Table 2. Identification of false negative colony on Petrifilm coliform count

Biochemical test	Colony number
	P20-3M-N1	P20-3M-N5	P22-3M-N3	P22-3M-N4	G13-3M-N4	G16-3M-N1	G16-3M-N4	G30-3M-N4	G30-3M-N5
Lactose broth	Gas (+)	Gas (+)	Gas (+)	Gas (+)	Gas (+)	Gas (+)	Gas (+)	Gas (+)	Gas (+)
Gram stain	negative	negative	negative	negative	negative	negative	negative	negative	negative
Catalase	+	+	+	+	+	+	+	+	+
Oxidase	-	-	-	-	-	-	-	-	-
Motility	+	+	+	+	+	+	+	+	+
ONPG	+	+	+	+	+	+	+	+	+
PCC1)	Red colony, gas(-)	Red colony, gas(-)	Red colony, gas(-)	Red colony, gas(-)	Red colony, gas(-)	Red colony, gas(-)	Red colony, gas(-)	Red colony, gas(-)	Red colony, gas(-)
SCC2)	Blue colony	Blue colony	Blue colony	Blue colony	Blue colony	Blue colony	Blue colony	Blue colony	Blue colony
API 20E	Escherichia hermannii	Escherichia hermannii	Pantoea spp. 2	Pantoea spp. 3	Pantoea spp. 3	Pantoea spp. 2	Pantoea spp. 1	Pantoea spp. 2	Pantoea spp. 2

¹⁾PCC: Petrifilm coliform count (incubation at 35℃ for 24 h)
²⁾SCC: Sanita-kun coliform count (incubation at 35℃ for 24 h)