella pneumoniae（K30） resistant to carbopenems. Methods　Minimum inhibition concentrations（MIC） of Klebsiella pneumoniae K30 to 13 antibiotics were determined by agar dilution method. Modified Hodge test was used to detect carbopenems. Class A carbopenem（KPC）， Class B carbopenem（NDM, IMP, VIM and SIM）， extended spectrum beta-lactamases [ESBLs（CTX, TEM and SHV）]， AmpC beta-lactamases [Amp C（FOX, EBC, ACC, DHA, CIT and MOX）] and Class Ⅰ integron were amplified by polymerase chain reaction（PCR）. Real-time fluorescence quantitation PCR was carried out to investigate the mRNA expression levels of porin genes（ompK35 and ompK36）. Plasmid conjugation experiment was subjected to reveal the transferability of Klebsiella pneumoniae K30 resistant genes. Results　The antimicrobial susceptibility test showed that Klebsiella pneumoniae K30 was resistant to 11 antibiotics， but kept intermediary to cefoxitin sodium and susceptible to amikacin. Modified Hodge test was positive in Klebsiella pneumoniae K30. Class A carbopenem KPC gene and 2 ESBLs CTX and SHV genes were positive by PCR amplification. The genes were conformed as KPC-2, CTX-M3 and SHV-38 by sequencing and comparing in GenBank. No other resistance gene Class Ⅰ integron was detected. The porin gene ompK35 and ompK36 expression levels did not decrease comparing with those of Klebsiella pneumoniae（ATCC 700603）. Plasmid conjugation experiment was failed in the study. Conclusions　The main resistance mechanism of the isolate of Klebsiella pneumoniae resistant to carbopenems might be associated with the combined producing KPC-2 and ESBLs， and KPC-2 may be not mediated by plasmid.

Key words: Carbopemen, Class Ⅰ integron, Porin, Plasmid conjugation experiment, Klebsiella pneumoniae

CLC Number:

R446.5

XIE Chunbao, YU Hua, XIAO Daiwen, YANG Yongchang, JIANG Wei, LIU Hua, HUANG Wenfang.. Study on the resistance mechanism of an isolate of Klebsiella pneumoniae resistant to 3 kinds of carbopenems[J]. , 2014, 29(4): 369-374.

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