Higher Virulence Renders K2 Klebsiella pneumoniae a Stable Share Among Those from Pyogenic Liver Abscess

Objective: To explore why serotype K2 accounts for a stable share in Klebsiella pneumoniae from pyogenic liver abscess (PLA). Methods: Totally 15 K2 K. pneumoniae strains from PLA, 21 K2 from non-PLA, and 31 K1 from PLA were collected from China. Sequence typing, molecular serotyping, regular PCR, and Galleria mellonella lethality were performed. A total of 12 virulence genes were detected: peg-344, allS, p-rmpA, p-rmpA2, c-rmpA, fimH, mrkD, iucA, iroN, irp2, entB, and wzi. The differences between K2 K. pneumoniae strains from PLA and non-PLA were investigated along with K1 ones. Results: Significant differences were found between K2 strains from PLA and non-PLA for the rates of virulence genespeg-344 and iucA. The latter group also showed more diverse sequence types than the former. Significant differences were only found for virulence genes allS and irp2 between K1 and K2 strains from PLA. Based on the equal virulence factors backgrounds other than serotypes, K2 strain is more virulent than K1 as G. mellonella lethality confirmed. Gene p-rmpA only brings equal virulence to p-rmpA plus p-rmpA2 in K2 strain. Conclusion: Based on the same virulence factors backgrounds except serotypes, K2 K. pneumoniae is more virulent than K1 from PLA, which provides a survival advantage to maintain a stable share.