Table 2. SpeB activity phenotype correlates with GAS disease.

	Columbia agar with skim milk a				C-broth agar with casein (extrapolated values) c
Disease group	No. of SpeB- producers	No. of SpeB- non-producers	% SpeB- non-producers	p value, pharyngitis versus b:	No. of SpeB- producers	No. of SpeB-non-producers	% SpeB- non-producers	p value, pharyngitis versus b:
Pharyngitis	116	30	20.5	n/a	106	32	23.7	n/a
Impetigo	69	4	5.5	0.0029	69	4	5.5	0.0009
Invasive	50	10	16.7	N.S.	44	12	21.4	N.S.
ARF	24	17	41.5	0.0085	20	20	50.0	0.0016

^a One ARF and one impetigo isolate had intermediate ("weak") zones of clearance on Columbia-SM agar (S1 Table), and are excluded from the calculations.

^b Fisher's exact test, 2-tailed; N.S., non-significant.

^c Data extrapolations for the complete set of GAS organisms are made for impetigo and pharyngitis isolates (italics). Organisms with intermediate ("weak") zones of clearance on CBrothMg-C agar (S1 Table) are excluded from the calculations.