Positive: Medium becomes alkalinized
(blue) because of the growth of the QUALITY CONTROL organism (Figure 13-2, A). Positive: Escherichia coli
Negative: No growth or growth with Negative: Shigella flexneri no indicator change to blue (Figure 13-2, B).
Figure 13-3 Any zone of inhibition is positive (Streptococcus pyogenes); growth up to the disk is negative (Streptococcus algalatiae).
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