title: Streptococcus pneumoniae in biofilms are unable to cause invasive disease due to altered virulence determinant production.
abstract: It is unclear whether Streptococcus pneumoniae in biofilms are virulent and contribute to development of invasive pneumococcal disease (IPD). Using electron microscopy we confirmed the development of mature pneumococcal biofilms in a continuous-flow-through line model and determined that biofilm formation occurred in discrete stages with mature biofilms composed primarily of dead pneumococci. Challenge of mice with equal colony forming units of biofilm and planktonic pneumococci determined that biofilm bacteria were highly attenuated for invasive disease but not nasopharyngeal colonization. Biofilm pneumococci of numerous serotypes were hyper-adhesive and bound to A549 type II pneumocytes and Detroit 562 pharyngeal epithelial cells at levels 2 to 11-fold greater than planktonic counterparts. Using genomic microarrays we examined the pneumococcal transcriptome and determined that during biofilm formation S. pneumoniae down-regulated genes involved in protein synthesis, energy production, metabolism, capsular polysaccharide (CPS) production, and virulence. We confirmed these changes by measuring CPS by ELISA and immunoblotting for the toxin pneumolysin and the bacterial adhesins phosphorylcholine (ChoP), choline-binding protein A (CbpA), and Pneumococcal serine-rich repeat protein (PsrP). We conclude that biofilm pneumococci were avirulent due to reduced CPS and pneumolysin production along with increased ChoP, which is known to bind C-reactive protein and is opsonizing. Likewise, biofilm pneumococci were hyper-adhesive due to selection for the transparent phase variant, reduced CPS, and enhanced production of PsrP, CbpA, and ChoP. These studies suggest that biofilms do not directly contribute to development of IPD and may instead confer a quiescent mode of growth during colonization.
authors.affiliation: Department of Microbiology and Immunology, The University of Texas Health Science Center at San Antonio, Texas, United States of America.
authors.forename: Carlos J
authors.initials: CJ
authors.lastname: Sanchez
authors.forename: Nikhil
authors.initials: N
authors.lastname: Kumar
authors.forename: Anel
authors.initials: A
authors.lastname: Lizcano
authors.forename: Pooja
authors.initials: P
authors.lastname: Shivshankar
authors.forename: Julie C
authors.initials: JC
authors.lastname: Dunning Hotopp
authors.forename: James H
authors.initials: JH
authors.lastname: Jorgensen
authors.forename: Hervé
authors.initials: H
authors.lastname: Tettelin
authors.forename: Carlos J
authors.initials: CJ
authors.lastname: Orihuela
mesh_terms: D000818:Animals; D000890:Anti-Infective Agents / Q000494:pharmacology; D001422:Bacterial Adhesion / Q000187:drug effects; D016667:Bacterial Capsules / Q000096:biosynthesis / Q000187:drug effects; D001426:Bacterial Proteins / Q000096:biosynthesis; D018441:Biofilms / Q000187:drug effects / Q000254:growth & development*; D002460:Cell Line; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D006801:Humans; D051379:Mice; D008826:Microbial Sensitivity Tests; D010641:Phenotype; D010933:Plankton / Q000187:drug effects / Q000254:growth & development; D011008:Pneumococcal Infections / Q000382:microbiology* / Q000473:pathology*; D015203:Reproducibility of Results; D013296:Streptococcus pneumoniae / Q000187:drug effects / Q000235:genetics / Q000472:pathogenicity* / Q000648:ultrastructure; D013301:Streptolysins / Q000096:biosynthesis; D013997:Time Factors; D014774:Virulence / Q000187:drug effects; D037521:Virulence Factors / Q000096:biosynthesis*
chemical_list: D000890:Anti-Infective Agents; D001426:Bacterial Proteins; C490083:CbpA protein, bacteria; D013301:Streptolysins; D037521:Virulence Factors; C032290:plY protein, Streptococcus pneumoniae