TABLE 3.

Change in properties characteristic of E. coli O157:H7 after incubation in water^a

Strain	Results before incubation							Incubating conditions	Results after incubation
	O157 O antigenicity		Orf2	PCR-VT1	PCR-VT2	Latex-VT1	Latex-VT2		O157 O antigenicity		Orf2	PCR-VT1	PCR-VT2	Latex-VT1	Latex-VT2
	Antiserum	Latex							Antiserum	Latex
A	+ (10/10)b	+ (10/10)	+	+	+	+	+	In PBS at 4°C (230 days)	+ (4/8) − (4/8)	+ (4/8) − (4/8)	+ (4/4) − (0/4)	+ (4/4) − (0/4)	+ (4/4) − (0/4)	+ (4/4) − (0/4)	+ (0/4) − (4/4)
								In DW at 18°C (277 days)	+ (0/3) − (3/3)	+ (0/3) − (3/3)	+ (3/3) − (0/3)	+ (3/3) − (0/3)	+ (3/3) − (0/3)	+ (3/3) − (0/3)	+ (0/3) − (3/3)
								In DW at 18°C (635 days)	+ (0/3) − (3/3)	+ (0/3) − (3/3)	+ (3/3) − (0/3)	+ (3/3) − (0/3)	+ (3/3) − (0/3)	+ (3/3) − (0/3)	+ (0/3) − (3/3)
B	+ (10/10)	+ (10/10)	+	−	+	−	+	In PBS at 18°C (230 days)	+ (13/34) − (21/34)	+ (13/34) − (21/34)	+ (21/21) − (0/21)	+ (0/21) − (21/21)	+ (21/21) − (0/21)	+ (0/21) − (21/21)	+ (21/21) − (0/21)
K	+ (10/10)	+ (10/10)	+	−	+	−	+	In PBS at 18°C (230 days)	+ (2/30) − (28/30)	+ (2/30) − (28/30)	+ (28/28) − (0/28)	+ (0/28) − (28/28)	+ (28/28) − (0/28)	+ (0/28) − (28/28)	+ (28/28) − (0/28)
Q	+ (10/10)	+ (10/10)	+	−	+	−	+	In PBS at 18°C (230 days)	+ (9/30) − (21/30)	+ (9/30) − (21/30)	+ (21/21) − (0/21)	+ (0/21) − (21/21)	+ (0/21) − (0/21)	+ (0/21) − (21/21)	+ (21/21) − (0/21)
S	+ (10/10)	+ (10/10)	+	+	+	+	+	In PBS at 18°C (230 days)	+ (20/30) − (10/30)	+ (20/30) − (10/30)	+ (10/10) − (0/10)	+ (10/10) − (0/10)	+ (10/10) − (0/10)	+ (10/10) − (0/10)	+ (10/10) − (0/10)

^aO157 O antigenicity, agglutination test for anti-O157 serum and a latex agglutination kit; Orf2, detection of the orf2 O157 lipopolysaccharide gene by PCR; PCR-VT1, detection of the VT1 gene by PCR; Latex-VT1: detection of VT1 using the reversed passive latex agglutination test; +, positive reaction; −, negative reaction. 

^bNumber of colonies with reactions/number of colonies tested.