JAC Advance Access originally published online on July 12, 2006
Journal of Antimicrobial Chemotherapy 2006 58(3):678-679; doi:10.1093/jac/dkl261
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In vitro effects of penicillin and telithromycin on the expression of Streptococcus pneumoniae capsule
Departments of Pediatrics and Medicine, Georgetown University and George Washington University, Schools of Medicine 4431 Albemarle St NW, Washington, DC, USA
Received 6 April 2006; returned 2 May 2006; revised 2 May 2006; accepted 1 June 2006
*Corresponding author. Tel: +1-301-295-2698; Fax: +1-253-981-8709; E-mail: ib6{at}georgetown.edu
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.
Keywords: S. pneumoniae , capsular formation , resistance