Mobile genetic elements in Klebsiella pneumoniae

Abstract

Klebsiella pneumoniae is a clinically important pathogenic bacteria that poses a serious threat to human health. In particular, the emergence of hypervirulent and multidrug-resistant K. pneumoniae has posed great challenges in clinical anti-infective therapy. In the K. pneumoniae genome, mobile genetic elements (MGEs), such as plasmids, prophages, transposons, and insertion sequences, enhance bacterial viability and adaptation by mediating the horizontal transfer of virulence genes, antibiotic resistance genes, and other adaptive genes. This paper reviews the types and characteristics of the main MGEs in K. pneumoniae, focusing on their effects on bacterial virulence and antibiotic resistance, with the aim of providing clues for developing infection control measures and new antibacterial drugs.

Keywords: Klebsiella pneumoniae; antibiotic resistance; mobile genetic elements; virulence factors.

Fig 1

Virulence factors of hvKP. (a) Siderophores encoded by the virulence gene clusters ent, ybt, iuc, and iro on chromosomes and plasmids. (b) Colibactin can cause DNA damage in the host. (c) The cps and rmpA/rmpA2 gene clusters mediate the formation of the mucus phenotype by regulating the synthesis of the capsule. (d) The efflux pump maintains and enhances pathogenicity by expelling antimicrobial peptides. (e) LPS on cell membranes that regulate the immune response. (f) The protein secretion system interferes with the survival of host cells and surrounding bacteria by secreting toxic effector proteins. (g) Fimbriae on the surface of bacteria enhance bacterial adhesion (the figure is produced by Figdraw).

Fig 2

MGEs in K. pneumoniae and their transmission mechanisms. (a) Conjugative plasmid moves between bacteria by conjugative transfer. (b) The evolutionary mechanisms of CR-hvKP include the transfer or recombination of resistance plasmids and virulence plasmids. (c) IS and Tn move into bacterial chromosome and plasmid by encoding transposases. (d) Prophages integrate their own genome into bacterial chromosome and replicate with host DNA. (e) Bacteria recognize and cleave foreign DNA through the CRISPR-Cas system to resist plasmid and phage invasion. (f) Integrative conjugative element (ICE) integrates into the host genome by conjugation (the figure is produced by Figdraw).