Why have group A streptococci remained susceptible to penicillin?
In spite of 50 years of extensive use of penicillin, group A streptococci remain exquisitely susceptible to this antibiotic. This observation that continuing susceptibility has occurred despite the development of resistance to other antimicrobial agents prompted a day-long meeting at Rockefeller University (New York) in October 1996. Among the most likely explanations for this remarkable state of continued susceptibility to penicillin are that beta-lactamase may not be expressed or may be toxic to the organism and/or that low-affinity penicillin-binding proteins either are not expressed or render organisms nonviable. Other potential explanations are that circumstances favorable for the development of resistance have not yet occurred and/or that there are inefficient mechanisms for or barriers to genetic transfer. Recommended future actions include (1) additional laboratory investigations of gene transfer, penicillin-binding proteins, virulence factors, and homeologous recombination and
