In Reply.—The results obtained by Dr Garber demonstrate very well how microorganisms of a single species are not static, but vary in their properties from place to place and from time to time. His bacteriological studies were performed by a technique identical to ours and in conformity with the accepted Kirby-Bauer method.1 Our laboratory consistently found a zero zone of inhibition to erythromycin on disk-susceptibility testing, with daily quality control to ensure disk antimicrobial potency. Because of expressed interest in the question of resistance to antibiotics, we are planning a follow-up study of streptococcal susceptibility to seek corroboration of our findings.
Certainly the susceptibilities of group A β-hemolytic streptococci to antibiotics should be monitored. Because the justification for treatment in the individual patient is the prevention of rheumatic fever, we believe that follow-up cultures of throat material should be made when the patient has been treated with an