Abstract:

Objective To study the molecular characteristics and virulence of hypermucoviscous carbapenem-resistant Klebsiella pneumoniae（HM-CRKP），and to provide a reference for clinical research and infection control.Methods The 1 825 isolates of carbapenem-resistant Klebsiella pneumoniae（CRKP） were isolated from inpatients of Xinhua Hospital，Shanghai Jiao Tong University School of Medicine from January 2009 to December 2020，and the string test was used to screen for HM-CRKP. The serotypes of HM-CRKP isolates were identified by capsular wzi genotyping. The 6 major carbapenemase genes（bla_KPC，bla_NDM，bla_IMP，bla_VIM，bla_GES and bla_OXA-48） and 4 virulence genes（rmpA2，iucA，rmpA and iroN） were identified by polymerase chain reaction（PCR）. The virulence of isolates were determined by Galleria mellonella larvae infection model.Results Totally，96 isolates of HM-CRKP were screened from 1 825 isolates of CRKP. The determination rate of HM-CRKP had been increasing since the first determination in 2015，reached 12.2% in 2020. The total determination rate of HM-CRKP was 5.3%. Carbapenemase genes were determined in 95 isolates of HM-CRKP，including bla_KPC-2，bla_KPC-3，bla_NDM-1 and bla_IMP-4，and bla_KPC-2 was found to be the most predominant（89.6%，86/96）. The bla_KPC-2 and bla_IMP-4 were found in 1 isolate，and 9 different capsular wzi serotypes were found in HM-CRKP，of which wzi64 was the dominant serotype（82.3%，79/96）. The 69.8% of HM-CRKP carried rmpA2 and iucA，59.4% of HM-CRKP carried rmpA and iroN. According to the distribution of virulence genes（rmpA2，iucA，rmpA and iroN），HM-CRKP could be classified into 3 modes. The 59.4% of the isolates were belonged to mode Ⅰ（rmpA2，iucA，rmpA and iroN were determined simultaneously）；the 10.4% of the isolates were belonged to mode Ⅱ（rmpA2 and iucA were determined simultaneously）；the 30.2% of the isolates were belonged to mode Ⅲ（rmpA2，iucA，rmpA and iroN were not determined）. The virulence of HM-CRKP isolates was different from each other in Galleria mellonella larvae model，but there was no statistical significance in virulence among HM-CRKP isolates with different virulence gene modes（P>0.05）.Conclusions The bla_KPC-2 carried wzi64 is the main HM-CRKP collected from Xinhua Hospital，Shanghai Jiao Tong University School of Medicine，and the determination rate of HM-CRKP is increasing year by year. The virulence of HM-CRKP is different from each other，while there is no significant virulence difference of HM-CRKP with different virulence gene modes.

Key words: Klebsiella pneumoniae, Carbapenem resistance, Hypermucoviscous, bla_KPC-2, wzi64, Virulence