COMPARISON OF SERUM ANTIBODIES TO PNEUMOLYSIN WITH THOSE TO PNEUMOCOCCAL CAPSULAR POLYSACCHARIDES IN CHILDREN WITH ACUTE OTITIS-MEDIA

Background. Streptococcus pneumoniae is a major bacterial pathogens in acute otitis media, Pneumolysin is a species-specific protein toxin p roduced intracellularly by all clinically relevant pneumococcal strain s, and antibodies to pneumolysin should therefore represent pneumococc al involvement in the disease, regardless of the serotype, Methods, An tibodies to pneumococcal pneumolysin and capsular polysaccharides were measured by enzyme immunoassay in acute and convalescent sera of 121 children with acute otitis media, A pneumococcal otitis episode was de fined by a positive middle ear fluid culture and/or pneumolysin PCR, R esults, Median age of the 10 children who developed a seroconversion r esponse to pneumolysin was 1 year 8 months, and of the 21 children res ponding to polysaccharides it was 2 years 9 months. Eight of the 10 se roconversion responses to pneumolysin were of IgA class alone, whereas 17 of the 21 polysaccharide responses were of IgG class alone or IgG; together with IgM and/or IgA. Of the 41 children with a pneumococcal otitis episode, 13 (39%) showed a seroconversion response, 3 (7%) to p neumolysin and 11 (27%) to capsular polysaccharides. The children with a pneumococcal otitis episode had lower titers of acute phase IgG to the capsular polysaccharide pool of S. pneumoniae (containing types 6B , 14, 19F and 23F), as compared with the titers in children with otiti s caused by other pathogens and pneumococci only in the nasopharynx or not found at all (P = 0.04). Conclusions. Serum antibodies to pneumol ysin can be detected at an earlier age than those to the capsular poly saccharides. However, a seroconversion is rare and therefore of no dia gnostic value. The presence of serum IgG to the pneumococcal capsular polysaccharides seems beneficial in the prevention of pneumococcal oti tis.