FIG. 1.

Comparison of biofilm formation by several S. pneumoniae serotypes on polystyrene plates. Laboratory and clinical isolates of the indicated serotypes were inoculated in 96-well microtiter plates and allowed to statically form a biofilm. Bacteria were inoculated in THY (A) or THY with 0.3% glucose (B) and incubated for 14 h, at which time supernatants containing planktonic cells were discarded and attached biofilms were washed three times with PBS, stained with 0.05% CV for 30 min, dissolved in 95% ethanol, and quantified by measuring the absorbance at 570 nm (OD570). c−, acapsular. Strains were inoculated in quadruplicate. Results are representative of three experiments. Error bars show standard deviations.