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.

Background: Septic pulmonary embolism (SPE) is an associated complication of Klebsiella pneumoniae liver abscess (KPLA). However, previous studies have reported that its incidence varies widely. We conducted a systematic review and meta-analysis to investigate the incidence of SPE in patients with KPLA. We further analyzed their clinical and computed tomography (CT) features. Methods: Two researchers reviewed PubMed, EMBASE, Web of Science, and Cochrane Library databases to identify the articles that reported SPE in patients with KPLA. The search was conducted from the date of establishment of each database up to January 2021. After screening the articles and extracting the data, we used Review Manager 5.3 for analysis and processing. Results: We selected six articles that included 1,158 patients with KPLA. Of these, 70 patients had SPE. The pooled incidence of SPE was 6% (95% confidence interval, 3%–9%). Among patients with SPE, 85% were men, 72% had diabetes, and 52% displayed the feeding vessel sign on the chest CT. The mortality rate was 12%. Quality assessment revealed that half of the included studies had a high quality. Conclusion: The pooled incidence of SPE in patients with KPLA was 6%. Men and patients with diabetes were more prone to SPE. For patients with KPLA who had SPE as an associated complication, the mortality rate was approximately 12%.