title: Heteroresistance to colistin in Klebsiella pneumoniae is triggered by small colony variants sub-populations within biofilms.
abstract: The emergence of Klebsiella pneumoniae multidrug-resistant strains paves the way to the re-introduction of colistin as a salvage therapy. However, recent planktonic studies have reported several cases of heteroresistance to this antimicrobial agent. The aim of this present work was to gain better understanding about the response of K. pneumoniae biofilms to colistin antibiotherapy and inspect the occurrence of heteroresistance in biofilm-derived cells. Biofilm formation and its susceptibility to colistin were evaluated through the determination of biofilm-cells viability. The profiling of planktonic and biofilm cell populations was conducted to assess the occurrence of heteroresistance. Colony morphology was further characterized in order to inspect the potential role of colistin in K. pneumoniae phenotypic differentiation. Results show that K. pneumoniae was susceptible to colistin in its planktonic form, but biofilms presented enhanced resistance. Population analysis profiles pointed out that K. pneumoniae manifest heteroresistance to colistin only when grown in biofilm arrangements, and it was possible to identify a resistant sub-population presenting a small colony morphology (diameter around 5 mm). To the best of our knowledge, this is the first report linking heteroresistance to biofilm formation and a morphological distinctive sub-population. Moreover, this is the first evidence that biofilm formation can trigger the emergence of heteroresistance in an apparently susceptible strain.
authors.affiliation: CEB-Centre of Biological Engineering, LIBRO-Laboratory of Research in Biofilms Rosário Oliveira, University of Minho, Braga, Portugal.
authors.forename: Ana
authors.initials: A
authors.lastname: Silva
authors.affiliation: CEB-Centre of Biological Engineering, LIBRO-Laboratory of Research in Biofilms Rosário Oliveira, University of Minho, Braga, Portugal.
authors.forename: Ana Margarida
authors.initials: AM
authors.lastname: Sousa
authors.affiliation: CEB-Centre of Biological Engineering, LIBRO-Laboratory of Research in Biofilms Rosário Oliveira, University of Minho, Braga, Portugal.
authors.forename: Diana
authors.initials: D
authors.lastname: Alves
authors.affiliation: ESEI-Escuela Superior de Ingeniería Informática, Universidad de Vigo, Ourense, Spain CEB-Centre of Biological Engineering, University of Minho, Braga, Portugal.
authors.forename: Anália
authors.initials: A
authors.lastname: Lourenço
authors.affiliation: CEB-Centre of Biological Engineering, LIBRO-Laboratory of Research in Biofilms Rosário Oliveira, University of Minho, Braga, Portugal mopereira@deb.uminho.pt.
authors.forename: Maria Olívia
authors.initials: MO
authors.lastname: Pereira
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects*; D003091:Colistin / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial; D007711:Klebsiella pneumoniae / Q000187:drug effects* / Q000502:physiology*; D008826:Microbial Sensitivity Tests; D010641:Phenotype
chemical_list: D000900:Anti-Bacterial Agents; D003091:Colistin
keywords: Klebsiella pneumoniae; biofilm; colistin; heteroresistance; small colony variants