Because of reported differences in the production of streptococcal pyrogenic exotoxins by group A strains associated with severe streptococcal infections, the stability of exotoxin production by specific strains was examined by passing group A streptococci on blood agar culture plates daily for 20 days. No changes were detected in either exotoxin genes or in exotoxin production during this time, suggesting that these reported differences are due to other explanations such as differences in the strains collected from various geographic areas or to laboratory methodologic differences.
Bibliographical noteFunding Information:
Received 7 May 1991; revised I7 July 1991. Grant support: Emma B. Howe Foundation and National Institutes of Health (HL-36611). Reprints or correspondence: Dr. Edward L. Kaplan, Department ofPediatrics, Box 296 UMHC, University ofMinnesota Medical School, 420 Delaware St. S.E., Minneapolis, MN 55455.
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