Abstract:

Objective To investigate the virulence gene distribution and clinical molecular characteristics of Klebsiella pneumoniae. Methods Totally，158 non-duplicate clinical isolates of Klebsiella pneumoniae were collected from the Second Affiliated Hospital of Nanchang University from January 2016 to March 2017. Automatic drug susceptibility analyzer was used to identify the isolates and determine drug susceptibility in vitro. The high virulence Klebsiella pneumoniae（hvKP）was screened by string test. The virulence genes and drug resistance genes of Klebsiella pneumoniae and 5 common capsule serotypes were determined by polymerase chain reaction（PCR）. Multi-locus sequence typing（MLST）and homology analysis were performed. The clinical data of infected patients were collected，and the clinical characteristics of patients infected with carbapenem-resistant Klebsiella pneumoniae（CRKP）and common antibiotics sensitive Klebsiella pneumoniae（SKP）were compared. Results Among the 158 isolates of Klebsiella pneumoniae，22 isolates（13.9%）were CRKP，and 29 isolates（18.4%）were SKP. All CRKP isolates were multi-drug resistant，all of them expressed carbapenem resistance gene bla_KPC-2，and one isolate also carried metalloenzyme carbapenem resistance gene bla_IMP-4. The results of string test showed that among 51 isolates of Klebsiella pneumoniae with bloodstream infection，13 were hvKP，2 were CRKP，and 11 were SKP. The determination rates of uge，iutA，mrkD，alls and aerobactin genes in SKP were higher than those of CRKP，and the determination rate of ybtA gene was higher（P<0.05）. Capsule serotyping results showed that K1 and K2 had 4 isolates each，and K57 had 1 isolate，all of which were SKP. No common capsule serotypes were determined in CRKP. MLST results showed that the 51 CRKP and SKP isolates were dominated by ST11 type（24/51），22 CRKP isolates were all ST11 type，and the SKP capsule serotypes were ST23（4 isolates），ST11（2 isolates）and ST65（2 isolates）. Homology analysis showed that 21 of 51 isolates of CRKP and SKP had homology>70%，among which type A（5 isolates），type B（9 isolates）and type C（3 isolates）were ST11 CRKP，and 4 isolates of ST23 SKP were type D. Invasive procedures，use of carbapenems and prognosis of patients with CRKP and SKP infection were statistically significant（P<0.05），but there was no statistical significance in age，sex，underlying diseases and department distribution（P>0.05）. Conclusions The Klebsiella pneumoniae virulence genes（ybtA，uge，mrkD，alls，iutA and aerobactin）could be used as virulence markers of hvKP. The drug resistance genes of CRKP isolates are complex and diverse，and the prognosis of patients infected with CRKP is poor，so it is recommended to conduct CRKP medical screening as soon as possible.

Key words: Bloodstream infection, Klebsiella pneumoniae, Virulence gene, Multi-locus sequence typing, Clinical characteristic