title: Biofilm formation by Streptococcus pneumoniae isolates from paediatric patients.
abstract: The clinical significance of pneumococcal biofilm formation is largely unknown. To clarify this, we tested whether the ability of pneumococcal clinical isolates to form biofilm in vitro accounts for the diverse clinical outcomes. Clinical pneumococcal isolates were cultured from the nasopharynx (n=106), middle ear effusion (n=43) and blood (n=55) of 204 children altogether. Biofilm formation, assessed by measuring optical density (OD) values in microtitre plates after crystal violet staining, did not differ between the bacteria from different sources (p=0.18), the mean OD values of the isolates being 0.119 [95% confidence interval (CI) 0.100-0.138] in the nasopharynx samples, 0.094 (95% CI 0.069-0.119) in the acute otitis media cases, 0.109 (95% CI 0.077-0.141) in the secretory otitis media cases, 0.122 (95% CI 0.084-0.160) in those with sepsis and 0.175 (95% CI 0.071-0.280) in those with other invasive infections. Serotypes 33 and 14 were the most efficient in forming biofilms, whereas serotypes 3 and 38 were poor biofilm producers. We conclude that the clinical presentation of pneumococcal disease did not differ in relation to biofilm formation in vitro, even though there was marked variation between the clinical isolates and serotypes.
authors.affiliation: Department of Pediatrics, University of Oulu, and Laboratory of Microbiology, Oulu University Hospital, Oulu, Finland. terhi.tapiainen@oulu.fi
authors.forename: Terhi
authors.initials: T
authors.lastname: Tapiainen
authors.forename: Tiia
authors.initials: T
authors.lastname: Kujala
authors.forename: Tarja
authors.initials: T
authors.lastname: Kaijalainen
authors.forename: Irma
authors.initials: I
authors.lastname: Ikäheimo
authors.forename: Annika
authors.initials: A
authors.lastname: Saukkoriipi
authors.forename: Marjo
authors.initials: M
authors.lastname: Renko
authors.forename: Jarmo
authors.initials: J
authors.lastname: Salo
authors.forename: Maija
authors.initials: M
authors.lastname: Leinonen
authors.forename: Matti
authors.initials: M
authors.lastname: Uhari
mesh_terms: D018441:Biofilms / Q000254:growth & development*; D006801:Humans; D009305:Nasopharynx / Q000382:microbiology; D010033:Otitis Media / Q000382:microbiology*; D010034:Otitis Media with Effusion / Q000382:microbiology; D011008:Pneumococcal Infections / Q000382:microbiology*; D012141:Respiratory Tract Infections / Q000382:microbiology*; D013296:Streptococcus pneumoniae / Q000502:physiology*