The Type VI Secretion System Contributes to the Invasiveness of Liver Abscess Caused by Klebsiella pneumoniae

Abstract

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.

Identification of a novel CG307 sub-clade in third-generation-cephalosporin-resistant Klebsiella pneumoniae causing invasive infections in the USA

“…Additionally, relative to cluster 1, cluster 2 strains had a distinct set of effector/immunity proteins from a T6SS (). T6SSs function as injection machinery that can directly puncture both eukaryotic and prokaryotic membranes, and have been identified as contributing to K. pneumoniae pulmonary infection, gastrointestinal colonization, bacterial competition and liver abscess formation [72–75]. Future work will be necessary to further functionally characterize potential differences in virulence and resistance factors contributing to each CG307 clades’ respective success.…”

Genomic and transcriptomic characteristics of type VI secretion system inKlebsiella pneumoniae

“…Thus, these three proteins have dual roles, serving as both components and substrates of the T6SS (5)(6)(7). Therefore, due to the crucial roles played by these genes in the T6SS, many studies utilize hcp and vgrG genes as markers to identify the presence or absence of the T6SS cluster (8,9) . The primary function of T6SS involves interbacterial antagonism encompassing both interspecies and intraspecies competition (10,11).…”