Galleria mellonella infection model for evaluating the virulence of Klebsiella pneumoniae

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. Key words: Klebsiella pneumoniae; Capsular serotype; Virulence; String test; Galleria mellonella