title: Penicillin susceptibility of pneumococcal isolates causing acute otitis media in children: seasonal variation.
abstract: BACKGROUND
  During the past decade, the prevalence of nonsusceptible Streptococcus pneumoniae strains that cause acute otitis media (AOM) has increased to approximately 30%, and the proportion of fully resistant strains has also increased. The purpose of this study was to determine whether seasonal variation in resistance exists among pneumococcal isolates from children with AOM.
  
  
  METHODS
  Between 1991 and 2003, children 2 months-8 years of age diagnosed with AOM according to stringent criteria underwent tympanocentesis in various clinical trials.
  
  
  RESULTS
  Cultures from 567 of 794 tympanocenteses (71.4%) performed between 1991 and 2003 yielded AOM pathogens. During 1991-1995, only 1 of 43 S. pneumoniae isolates recovered (2%) was nonsusceptible to penicillin. The present analysis focuses on the 691 cultures obtained during 1996-2003; of these, 491 (71.1%) yielded AOM pathogens, of which 165 (33.6%) were S. pneumoniae. Of the pneumococcal isolates, 52 (31.5%) were nonsusceptible to penicillin. The proportion of nonsusceptible strains of S. pneumoniae increased over time: 0 of 3 (0%) in 1996; 2 of 11 (18%) in 1997; 14 of 40 (35%) in 1998; 3 of 34 (9%) in 1999; 11 of 25 (44%) in 2000; 11 of 22 (50%) in 2001; 4 of 18 (22%) in 2002; and 7 of 12 (58%) in 2003 (Cochran Armitage trend test, P = 0.03). AOM caused by nonsusceptible S. pneumoniae was more likely to occur as the winter progressed (P = 0.03); a similar trend was noted for the proportion of nonsusceptible strains that were fully resistant.
  
  
  CONCLUSIONS
  In children with AOM, an increase in the proportion of episodes caused by nonsusceptible S. pneumoniae as the winter months progress may serve as a potential factor in guiding antimicrobial therapy for such children.
authors.affiliation: Department of Pediatrics, University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh, Pittsburgh, PA 15213, USA. hoberman@chp.edu
authors.forename: Alejandro
authors.initials: A
authors.lastname: Hoberman
authors.forename: Jack L
authors.initials: JL
authors.lastname: Paradise
authors.forename: David P
authors.initials: DP
authors.lastname: Greenberg
authors.forename: Ellen R
authors.initials: ER
authors.lastname: Wald
authors.forename: Diana H
authors.initials: DH
authors.lastname: Kearney
authors.forename: D Kathleen
authors.initials: DK
authors.lastname: Colborn
mesh_terms: D002648:Child; D002675:Child, Preschool; D006801:Humans; D007223:Infant; D010033:Otitis Media / Q000382:microbiology*; D010403:Penicillin Resistance; D010414:Pennsylvania / Q000453:epidemiology; D011008:Pneumococcal Infections / Q000453:epidemiology / Q000382:microbiology*; D012621:Seasons; D013296:Streptococcus pneumoniae / Q000187:drug effects*