Comparison of virulence between matt and mucoid colonies of Klebsiella pneumoniae coproducing NDM-1 and OXA-232 isolated from a single patient

J Microbiol. 2018 Sep;56(9):665-672. doi: 10.1007/s12275-018-8130-3. Epub 2018 Aug 23.


Nine Klebsiella pneumoniae isolates coproducing NDM-1 and OXA-232 carbapenemases were successively isolated from a single patient. Although they were isolated simultaneously and were isogenic, they presented different colony phenotypes (matt and mucoid). All nine isolates were resistant to most antibiotics except colistin and fosfomycin. In addition, matt-type isolates were resistant to tigecycline. No differences were detected in the cps cluster sequences, except for the insertion of IS5 in the wzb gene of two matt-type isolates. In vitro virulence assays based on production of capsular polysaccharide, biofilm formation, and resistance to human serum indicated that the mucoid-type isolates were significantly more virulent than the matt-type. In addition, mucoid-type isolates showed higher survival rates than the matt-type ones in infection experiments in the fruit fly, suggesting a higher virulence of K. pneumoniae isolates with a mucoid phenotype. To our knowledge, this is the first report of K. pneumoniae colonies with different phenotypes being isolated from the same sample. In addition, we show that virulence varies with colony phenotype. Dissemination of K. pneumoniae isolates expressing both antibiotic resistance and high virulence would constitute a great threat.

Keywords: Drosophila melanogaster; biofilm formation; capsular polysaccharide; carbapenemase; fly infection; serum resistance.

MeSH terms

  • Animals
  • Anti-Bacterial Agents / pharmacology
  • Bacterial Capsules / genetics
  • Bacterial Proteins
  • Biofilms
  • Colistin / pharmacology
  • Drosophila melanogaster / microbiology
  • Drug Resistance, Multiple, Bacterial / genetics*
  • Fosfomycin / pharmacology
  • Gene Expression Regulation, Bacterial
  • Genes, Bacterial / genetics
  • Genotype
  • Humans
  • Klebsiella Infections / microbiology
  • Klebsiella pneumoniae / drug effects
  • Klebsiella pneumoniae / genetics*
  • Klebsiella pneumoniae / isolation & purification
  • Klebsiella pneumoniae / pathogenicity
  • Microbial Sensitivity Tests
  • Minocycline / analogs & derivatives
  • Minocycline / pharmacology
  • Phenotype
  • Serotyping
  • Survival Rate
  • Tigecycline
  • Virulence
  • Virulence Factors / genetics*
  • beta-Lactamases / genetics*


  • Anti-Bacterial Agents
  • Bacterial Proteins
  • Virulence Factors
  • Fosfomycin
  • Tigecycline
  • beta-Lactamases
  • beta-lactamase NDM-1
  • beta-lactamase OXA-232, Klebsiella pneumoniae
  • carbapenemase
  • Minocycline
  • Colistin