title: Surface antigens contribute differently to the pathophysiological features in serotype K1 and K2 Klebsiella pneumoniae strains isolated from liver abscesses.
abstract: BACKGROUND
  The virulence role of surface antigens in a single serotype of Klebsiella pneumoniae strain have been studied, but little is known about whether their contribution will vary with serotype.
  
  
  METHODS
  To investigate the role of K and O antigen in hyper-virulent strains, we constructed O and K antigen deficient mutants from serotype K1 STL43 and K2 TSGH strains from patients with liver abscess, and characterized their virulence in according to the abscess formation and resistance to neutrophil phagocytosis, serum, and bacterial clearance in liver.
  
  
  RESULTS
  Both of K1 and K2-antigen mutants lost their wildtype resistance to neutrophil phagocytosis and hepatic clearance, and failed to cause abscess formation. K2-antigen mutant became serum susceptible while K1-antigen mutant maintained its resistance to serum killing. The amount of glucuronic acid, indicating the amount of capsular polysaccharide (CPS, K antigen), was inversed proportional to the rate of phagocytosis. O-antigen mutant of serotype K1 strains had significantly more amount of CPS, and more resistant to neutrophil phagocytosis than its wildtype counterpart. O-antigen mutants of serotype K1 and K2 strains lost their wildtype serum resistance, and kept resistant to neutrophil phagocytosis. While both mutants lacked the same O1 antigen, O-antigen mutant of serotype K1 became susceptible to liver clearance and cause mild abscess formation, but its serotype K2 counterpart maintained these wildtype virulence.
  
  
  CONCLUSIONS
  We conclude that the contribution of surface antigens to virulence of K. pneumoniae strains varies with serotypes.
authors.affiliation: Department of Internal Medicine, Division of Infectious Diseases and Tropical Medicine, Tri-Service General Hospital, National Defense Medical Center, No. 325, Sec. 2, Cheng-Kung Road, Neihu, 114 Taipei City Taiwan ; Infection Control Office, Tri-Service General Hospital, National Defense Medical Center, No. 325, Sec. 2, Cheng-Kung Road, Neihu, 114 Taipei City Taiwan.
authors.forename: Kuo-Ming
authors.initials: KM
authors.lastname: Yeh
authors.affiliation: Department of Internal Medicine, Division of Infectious Diseases and Tropical Medicine, Tri-Service General Hospital, National Defense Medical Center, No. 325, Sec. 2, Cheng-Kung Road, Neihu, 114 Taipei City Taiwan.
authors.forename: Sheng-Kung
authors.initials: SK
authors.lastname: Chiu
authors.affiliation: School of Respiratory Therapy, College of Medicine, Taipei Medical University, Taipei, Taiwan ; Department of Internal Medicine, Division of Pulmonary Medicine, Shuang Ho Hospital, Taipei Medical University, New Taipei City, Taiwan.
authors.forename: Chii-Lan
authors.initials: CL
authors.lastname: Lin
authors.affiliation: Institute of Infectious Diseases and Vaccine Research, National Health Research Institutes, 35 Keyan Road, Zhunan, 35053 Miaoli, Taiwan.
authors.forename: Li-Yueh
authors.initials: LY
authors.lastname: Huang
authors.affiliation: Institute of Infectious Diseases and Vaccine Research, National Health Research Institutes, 35 Keyan Road, Zhunan, 35053 Miaoli, Taiwan.
authors.forename: Yu-Kuo
authors.initials: YK
authors.lastname: Tsai
authors.affiliation: Institute of Infectious Diseases and Vaccine Research, National Health Research Institutes, 35 Keyan Road, Zhunan, 35053 Miaoli, Taiwan.
authors.forename: Jen-Chang
authors.initials: JC
authors.lastname: Chang
authors.affiliation: Department of Internal Medicine, Division of Infectious Diseases and Tropical Medicine, Tri-Service General Hospital, National Defense Medical Center, No. 325, Sec. 2, Cheng-Kung Road, Neihu, 114 Taipei City Taiwan.
authors.forename: Jung-Chung
authors.initials: JC
authors.lastname: Lin
authors.affiliation: Department of Internal Medicine, Division of Infectious Diseases and Tropical Medicine, Tri-Service General Hospital, National Defense Medical Center, No. 325, Sec. 2, Cheng-Kung Road, Neihu, 114 Taipei City Taiwan.
authors.forename: Feng-Yee
authors.initials: FY
authors.lastname: Chang
authors.affiliation: Department of Internal Medicine, Division of Infectious Diseases and Tropical Medicine, Tri-Service General Hospital, National Defense Medical Center, No. 325, Sec. 2, Cheng-Kung Road, Neihu, 114 Taipei City Taiwan ; Institute of Infectious Diseases and Vaccine Research, National Health Research Institutes, 35 Keyan Road, Zhunan, 35053 Miaoli, Taiwan ; Graduate Institute of Basic Medical Science, China Medical University, Taichung, Taiwan.
authors.forename: Leung-Kei
authors.initials: LK
authors.lastname: Siu