TABLE 5.

Limit of detection of the STQC—comparison of ciprofloxacin induced and noninduced STEC broth cultures

Strain	Serotype	Subtype	Induced	Vero cell assay	Culture CFU/mla	STQC (CFU/test)b
DEC10B	O26:H11	Stx1a	No	Stx1	1.8 × 108	1.2 × 105
			Yes	Stx1	2.3 × 108	1.4 × 105
TW08101	O103:H2	Stx1a	No	Stx1	3.3 × 108	2.1 × 105
			Yes	Stx1	5.6 × 108	8.8 × 105
DEC8E	O111:H8	Stx1a	No	Stx1	9.0 × 108	1.4 × 106
			Yes	Stx1	3.5 × 107	2.2 × 104
DG131/3	O174:H8	Stx1c/2b	No	Stx1	2.2 × 108	6.3 × 105
			Yes	Stx1	0c	+
C296-09	O22:H8	Stx1c/2b	No	Stx1/2	1.2 × 108	9.4 × 105 Stx1, 7.5 × 105 Stx2
			Yes	Stx1/2	2.4 × 108	7.5 × 105 Stx1, 7.5 × 103 Stx2
G5506	O104:H21	Stx2a	No	Stx2	3.7 × 108	2.3 × 105
			Yes	Stx2	8.3 × 108	2.6 × 104
TW08023	O121:H19	Stx2a	No	Stx2	6.0 × 108	1.9 × 105
			Yes	Stx2	1.7 × 108	5.3 × 103
86-24	O157:H7	Stx2a	No	Stx2	8.7 × 108	5.4 × 105
			Yes	Stx2	2.1 × 108	1.3 × 103
EDL-933	O157:H7	Stx1a/2a	No	Stx1/2	6.7 × 108	1.0 × 106 Stx1, 5.2 × 105 Stx2
			Yes	Stx1/2	3.2 × 105	20 Stx1, 0.5 Stx2
94C	O48:H21	Stx1a/2a	No	Stx1/2	2.3 × 108	3.6 × 105 Stx1, 7.2 × 104 Stx2
			Yes	Stx1/2	0c	+ (Stx1, Stx2)

^aData representing CFU counts per milliliter are from the undiluted overnight GN broth culture.

^bData representing CFU counts per test correspond to the LOD determined after factoring in both the broth dilution and the additional dilution that occurs in performing the STQC testing procedure. For cases in which the CFU counts per milliliter could not be determined due to the lack of viable cells, a plus sign (+) indicates that toxin was detected by the assay.

^cAlthough ciprofloxacin was toxic to these strains, toxin was still produced and detected by both the Vero cell assay and the STQC.