title: Identification of a capsular variant and characterization of capsular acetylation in Klebsiella pneumoniae PLA-associated type K57.
abstract: Klebsiella pneumoniae can cause community-acquired pyogenic liver abscess (PLA). Capsular polysaccharide (CPS) is important for its virulence. Among 79 capsular (K) types discovered thus far, K57 is often associated with PLA. Here, we report the identification of a K57 variant. Cps gene locus sequencing revealed differences between the K57 reference strain 4425/51 (Ref-K57) and a variant, the PLA isolate A1142. While Ref-K57 cps contained orf13 encoding a putative acetyltransferase, the insertion of a putative transposase-encoding gene at this position was detected in A1142. This variation was detected in other K57 clinical strains. Biochemical analyses indicated that A1142 was deficient in CPS acetylation. Genetic replacement and complementation verified that orf13 was responsible for CPS acetylation. Acetylation increased CPS immunoreactivity to antiserum and enhanced K. pneumoniae induction of pro-inflammatory cytokines through JNK and MAPK signaling. While acetylation diminished the serum resistance of bacteria, it promoted adhesion to intestinal epithelial cells possibly via increasing production of type I fimbriae. In conclusion, acetylation-mediated capsular variation in K57 was observed. Capsular acetylation contributed to the variety and antigenic diversity of CPS, influenced its biological activities, and was involved in K. pneumoniae-host interactions. These findings have implications for vaccine design and pathogenicity of K. pneumoniae.
authors.affiliation: Department of Microbiology, National Taiwan University College of Medicine, Taipei, Taiwan.|Department of Medical Research, E-Da Hospital, Kaohsiung, Taiwan.|School of Medicine, I-Shou University, Kaohsiung, Taiwan.
authors.forename: Chun-Ru
authors.initials: CR
authors.lastname: Hsu
authors.affiliation: Department of Internal Medicine, Far Eastern Memorial Hospital, New Taipei City, Taiwan.
authors.forename: Chun-Hsing
authors.initials: CH
authors.lastname: Liao
authors.affiliation: Department of Microbiology, National Taiwan University College of Medicine, Taipei, Taiwan.
authors.forename: Tzu-Lung
authors.initials: TL
authors.lastname: Lin
authors.affiliation: Department of Microbiology, National Taiwan University College of Medicine, Taipei, Taiwan.
authors.forename: Han-Ru
authors.initials: HR
authors.lastname: Yang
authors.affiliation: Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan.
authors.forename: Feng-Ling
authors.initials: FL
authors.lastname: Yang
authors.affiliation: Department of Microbiology, National Taiwan University College of Medicine, Taipei, Taiwan.
authors.forename: Pei-Fang
authors.initials: PF
authors.lastname: Hsieh
authors.affiliation: Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan.
authors.forename: Shih-Hsiung
authors.initials: SH
authors.lastname: Wu
authors.affiliation: Department of Microbiology, National Taiwan University College of Medicine, Taipei, Taiwan.|Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan.
authors.forename: Jin-Town
authors.initials: JT
authors.lastname: Wang
mesh_terms: D000107:Acetylation; D001422:Bacterial Adhesion; D016667:Bacterial Capsules / Q000235:genetics* / Q000276:immunology / Q000378:metabolism*; D016207:Cytokines / Q000378:metabolism; D014644:Genetic Variation; D006801:Humans; D007710:Klebsiella Infections / Q000276:immunology / Q000382:microbiology*; D007711:Klebsiella pneumoniae / Q000145:classification / Q000276:immunology / Q000378:metabolism* / Q000472:pathogenicity; D046290:Liver Abscess, Pyogenic / Q000276:immunology / Q000382:microbiology*; D020935:MAP Kinase Signaling System; D016366:Open Reading Frames
chemical_list: D016207:Cytokines