ABSTRACT
Objective@#To establish a Galleria mellonella model of liver abscess-related Klebsiella pneumoniae (K.pneumoniae) infection and to evaluate its feasibility for virulence detection.@*Methods@#Twelve liver abscess-related K. pneumoniae strains were collected in Wuxi No.2 People′s Hospital from January 2016 to December 2017. Twenty K. pneumoniae strains isolated from sputum and urine samples were used as classic strains. All isolates were analyzed by String test. Common capsular serotypes (K1, K2, K5, K16, K20, K54 and K57) of highly virulent K. pneumoniae strains were detected by PCR. Virulence test was performed to measure 80% lethal doses (LD80) of different serotypes in the same time period and the lethal time for 80% of larvae (LT80) at the same concentration.@*Results@#The 12 strains of liver abscess-related K. pneumoniae belonged to five serotypes, which were K1 (41.7%, 5/12), K2 (8.3%, 1/12), K5 (8.3%, 1/12), K20 (8.3%, 1/12) and K57 (33.4%, 4/12). High-virulence serotypes were not detected in the classic group. The positive rates of String test in the liver abscess group and the classic group were 75% and 10% (2/20), respectively. Results of the virulence test showed that when the concentration ranged from 1×105 CFU/ml to 1×108 CFU/ml, the lethal effects of different strains on Galleria mellonella larvae were in a concentration dependent manner. Twelve hours after infection, the numbers of dead larvae in K1 and K57 serotype groups were significantly higher than those in K2, K5, K20 and classic groups. The LD80 values of the liver abscess group at 96 hours after infection were as follows: 1×106 CFU/ml (K1, K57) and 1×107 CFU/ml (K2, K5, K20).@*Conclusion@#The liver abscess-related K. pneumoniae isolates are all highly virulent strains. The virulence of K. pneumoniae can be detected at 12 hours after infection of Galleria mellonella.
ABSTRACT
Objective To investigate the distribution of hypervirulent capsular serotypes and virulence genes of Klebsiella pneumoniae associated with pyogenic liver abscess(PLA),and analyze the homology of strains.Methods Twelve strains of liver abscess-related Klebsiella pneumoniae were isolated in Wuxi Second People's Hospital during January 2016 and August 2017.Among them,five were also detected in blood samples.All the strains were performed the viscous thread test,and the hypervirulent capsular serotypes and main virulence genes were detected by PCR.The homology of the strains was analyzed by the multilocus sequence types(MLST) and pulsed-field gel electrophoresis(PFGE).Results The positive rate of the viscous thread test for 12 strains of liver abscess-related Klebsiella pneumoniae was 75％.Three kinds of hypervirulent capsular serotypes,including K1 (6/12,50％),K54(1/12,8.3％) and K57(5/12,41.7％),were detected.The positive rates of virulence genes,such as wcaG,rmpA,ureA,fimH,mrkD,uge,Aer and iroNB,were all 100％,while that of iucB was 83.3％.The cf29a gene was not found,and the magA,allS and kfuBC genes were only detected in K1 serotype strains.MLST found that ST23(4/12,33.3％) and ST25(3/12,25％) were main sequence types,and then were ST412(2/12,16.7％),ST1660(1/12,8.3％),ST1049(1/t2,8.3％) and ST11 (1/12,8.3％).PFGE showed that 12 strains of Klebsiella pneumoniae were divided into 8 types,and that only 3 strains of K1 serotype belong to the same clonotype.Conclusion All the isolated liver abscess-related Klebsiella pneumoniae strains are highly virulent.ST23 and ST25 are main sequence types,and ST1049 is first reported.PFGE results show genetic diversity,and Kl-type Klebsiella pneumoniae has a certain epidemic tendency.