title: Studies of the continuing susceptibility of group A streptococcal strains to penicillin during eight decades.
abstract: BACKGROUND
  In view of the widespread use of penicillin for >50 years for the treatment of group A streptococcal infections, we examined the question of whether there has been a change in susceptibility to penicillin in group A streptococcal strains collected during a span of 80 years (1917 to 1997).
  
  
  METHODS
  One hundred thirty-three group A streptococcal strains collected during 80 years were tested for changes in penicillin susceptibility. Three tests were used: (1) the microtiter broth minimal inhibitory concentration (MIC); (2) the minimal bactericidal concentration (MBC); and (3) the penicillin E strip MIC.
  
  
  RESULTS
  The results indicate there has been no change in the susceptibility to penicillin in these group A streptococci during the past 80 years. The microtiter broth MIC90 for the oldest strains (0.032 microg/ml) was not significantly different from those collected most recently (0.032 microg/ml); there is no statistical difference between the raw MIC data for the four collection periods (P=0.468, analysis of variance on ranks).
  
  
  CONCLUSIONS
  There has been no change in the susceptibility of group A streptococci during this time in spite of well-documented cases of penicillin resistance in other Gram-positive organisms and despite recognized resistance of group A streptococci to other antibiotics.
authors.affiliation: The Rockefeller University, New York, NY 10021, USA.
authors.forename: M H
authors.initials: MH
authors.lastname: Macris
authors.forename: N
authors.initials: N
authors.lastname: Hartman
authors.forename: B
authors.initials: B
authors.lastname: Murray
authors.forename: R F
authors.initials: RF
authors.lastname: Klein
authors.forename: R B
authors.initials: RB
authors.lastname: Roberts
authors.forename: E L
authors.initials: EL
authors.lastname: Kaplan
authors.forename: D
authors.initials: D
authors.lastname: Horn
authors.forename: J B
authors.initials: JB
authors.lastname: Zabriskie
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D006801:Humans; D007769:Lactams; D008826:Microbial Sensitivity Tests; D010403:Penicillin Resistance; D010406:Penicillins / Q000494:pharmacology*; D013297:Streptococcus pyogenes / Q000187:drug effects*; D013997:Time Factors
chemical_list: D000900:Anti-Bacterial Agents; D007769:Lactams; D010406:Penicillins