Determination of virulence and antibiotic resistance pattern of biofilm producing Listeria species isolated from retail raw milk

Table 1 Pathogenicity profiles of Listeria species isolated from buffalo and cow milk

Source of milk samples	Listeria species	Serotype	Pathogenicity profile
			CAMP (+/-) with S/R	PI-PLC	DLABN	DAPN	Anton’s eye test	Mice lethality	Chick-embryo lethality	Vero cell ingestion assay	Biofilm
			CAMP (+/-) with S/R	PI-PLC	DLABN	DAPN	Anton’s eye test	Mice lethality	Chick-embryo lethality	Vero cell ingestion assay	Microtiter plate assay	Christensen’s tube
(ATCC 7494)	monocytogenes	4	+/-	+	-	-	+	+	+	++	Strong (O.D. = 0.158)	Strong
Buffalo	monocytogenes	1	+/+	+	-	-	+	+	+	++	Strong (O.D. = 0.148)	Moderate
	innocua		-	-	+	+	-	-	-	-	Strong (O.D. = 0.167)	Strong
	seelegeri		-	-	+	+	-	-	-	-	Strong (O.D. = 0.144)	Moderate
	seelegeri		-	-	+	+	-	-	-	-	Strong (O.D. = 0.157)	Moderate
	welshemeri		-	-	+	+	-	-	-	-	Strong (O.D. = 0.145)	Weak
	welshemeri		-	-	+	+	-	-	-	-	Strong (O.D. = 0.141)	Weak
	grayi		-	-	+	+	-	-	-	-	Weak (O.D. = 0.0995)	Moderate
	grayi		-	-	+	+	-	-	-	-	Strong (O.D. = 0.134)	Moderate
Cow	monocytogenes	4	+/-	+	-	-	+	+	+	++	Strong (O.D. = 0.123)	Strong
	innocua		-	-	+	+	-	-	-	-	Strong (O.D. = 0.125)	Strong
	seelegeri		-	-	+	+	-	-	-	-	Weak (O.D. = 0.074)	Moderate
	seelegeri		-	-	+	+	-	-	-	-	Very Strong (O.D. = 0.231)	Moderate
	welshemeri		-	-	+	+	-	-	-	-	Strong (O.D. = 0.128)	Moderate
	welshemeri		-	-	+	+	-	-	-	-	Strong (O.D. = 0.121)	Moderate
	welshemeri		-	-	+	+	-	-	-	-	Strong (O.D. = 0.117)	Moderate
	L. grayi		-	-	+	+	-	-	-	-	Strong (O.D. = 0.173)	Weak

CAMP Christie, Atkins, Munch-Petersen test, S/R Staphylococcus aureus/Rhodococcus equi, PI-PLC phosphatidylinositol-specific phospholipase C, DLABN DL-alanine-b-naphthylamide HCl, DAPN D-alanine-p-nitroanilide, O.D. Optical Density, O.D. ₅₉₅ < 0.1 = Weak; O.D. ₅₉₅ ≤ 0.1 = Strong; O.D. ₅₉₅ > 1 = Very Strong