title: In vivo selection of OmpK35-deficient mutant after cefuroxime therapy for primary liver abscess caused by Klebsiella pneumoniae.
abstract: OBJECTIVE
  The aim of the study was to characterize the genetic basis of beta-lactam resistance developed in clinical isolates of Klebsiella pneumoniae after exposure to cefuroxime.
  
  
  METHODS
  Clinical features of two episodes of liver abscess caused by K. pneumoniae in a diabetic patient were reported. Four isolates (KP(1)/KP(2) and KP(3)/KP(4)) of K. pneumoniae were recovered from cultures of blood/pus in the first and second episodes, respectively. Laboratory investigation of the K. pneumoniae isolates included genotyping by PFGE, resistance gene analysis by PCR amplification and DNA sequencing, and outer membrane protein analysis by SDS-PAGE.
  
  
  RESULTS
  KP(3) and KP(4) were recovered after a 21 day cefuroxime therapy and demonstrated identical genotypes to that of KP(1) and KP(2). However, compared with KP(1) and KP(2), emerging resistance to piperacillin, cefalotin, cefuroxime and cefoxitin was observed. The other antibiotics tested, except ampicillin, retained the same effectiveness against the four isolates, although increases (4- to 8-fold) in the MICs of cefotaxime, ceftriaxone, ceftazidime, cefepime, flomoxef and aztreonam were observed in KP(3) and KP(4). None of the isolates produced extended-spectrum beta-lactamases or plasmid-mediated AmpC beta-lactamases. Deficiency in the expression of an outer membrane protein (OmpK35) was observed in the cefuroxime-resistant isolates, KP(3) and KP(4).
  
  
  CONCLUSIONS
  The increased resistance to cephalosporins in these clinical isolates of K. pneumoniae after exposure to cefuroxime might be related to the loss of OmpK35.
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, Kaohsiung Medical Center, Chang Gung Memorial Hospital, Chang Gung University College of Medicine 123 Ta-Pei Road, Niao-Sung, Kaohsiung 833, Taiwan.
authors.forename: Chen-Hsiang
authors.initials: CH
authors.lastname: Lee
authors.forename: Ju-Hsin
authors.initials: JH
authors.lastname: Chia
authors.forename: Chishih
authors.initials: C
authors.lastname: Chu
authors.forename: Tsu-Lan
authors.initials: TL
authors.lastname: Wu
authors.forename: Jien-Wei
authors.initials: JW
authors.lastname: Liu
authors.forename: Lin-Hui
authors.initials: LH
authors.lastname: Su
mesh_terms: D000328:Adult; D000900:Anti-Bacterial Agents / Q000494:pharmacology / Q000627:therapeutic use*; D001426:Bacterial Proteins / Q000235:genetics*; D002444:Cefuroxime / Q000494:pharmacology / Q000627:therapeutic use*; D018550:Cephalosporin Resistance; D006801:Humans; D007710:Klebsiella Infections / Q000188:drug therapy / Q000382:microbiology; D007711:Klebsiella pneumoniae / Q000145:classification / Q000187:drug effects* / Q000235:genetics; D008100:Liver Abscess / Q000188:drug therapy* / Q000382:microbiology; D008297:Male; D008826:Microbial Sensitivity Tests; D009154:Mutation; D018272:Porins / Q000172:deficiency / Q000235:genetics*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; C119261:OmpK35 porin, Klebsiella pneumoniae; D018272:Porins; D002444:Cefuroxime