TABLE 2.

Detection of Stx in STEC strain supernatants and enriched stool cultures by conventional assays and by immuno-PCR

Sample (no. of samples)	stx genotype	Conventional assaysa	Immuno-PCR detection of Stxb
			Undiluted	1:10	1:100
STEC low producers (6)	stx2dc	−	+	+	−
	stx2ed	−	+	+	−
STEC controls (4)	stx2de	+	+	+	+
	stx2ef	+	+	+	+
	stx1, stx2g	+	+	+	+
Nonproducers (20)	—h	−	−	−	−
Stool samples (3)	stx2	−	+	ND	ND
Stool samples (10)	—	−	−	ND	ND

^aConventional assays include the Vero cell cytotoxicity assay, the Stx enzyme immunoassay (R-Biopharm), the latex agglutination assay (VTEC-RPLA; Denka Seiken, Coventry, United Kingdom), and Stx colony immunoblotting (Sifin). +, positive result; −, negative result. Identical results were obtained with all of the conventional assays for each strain.

^bImmuno-PCR detection response to various supernatant dilutions. +, PCR product present; −, PCR product absent; ND, not done.

^cSerotypes O40:H8 (three samples), O86:H⁻, and O_rough:HNT.

^dSerotype ONT (not typeable):H⁻.

^eSerotypes O91:H⁻ and ONT:H12.

^fSerotype ONT:H⁻.

^gStrain EDL933 serotype O157:H7.

^h—, no stx gene was detected.