Pneumococcal serotypes from acute otitis media in rural Kentucky

Objective. Acute otitis media (AOM) accounts for most infections caused by Streptococcus pneumoniae, but few data are available regarding the incidence of pneumococcal serotypes recovered from children with AOM in the United States. Methods. Between January 1992 and March 1998, 777 middle ear pathogens from AOM were obtained from 701 patients by tympanocentesis (84.6%) or by culture of otorrhea (15.4%) from spontaneous perforation or draining tubes. The ambulatory patient population was mostly white and cared for by a sole private pediatric practice in rural Kentucky. Results. Penicillin-nonsusceptible (penicillin MIC greater than or equal to 0.1 mug/ml) Streptococcus pneumoniae (PNSP) isolates accounted for 18% [6% resistant PNSP (rPNSP) and 12% intermediate resistant PNSP], and penicillin-susceptible S. pneumoniae strains accounted for 35% of the pathogens recovered from children with culture-proved AOM. Comparing the frequency of isolates between 1992 and 1993 with those between 1994 and 1998, overall rates of PNSP strains remained remarkably stable (32.2% us. 37.3%), but intermediate resistant PNSP strains doubled from 14% to 27% (P < 0.01), whereas rPNSP strains fell by one-third. Serotypes 19F (34%), 23F (30%), 6B (26%) and 14 (8%) accounted for nearly all rPNSP isolates. Two cross-reactive serotypes (6A and 19A) not included in the available pneumococcal conjugate vaccine comprised 8.4 and 15% of all serotypes and PNSP serotypes, respectively. Nearly all PNSP strains recovered in children <= 24 months are included in the vaccine serogroups. Conclusion. Depending on rates of efficacy and serotype cross-protection, the current pneumococcal conjugate vaccine could potentially protect against most PNSP strains in all ages, particularly in those <= 24 months.