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Children are at risk for certain drug-resistant strains of Streptococcus pneumoniae

Streptococcus pneumoniae (pneumococcus) is a leading cause of bacterial meningitis and other serious bacterial infections in children, as well as a major cause of ear infections. Many S. pneumoniae have become resistant to treatment with penicillin or other antibiotics, and some strains of antibiotic-resistant S. pneumoniae are not covered by the current pneumococcal vaccine, according to a study supported by the Agency for Healthcare Research and Quality (HS10247). Universal immunization of all infants with the heptavalent pneumococcal conjugate vaccine (PCV7) against the seven most common invasive serotypes began in 2000.

Jonathan A. Finkelstein, M.D., M.P.H., of Harvard Medical School and the HMO Center for Education and Research on Therapeutics (CERT) in Boston, and his colleagues tested S. pneumoniae isolates from nasopharyngeal specimens of healthy children at 31 Massachusetts primary care practices for resistance to commonly used antibiotics. The researchers serotyped and grouped isolates into PCV7-included serotypes, potentially cross-reactive serotypes (that is, an organism of a serogroup included in the vaccine), or non-PCV7 serotypes. They reviewed children's charts to determine recent antibiotic use, history of PCV7 immunization, and diagnosis.

S. pneumoniae was isolated from the nasopharynx of 26 percent of the 742 children studied. Of the 166 isolates tested, 33 percent were not susceptible to penicillin. Nonsusceptibility to other antibiotics was also common, including ceftriaxone (14 percent), erythromycin (22 percent), and trimethoprim/sulfamethoxazole (31 percent). One-fifth of the S. pneumoniae isolates were not susceptible to three or more antibiotics.

Overall, 36 percent of isolates were of serotypes covered by PCV7, and 30 percent were of PCV7 serogroups and potentially cross-reactive. Forty-five percent of bacteria of covered serotypes were penicillin-resistant, as were 51 percent of potentially cross-reactive strains. Thirty-four percent were unrelated to PCV7 serogroups and therefore would not be covered by the vaccine. Only 8 percent of bacteria in vaccine-unrelated serogroups were resistant to penicillin.

See "Antibiotic-resistant Streptococcus pneumoniae in the heptavalent pneumococcal conjugate vaccine era: Predictors of carriage in a multicommunity sample," by Dr. Finkelstein, Susan S. Huang, M.D., M.P.H., James Daniel, M.P.H., and others, in the October 2003 Pediatrics 112(4), pp. 862-869.

Editor's Note: An article describing a case-control study on bullous myringitis, a particularly painful ear infection in children that in some cases is caused by S. pneumoniae, appears in the same issue of Pediatrics and was supported in part by AHRQ (HS10613). For more information, see McCormick, D.P., Saeed, K.A., Pittman, C., and others, "Bullous myringitis: A case-control study," pp. 982-986.

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