title: Increasing prevalence of multidrug-resistant Streptococcus pneumoniae in the United States.
abstract: BACKGROUND
  The emergence of drug-resistant strains of bacteria has complicated treatment decisions and may lead to treatment failures.
  
  
  METHODS
  We examined data on invasive pneumococcal disease in patients identified from 1995 to 1998 in the Active Bacterial Core Surveillance program of the Centers for Disease Control and Prevention. Pneumococci that had a high level of resistance or had intermediate resistance according to the definitions of the National Committee for Clinical Laboratory Standards were defined as "resistant" for this analysis.
  
  
  RESULTS
  During 1998, 4013 cases of invasive Streptococcus pneumoniae disease were reported (23 cases per 100,000 population); isolates were available for 3475 (87 percent). Overall, 24 percent of isolates from 1998 were resistant to penicillin. The proportion of isolates that were resistant to penicillin was highest in Georgia (33 percent) and Tennessee (35 percent), in children under five years of age (32 percent, vs. 21 percent for persons five or more years of age), and in whites (26 percent, vs. 22 percent for blacks). Penicillin-resistant isolates were more likely than susceptible isolates to have a high level of resistance to other antimicrobial agents. Serotypes included in the 7-valent conjugate and 23-valent pneumococcal polysaccharide vaccines accounted for 78 percent and 88 percent of penicillin-resistant strains, respectively. Between 1995 and 1998 (during which period 12,045 isolates were collected), the proportion of isolates that were resistant to three or more classes of drugs increased from 9 percent to 14 percent; there also were increases in the proportions of isolates that were resistant to penicillin (from 21 percent to 25 percent), cefotaxime (from 10 percent to 15 percent), meropenem (from 10 percent to 16 percent), erythromycin (from 11 percent to 16 percent), and trimethoprim-sulfamethoxazole (from 25 percent to 29 percent). The increases in the frequency of resistance to other antimicrobial agents occurred exclusively among penicillin-resistant isolates.
  
  
  CONCLUSIONS
  Multidrug-resistant pneumococci are common and are increasing. Because a limited number of serotypes account for most infections with drug-resistant strains, the new conjugate vaccines offer protection against most drug-resistant strains of S. pneumoniae.
authors.affiliation: Division of Bacterial and Mycotic Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, USA.
authors.forename: C G
authors.initials: CG
authors.lastname: Whitney
authors.forename: M M
authors.initials: MM
authors.lastname: Farley
authors.forename: J
authors.initials: J
authors.lastname: Hadler
authors.forename: L H
authors.initials: LH
authors.lastname: Harrison
authors.forename: C
authors.initials: C
authors.lastname: Lexau
authors.forename: A
authors.initials: A
authors.lastname: Reingold
authors.forename: L
authors.initials: L
authors.lastname: Lefkowitz
authors.forename: P R
authors.initials: PR
authors.lastname: Cieslak
authors.forename: M
authors.initials: M
authors.lastname: Cetron
authors.forename: E R
authors.initials: ER
authors.lastname: Zell
authors.forename: J H
authors.initials: JH
authors.lastname: Jorgensen
authors.forename: A
authors.initials: A
authors.lastname: Schuchat
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D018432:Drug Resistance, Multiple; D006801:Humans; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D010403:Penicillin Resistance; D011008:Pneumococcal Infections / Q000453:epidemiology / Q000382:microbiology*; D011159:Population Surveillance; D015995:Prevalence; D012703:Serotyping; D013296:Streptococcus pneumoniae / Q000145:classification / Q000187:drug effects / Q000302:isolation & purification; D014481:United States / Q000453:epidemiology