Bacterial Polysaccharide Vaccines

Capsulated bacteria, Gram-positive or Gram-negative, cause a variety of infections in man. Prominent among them are streptococci of Lancefield’s groups A, B, and C, staphylococci, meningococci, Haemophilus influenzae type b, klebsiellas, Escherichia coli, and Salmonella typhi, to name but some. Since the description of the capsule as an attribute of bacteria more than a century ago, increasing knowledge of its structure and role in interactions of these organisms with their environment has enabled development of vaccines to enhance defenses of their hosts against infection and their likelihood of recovery when it occurs. Since much what has been learned has been derived from studies of the pneumococcus, emphasis in what follows will focus upon Streptococcus pneumoniae, additional references ­pertinent to other specific vaccines are cited where relevant.