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. 2025 Apr;53(2):667-678.
doi: 10.1007/s15010-024-02456-x. Epub 2025 Feb 3.

The type VI secretion system as a potential predictor of subsequent bloodstream infection of carbapenem-resistant Klebsiella pneumoniae strains on intestinal colonization

Chenfeng Zhao #  1 , Pingjuan Liu #  1 , Xiaoshu Lin #  1 , Chenyu Wan  1 , Kang Liao  1 , Penghao Guo  1 , Jiankai Deng  1 , Zhongwen Wu  1 , Yaqin Peng  1 , Junqi Huang  2   3   4   5 , Yili Chen  6
Affiliations

The type VI secretion system as a potential predictor of subsequent bloodstream infection of carbapenem-resistant Klebsiella pneumoniae strains on intestinal colonization

Chenfeng Zhao et al. Infection. 2025 Apr.

Abstract

Background: The type VI secretion system (T6SS) has been recognized as a novel virulence factor in Klebsiella pneumoniae. This study investigated the occurrence of T6SS genes in carbapenem-resistant Klebsiella pneumoniae (CRKP) strains during intestinal colonization and evaluated their effect on the development of bloodstream infections.

Methods: The study encompassed 2,385 patients admitted to the intensive care unit (ICU) and subjected to routine screening for intestinal colonization with CRKP. PFGE was employed on CRKP strains isolated from both the patients' intestine and blood cultures, confirming their genetic similarity. PCR was employed to detect the presence of carbapenemase genes, T6SS genes, and virulence genes. Quantitative real-time PCR was conducted to assess the expression levels of the core genes associated with the T6SS. The correlation between T6SS expression and sBSI was further investigated.

Results: Approximately 10% (238/2385) of ICU patients tested positive for CRKP colonization. Among patients who tested positive, 10.1% (24/238) developed CRKP-sBSI. Patients carrying T6SS-positive CRKP isolates were more commonly linked to a history of invasive procedures, antibiotic use, and immunosuppression (P < 0.05), and were strongly associated with 28-day mortality (P < 0.001). It indicated that T6SS-positive CRKP strains exhibited a higher prevalence of virulence genes, such as rmpA and iucA, compared to T6SS-negative ones (P < 0.001). Compared to the strains isolated from simple colonization group, there was a significant increase in the mRNA expression of both hcp and vgrG genes (P < 0.05) of strains from the sBSI group, suggesting the key genes of the T6SS may play a significant role in the occurrence and progression of sBSI caused by CRKP.

Conclusion: The presence of the T6SS in a CRKP strain from intestinal colonization can serve as a promising predictive marker for sBSI. Conducting screenings for CRKP in patients' intestinal flora and monitoring T6SS carriage can improve the prevention and management of CRKP bloodstream infections.

Keywords: Active screening; Carbapenem-resistant Klebsiella pneumoniae; Intestinal Colonization; Subsequent Bloodstream Infection; Type VI secretion system.

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Conflict of interest statement

Declarations. Ethics approval and consent to participate: This study was approved by the Institutional Review Board and Ethics Committee of The First Affiliated Hospital of Sun Yat-sen University and conducted according to the Declaration of Helsinki(Approved No. of ethics committee: [2024]-200). The ethics committee approved the waiver of informed consent owing to the retrospective nature of the review. All research data were de-identified and anonymously analyzed. Consent for publication: NA. Competing interests: The authors declare no competing interests.

Figures

Fig. 1
Fig. 1
Flow chart of this study
Fig. 2
Fig. 2
The relationship between the timing of active screening for CRKP positivity in the intestine and the length of stay in the ICU
Fig. 3
Fig. 3
The proportion of carbapenemase genotypes in different CRKPs strains
Fig. 4
Fig. 4
PFGE cluster analysis and typing characteristics of fourty-eight CRKP strains (24 cases). (Strain ID: “S” represents isolation from stool specimens, and “B” represents isolation from blood.)
Fig. 5
Fig. 5
The mRNA expression of T6SS genes between sBSI group and simple colonization group. **: P<0.001
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References

    1. Hu F, Wang M, Zhu D, et al. CHINET efforts to control antimicrobial resistance in China. J Glob Antimicrob Resist. 2020;21:76–7. - PubMed
    1. Guerra MES, Destro G, Vieira B, Lima AS, Ferraz LFC, Hakansson AP, Darrieux M, Converso TR. Klebsiella pneumoniae Biofilms and Their Role in Disease Pathogenesis [J]. Front Cell Infect Microbiol. 2022;12:638399. - PMC - PubMed
    1. Hu F, Pan Y, Li H et al. Carbapenem-resistant Klebsiella pneumoniae capsular types, antibiotic resistance and virulence factors in China: a longitudinal, multi-centre study. Nat Microbiol, 9, 814–29. - PMC - PubMed
    1. Humphries R, Bobenchik AM, Hindler JA, Schuetz AN. Overview of Changes to the Clinical and Laboratory Standards Institute Performance Standards for Antimicrobial Susceptibility Testing, M100, 31st Edition [J]. J Clin Microbiol. 2021;59(12):e0021321. - PMC - PubMed
    1. Zhang H, Han J, Wang Z, et al. Research progress on pathogenesis, antimicrobial resistance mechanism, and treatment of hypervirulent Klebsiella pneumoniae. Chin J Pathogen Biology. 2024;19(10):1239–43. 10.13350/j.cjpb.241025.

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