Study on the relatedness of homology of carbapenem-resistant Klebsiella pneumoniae using MALDI-TOF MS

Abstract

Objective To evaluate the ability of Matrix-assisted laser desorption ionization-time of flight mass spectrum (MALDI-TOF MS) on homology analysis of carbapenem-resistant Klebsiella pneumoniae(Carbapenemase-Resistant K. pneumoniae, CRKp). Methods During January 2017 to December 2017, a total of 57 strains isolatedfromChanghai Hospital, Shanghai and 36 strainsfrom Urumqi First Hospital, Xinjiang were included for retrospective study. Inclusion criteria: strains which resistant to one of the carbapenems and with more than 100 peaks in identification mass spectrum. A total of 39 isolates were selected and divided into three groups according to the PFGE typing results: (1) Highly homologous group (17 strains with blaOXA-48 gene); (2) Moderate homology group (16 strains with blaKPC gene); (3)The non-homology group (8 strains with other resistance mechanisms). Mass spectrometry results were analyzed using BioNumeric and the two classification methods in SARAMIS, respectively.The PFGE analysis results were regarded as standard when evaluate the reliability of the other three analytical methods. Results Forhighly homologous group, the analysisresults of KA-A type dientical mass by two classification methods in SARAMIS were accord with PFGE,and the identity mass value is>80%, the similarity is>85%. However, for non-homologous group, the identity mass value is<80%, the similarity is<85% when compared with PFGE, which indicated that the method based on MALDI-TOF MS was not premium for this group of strains. For moderate homologous strains,the results of two SARAMIS methods for KC-A type havepoor consistency with PFGE, for the identity mass value is<70%, the similarity is<90%. Conclusions Based on MALDI-TOF MS using BioNumeric software and SARAMIS database software could be regarded as a screening method for phylogenetic analysis among CRKp strains with high homology. While, it should not be applied to evaluate homology of the strains with genetic diversity for lacking stability. Key words: Klebsiella pneumoniae; Carbapenems; Drug resistance, bacterial; Spectrometry, mass, matrix-assisted Laser desorption-ionization; Electrophoresis, gel, pulsed-field