The Journal of Medical Microbiology, Vol 16, Issue 1 69-74, Copyright © 1983 by Society for General Microbiology
The relative importance of the classical and alternative complement pathways in serum bactericidal activity against Escherichia coli
A. P. Roberts and R. Phillips
The relative importance of the classical and alternative complement
pathways in serum bactericidal activity against Escherichia coli strains of
the common urinary O-serogroups has been assessed with strains that differ
widely in their sensitivity to normal human serum. With most promptly
serum-sensitive strains, rapid killing occurred, mediated by the classical
pathway and, when this pathway was eliminated, delayed killing by
alternative-pathway activity occurred. However, one strain of serogroup O1
was affected by the classical pathway only and a strain of serogroup O9 was
killed rapidly by the alternative pathway. Strains with delayed sensitivity
to normal human serum were largely, and in some cases exclusively, affected
by the classical pathway. When added to heat-inactivated serum, some
strains showed no significant growth whereas the viable numbers of other
test strains increased more than 50-fold in 3 h. Whether this variation is
due to differences in nutritional requirements or sensitivity to some
non-complement-dependent bacteriostatic mechanism remains to be determined.
