TABLE 1.

Strains of L. monocytogenes serotype 4b used in this study

Strain category (no. of strains)	PulseNet pattern designationa (no. of isolates)	PCR resultb
		4bSF7 and 4bSF18	4bSF149
ECIc (10)	GX6A16.0012,GX6A12.0007 (4)	+	+
	GX6A16.0291,GX6A12.0367 (1)
	GX6A16.0189,GX6A12.0697 (2)
	GX6A16.0003,GX6A12.0048 (1)
	GX6A16.0031,GX6A12.0426 (1)
	GX6A16.0031,GX6A12.0126 (1)
ECIId (8)	GX6A16.0002,GX6A12.0002 (2): E0	−	+
	GX6A16.0002,GX6A12.0003 (2): E1
	GX6A16.0002,GX6A12.0004 (2): E2
	GX6A16.0002,GX6A12.0057 (1): E3
	GX6A16.0016,GX6A12.0003 (1): E1
Pate outbreak (4)	GX6A16.0003,GX6A12.0048 (4)	+	+
Boston outbreak (1)	GX6A16.0003,GX6A12.0048 (1)	+	+
Other 4be (16)	G6XA16.0012,GX6A12.0007 (1)	+	+
	GX6A16.0031,GX6A12.0126 (1)
	GX6A16.0031,GX6A12.0247 (2)
	GX6A16.0031,GX6A12.0426 (3)
	GX6A16.0031,GX6A12.0696 (2)
	GX6A16.0320,GX6A12.0388 (3)
	NA (4)

^aPFGE patterns are reported with standard PulseNet nomenclature: GX6 = L. monocytogenes; A16 and A12 indicate AscI and ApaI restriction enzymes, respectively; five-digit number designations indicate sequentially assigned pattern numbers for each unique pattern in the PulseNet database. The number of isolates with a given PFGE pattern is given in parentheses. NA, not available.

^bPCR results obtained with primers designed for fragments 4bSF7, 4bSF18, and 4bSF149 (Table 2). +, expected amplicon obtained; −, no PCR product obtained.

^cIncluded three isolates each from the California (Mexican-style cheese), Canada (coleslaw), and Switzerland (soft cheese) outbreaks and one isolate from the pork tongue in aspic outbreak (France).

^dE₁, E₂, and E₃ are minor variations of the pattern labeled E₀.

^eSerotype 4b strains without known implication in outbreaks.