Phagocytosis tests with M1 and M3 strains.

<p>(<b>A</b>) Suspensions of the bacterial strains indicated were analyzed for ability to bind human FH. After incubation of a bacterial suspension with pure FH (50 µg/ml), the bacteria were washed twice and bound protein was eluted and analyzed by western blot, employing anti-FH for detection. The analysis included wild type M5, M1 and M3 strains and their M-negative mutants (ΔM5, ΔM1 and ΔM3, respectively). Pure FH was included as a control in the blot (right). (<b>B</b>) Phagocytosis assay in whole human blood with M1 and M3 strains, and M-negative mutants, as indicated. MF, multiplication factor.