title: Phenotypic heterogeneity enables uropathogenic Escherichia coli to evade killing by antibiotics and serum complement.
abstract: Uropathogenic strains of Escherichia coli (UPEC) are the major cause of bacteremic urinary tract infections. Survival in the bloodstream is associated with different mechanisms that help to resist serum complement-mediated killing. While the phenotypic heterogeneity of bacteria has been shown to influence antibiotic tolerance, the possibility that it makes cells refractory to killing by the immune system has not been experimentally tested. In the present study we sought to determine whether the heterogeneity of bacterial cultures is relevant to bacterial targeting by the serum complement system. We monitored cell divisions in the UPEC strain CFT073 with fluorescent reporter protein. Stationary-phase cells were incubated in active or heat-inactivated human serum in the presence or absence of different antibiotics (ampicillin, norfloxacin, and amikacin), and cell division and complement protein C3 binding were measured by flow cytometry and immunofluorescence microscopy. Heterogeneity in the doubling times of CFT073 cells in serum enabled three phenotypically different subpopulations to be distinguished, all of them being recognized by the C3 component of the complement system. The population of rapidly growing cells resists serum complement-mediated lysis. The dominant subpopulation of cells with intermediate growth rate is susceptible to serum. The third population, which does not resume growth upon dilution from stationary phase, is simultaneously protected from serum complement and antibiotics.
authors.affiliation: Institute of Technology, University of Tartu, Tartu, Estonia.
authors.forename: Marta
authors.initials: M
authors.lastname: Putrinš
authors.affiliation: Institute of Technology, University of Tartu, Tartu, Estonia.
authors.forename: Karin
authors.initials: K
authors.lastname: Kogermann
authors.affiliation: Institute of Technology, University of Tartu, Tartu, Estonia.
authors.forename: Eliisa
authors.initials: E
authors.lastname: Lukk
authors.affiliation: Institute of Technology, University of Tartu, Tartu, Estonia.
authors.forename: Markus
authors.initials: M
authors.lastname: Lippus
authors.affiliation: Institute of Technology, University of Tartu, Tartu, Estonia.
authors.forename: Vallo
authors.initials: V
authors.lastname: Varik
authors.affiliation: Institute of Technology, University of Tartu, Tartu, Estonia tanel.tenson@ut.ee.
authors.forename: Tanel
authors.initials: T
authors.lastname: Tenson
mesh_terms: D000583:Amikacin / Q000494:pharmacology; D000667:Ampicillin / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D003176:Complement C3 / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial; D018740:Genetic Heterogeneity; D005838:Genotype; D006801:Humans; D008826:Microbial Sensitivity Tests; D008856:Microscopy, Fluorescence; D009643:Norfloxacin / Q000494:pharmacology; D010641:Phenotype; D056689:Uropathogenic Escherichia coli / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development / Q000648:ultrastructure
chemical_list: D000900:Anti-Bacterial Agents; D003176:Complement C3; D000667:Ampicillin; D000583:Amikacin; D009643:Norfloxacin