Serum-induced iron-acquisition systems and TonB contribute to virulence in Klebsiella pneumoniae causing primary pyogenic liver abscess.
BACKGROUND
Klebsiella pneumoniae has become the predominant pathogen causing primary pyogenic liver abscess (PLA).


METHODS
K. pneumoniae was stimulated by human serum, and gene expression was analyzed by microarray.


RESULTS
Three putative iron acquisition systems, Yersinia high-pathogenicity island (HPI), iucABCDiutA, and iroA(iroNDCB), that increased in expression and predominated in PLA-associated K. pneumoniae strains were identified. By use of siderophore uptake assays, these 3 systems were confirmed to be siderophore-dependent iron acquisition systems. Only the irp2-iuc-iroA triple mutant showed decreased virulence in mice. Full-genome analysis of K. pneumoniae strain NTUH-K2044 identified 10 putative iron uptake systems. Seven of these 10 systems were TonB dependent, including Yersinia HPI, iucABCDiutA, and iroA. A tonB deletion mutant was demonstrated to have profound attenuation of virulence. Immunization with the tonB mutant resulted in seroconversion of extracellular polysaccharide antibodies and protective efficacy against subsequent exposure to the parental strain.


CONCLUSIONS
Iron uptake systems were the genes in K. pneumoniae that were highly up-regulated in response to sera. Although there are multiple iron transporter systems in NTUH-K2044, a mutation in all 3 loci (irp2, iuc, and iroA) is necessary to decrease virulence. The tonB mutant is a potential vaccine candidate because it can induce a significant protective immune response against challenge with a wild-type strain.
Hsieh
Pei-Fang
PF
Department of Microbiology, National Taiwan University College of Medicine, Taipei, Taiwan.
Lin
Tzu-Lung
TL
Lee
Cha-Ze
CZ
Tsai
Shih-Feng
SF
Wang
Jin-Town
JT
D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001693:Biological Transport, Active; D002352:Carrier Proteins / Q000378:metabolism; D005260:Female; D017353:Gene Deletion; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D006801:Humans; D007501:Iron / Q000378:metabolism*; D007710:Klebsiella Infections / Q000382:microbiology*; D007711:Klebsiella pneumoniae / Q000145:classification / Q000235:genetics / Q000472:pathogenicity*; D046290:Liver Abscess, Pyogenic / Q000382:microbiology*; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D005810:Multigene Family; D009154:Mutation; D044967:Serum; D014158:Transcription, Genetic; D014774:Virulence
D001426:Bacterial Proteins; D002352:Carrier Proteins; D008565:Membrane Proteins; C057616:tonB protein, Bacteria; D007501:Iron