New Selective Media for the Isolation ofStreptococcus hemolyticus

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Abstract
A new enrichment broth (E.U.B.) and a modified agar medium (M.H.A) were devised for the purpose of obtaining β-streptococci selectively in increasing numbers from throat swabs. The new broth replaces animal blood with activated charcoal, uses a high concentration of NaCl (3%), saponin, DL-camphor, and sodium azide as inhibitory agents against contaminants, and includes urease as a stimulating agent for β-streptococci. Urea is added to the modified agar medium to promote the growth of β-streptococci, and crystal violet assists by inhibiting the proliferation of staphylococci. The incidences of positive cultures of β-streptococci from 1,225 throat swabs from 112 patients with scarlet fever were 47.2% (579) with the new media and 23.6% (290 cultures) by the routine anaerobic blood agar method. Furthermore, β-streptococci from 11 throat swabs collected from patients after antibiotic therapy had been instituted could be isolated only by the new culture method.

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