title: Geographic and temporal trends in antimicrobial nonsusceptibility in Streptococcus pneumoniae in the post-vaccine era in the United States.
abstract: BACKGROUND
  We examined whether observed increases in antibiotic nonsusceptible nonvaccine serotypes after introduction of pneumococcal conjugate vaccine in the United States in 2000 were driven primarily by vaccine or antibiotic use.
  
  
  METHODS
  Using active surveillance data, we evaluated geographic and temporal differences in serotype distribution and within-serotype differences during 2000-2009. We compared nonsusceptibility to penicillin and erythromycin by geography after standardizing differences across time, place, and serotype by regressing standardized versus crude proportions. A regression slope (RS) approaching zero indicates greater importance of the standardizing factor.
  
  
  RESULTS
  Through 2000-2006, geographic differences in nonsusceptibility were better explained by within-serotype prevalence of nonsusceptibility (RS 0.32, 95% confidence interval [CI], .08-.55 for penicillin) than by geographic differences in serotype distribution (RS 0.71, 95% CI, .44-.97). From 2007-2009, serotype distribution differences became more important for penicillin (within-serotype RS 0.52, 95% CI, .11-.93; serotype distribution RS 0.57, 95% CI, .14-1.0).
  
  
  CONCLUSIONS
  Differential nonsusceptibility, within individual serotypes, accounts for most geographic variation in nonsusceptibility, suggesting selective pressure from antibiotic use, rather than differences in serotype distribution, mainly determines nonsusceptibility patterns. Recent trends suggest geographic differences in serotype distribution may be affecting the prevalence of nonsusceptibility, possibly due to decreases in the number of nonsusceptible serotypes.
authors.affiliation: Respiratory Diseases Branch, Division of Bacterial Diseases, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: Ruth
authors.initials: R
authors.lastname: Link-Gelles
authors.forename: Ann
authors.initials: A
authors.lastname: Thomas
authors.forename: Ruth
authors.initials: R
authors.lastname: Lynfield
authors.forename: Sue
authors.initials: S
authors.lastname: Petit
authors.forename: William
authors.initials: W
authors.lastname: Schaffner
authors.forename: Lee
authors.initials: L
authors.lastname: Harrison
authors.forename: Monica M
authors.initials: MM
authors.lastname: Farley
authors.forename: Deborah
authors.initials: D
authors.lastname: Aragon
authors.forename: Megin
authors.initials: M
authors.lastname: Nicols
authors.forename: Pam Daily
authors.initials: PD
authors.lastname: Kirley
authors.forename: Shelley
authors.initials: S
authors.lastname: Zansky
authors.forename: James
authors.initials: J
authors.lastname: Jorgensen
authors.forename: Billie Anne
authors.initials: BA
authors.lastname: Juni
authors.forename: Delois
authors.initials: D
authors.lastname: Jackson
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Moore
authors.forename: Marc
authors.initials: M
authors.lastname: Lipsitch
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial; D004917:Erythromycin / Q000494:pharmacology; D006801:Humans; D008826:Microbial Sensitivity Tests; D010406:Penicillins / Q000494:pharmacology; D011008:Pneumococcal Infections / Q000453:epidemiology / Q000382:microbiology*; D022242:Pneumococcal Vaccines / Q000008:administration & dosage*; D062486:Public Health Surveillance; D012044:Regression Analysis; D018709:Statistics, Nonparametric; D013296:Streptococcus pneumoniae / Q000187:drug effects* / Q000302:isolation & purification; D014481:United States / Q000453:epidemiology
chemical_list: D000900:Anti-Bacterial Agents; D010406:Penicillins; D022242:Pneumococcal Vaccines; D004917:Erythromycin
keywords: Streptococcus pneumoniae; antimicrobial resistance; erythromycin; invasive pneumococcal disease; penicillin; pneumococcus