title: Antimicrobial resistance among isolates causing invasive pneumococcal disease before and after licensure of heptavalent conjugate pneumococcal vaccine.
abstract: BACKGROUND
  The impact of the pneumococcal conjugate vaccine (PCV-7) on antibiotic resistance among pneumococcal strains causing invasive pneumococcal disease (IPD) has varied in different locales in the United States. We assessed trends in IPD including trends for IPD caused by penicillin non-susceptible strains before and after licensure of PCV-7 and the impact of the 2008 susceptibility breakpoints for penicillin on the epidemiology of resistance.
  
  
  RESULTS
  We performed a retrospective review of IPD cases at Morgan Stanley Children's Hospital of New York-Presbyterian, Columbia University Medical Center. Subjects were < or = 18 years of age with Streptococcus pneumoniae isolated from sterile body sites from January 1995-December 2006. The rate of IPD from 1995-1999 versus 2002-2006 significantly decreased from 4.1 (CI(95) 3.4, 4.8) to 1.7 (CI(95) 1.3, 2.2) per 1,000 admissions. Using the breakpoints in place during the study period, the proportion of penicillin non-susceptible strains increased from 27% to 49% in the pre- vs. post-PCV-7 era, respectively (p = 0.001), although the rate of IPD caused by non-susceptible strains did not change from 1995-1999 (1.1 per 1,000 admissions, CI(95) 0.8, 1.5) when compared with 2002-2006 (0.8 per 1,000 admissions, CI(95) 0.6, 1.2). In the multivariate logistic regression model controlling for the effects of age, strains causing IPD in the post-PCV-7 era were significantly more likely to be penicillin non-susceptible compared with strains in the pre-PCV-7 era (OR 2.46, CI(95) 1.37, 4.40). However, using the 2008 breakpoints for penicillin, only 8% of strains were non-susceptible in the post-PCV-7 era.
  
  
  CONCLUSIONS
  To date, there are few reports that document an increase in the relative proportion of penicillin non-susceptible strains of pneumococci causing IPD following the introduction of PCV-7. Active surveillance of pneumococcal serotypes and antibiotic resistance using the new penicillin breakpoints is imperative to assess potential changes in the epidemiology of IPD.
authors.affiliation: Department of Pediatrics, Columbia University Medical Center, New York, New York, United States of America.
authors.forename: Tom Theodore
authors.initials: TT
authors.lastname: Karnezis
authors.forename: Ann
authors.initials: A
authors.lastname: Smith
authors.forename: Susan
authors.initials: S
authors.lastname: Whittier
authors.forename: Joseph
authors.initials: J
authors.lastname: Haddad
authors.forename: Lisa
authors.initials: L
authors.lastname: Saiman
mesh_terms: D000293:Adolescent; D000890:Anti-Infective Agents / Q000494:pharmacology*; D002648:Child; D002675:Child, Preschool; D024881:Drug Resistance, Bacterial / Q000276:immunology*; D000069443:Heptavalent Pneumococcal Conjugate Vaccine; D006801:Humans; D007223:Infant; D010406:Penicillins / Q000494:pharmacology*; D011008:Pneumococcal Infections / Q000382:microbiology* / Q000517:prevention & control*; D022242:Pneumococcal Vaccines / Q000627:therapeutic use*; D012044:Regression Analysis; D012189:Retrospective Studies; D013296:Streptococcus pneumoniae / Q000378:metabolism*
chemical_list: D000890:Anti-Infective Agents; D000069443:Heptavalent Pneumococcal Conjugate Vaccine; D010406:Penicillins; D022242:Pneumococcal Vaccines