Sensitivity to serum complement-mediated bactericidal activity for M. catarrhalis strain 2951 and 2591 galE mutant after 30 min. ▧, results obtained with M. catarrhalis 2951 and heat-inactivated PNHS; ▨, results obtained with M. catarrhalis 2951 galE and inactivated PNHS; □, results obtained with M. catarrhalis 2951 and PNHS; , results obtained with M. catarrhalis 2951 galE and PNHS. P values, comparisons between survival of strain 2951 and that of 2951 galE in PNHS. Each result is the mean from four separate experiments ± 1 standard deviation.