title: In vitro effects of penicillin and telithromycin on the expression of Streptococcus pneumoniae capsule.
abstract: OBJECTIVE
  To evaluate the effects of subinhibitory concentrations of penicillin and telithromycin on capsular formation by Streptococcus pneumoniae.
  
  
  METHODS
  A total of 60 isolates of S. pneumoniae, 20 susceptible, 20 intermediately resistant and 20 resistant to penicillin, were studied. All isolates were susceptible to telithromycin.
  
  
  RESULTS
  All isolates were capsulate when grown without antibiotics. Encapsulation was lower after incubation with telithromycin as compared with penicillin in isolates susceptible to penicillin (20% versus 75%), in those intermediately resistant to penicillin (25% versus 95%) and in isolates fully resistant to penicillin (15% versus 100%) (P < 0.01).
  
  
  CONCLUSIONS
  Telithromycin appears to be superior to penicillin in reducing the expression of the capsule by S. pneumoniae.
authors.affiliation: Department of Pediatrics and Medicine, Georgetown University and George Washington University, Schools of Medicine, Washington, DC, USA. ib6@georgetown.edu
authors.forename: Itzhak
authors.initials: I
authors.lastname: Brook
authors.forename: Jeffrey N
authors.initials: JN
authors.lastname: Hausfeld
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D016667:Bacterial Capsules / Q000096:biosynthesis* / Q000648:ultrastructure; D006801:Humans; D048628:Ketolides / Q000494:pharmacology*; D015523:Maxillary Sinusitis / Q000382:microbiology; D008826:Microbial Sensitivity Tests; D010403:Penicillin Resistance / Q000235:genetics*; D013290:Streptococcal Infections / Q000382:microbiology; D013296:Streptococcus pneumoniae / Q000187:drug effects / Q000302:isolation & purification / Q000648:ultrastructure
chemical_list: D000900:Anti-Bacterial Agents; D048628:Ketolides; C106791:telithromycin