title: Cefuroxime non-susceptibility in multidrug-resistant Klebsiella pneumoniae overexpressing ramA and acrA and expressing ompK35 at reduced levels.
abstract: OBJECTIVE
  The aims were to study if efflux and down-regulation of porins contribute to cefuroxime resistance in Klebsiella pneumoniae and to co-resistance to unrelated antibiotics.
  
  
  METHODS
  Ten cefuroxime-non-susceptible but cefotaxime-susceptible blood culture isolates of K. pneumoniae and one multiply antibiotic-resistant (MAR) laboratory strain (selected by chloramphenicol) were examined. Transcription of the genes acrA, ompK35, ramA, marA and soxS was determined with quantitative RT-PCR.
  
  
  RESULTS
  All clinical isolates and the MAR laboratory strain had similar antibiograms with non-susceptibility to cefuroxime, tigecycline, chloramphenicol and nalidixic acid. Phenylalanine arginine beta-naphthylamide (PAbetaN) increased susceptibility to tigecycline, chloramphenicol and nalidixic acid, but not to cefuroxime. Increased acrA transcription and decreased ompK35 transcription was seen in all strains. Increased ramA transcription was seen in all strains except one clinical isolate.
  
  
  CONCLUSIONS
  This multidrug-resistant phenotype of K. pneumoniae is associated with increased acrA and ramA transcription and decreased ompK35 transcription. Since the cefuroxime resistance was not reversed by PAbetaN, it was probably attributable to decreased levels of OmpK35, rather than to efflux.
authors.affiliation: Clinical Microbiology, MTC, Karolinska Institutet, Karolinska University Hospital, Solna, Stockholm, Sweden. owe.kallman@karolinska.se
authors.forename: Owe
authors.initials: O
authors.lastname: Källman
authors.forename: Alma
authors.initials: A
authors.lastname: Motakefi
authors.forename: Bengt
authors.initials: B
authors.lastname: Wretlind
authors.forename: Mats
authors.initials: M
authors.lastname: Kalin
authors.forename: Barbro
authors.initials: B
authors.lastname: Olsson-Liljequist
authors.forename: Christian G
authors.initials: CG
authors.lastname: Giske
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000235:genetics; D001769:Blood / Q000382:microbiology; D002444:Cefuroxime / Q000494:pharmacology*; D024901:Drug Resistance, Multiple, Bacterial; D020869:Gene Expression Profiling; D005798:Genes, Bacterial; D006801:Humans; D007710:Klebsiella Infections / Q000382:microbiology; D007711:Klebsiella pneumoniae / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D018272:Porins / Q000096:biosynthesis* / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D014158:Transcription, Genetic
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; C119261:OmpK35 porin, Klebsiella pneumoniae; D018272:Porins; C095947:RamA protein, Klebsiella; D002444:Cefuroxime