Background
Klebsiella pneumoniae liver abscess (KPLA) with extrahepatic migratory infections is defined as invasive KPLA (IKPLA). The type VI secretion system (T6SS) is involved in the pathogenesis of KPLA. We hypothesized that T6SS play a role in the IKPLA.
Methods
16S rRNA gene sequencing was performed on abscess samples. Polymerase chain reaction (PCR) and reverse transcription (RT)-PCR was used to validate the expression difference of T6SS hallmark genes. In vitro and in vivo experiments were performed to identify the pathogenic feature of T6SS.
Results
PICRUSt2 predicted that the T6SS-related genes were notably enriched in the IKPLA group. PCR detection of T6SS hallmark genes (hcp, vgrG, and icmF) showed that 197 (81.1%) were T6SS-positive strains. The T6SS-positive strains detection rate of IKPLA group was higher than KPLA group (97.1% versus 78.4%; p < 0.05). RT-PCR showed that the hcp expression level was markedly increased in IKPLA isolates (p < 0.05). The T6SS-positive isolates showed higher survival against serum and neutrophil killing (all p < 0.05). The T6SS-positive Klebsiella pneumoniae infection mice had a shorter survival time, higher mortality and an increased interleukin (IL)-6 expression in the liver and lungs (all p < 0.05).
Conclusions
T6SS is an essential virulence factor for Klebsiella pneumoniae and contributes to the IKPLA.