TABLE 1.

Te^r and the presence of ter genes among EHEC O157:H7 and SF EHEC O157:NM strains

Serotype	Total no. of strains	SFb	No. (%) of strains with a characteristic
			Te MIC (μg/ml) in range of:				Robust growthc on:		No or strongly reduced growthd on:		ter genese
			256-1024	32-128	2-4	<1	CT-SMAC	LB-Te agar	CT-SMAC	LB-Te agar	Present	Absent
O157:H7	67	0	50 (74.6)f	16 (23.9)f	0 (0)	1 (1.5)	66 (98.5)	66 (98.5)	1 (1.5)	1 (1.5)	66 (98.5)g	1 (1.5)
O157:NMa	86	86	1 (1.2)f	2 (2.3)f	40 (46.5)	43 (50.0)	3 (3.5)	3 (3.5)	83 (96.5)	83 (96.5)	2h (2.3)g	84i (97.7)

^aNM, nonmotile.

^bSF, sorbitol fermentation as determined after overnight incubation on SMAC agar.

^cRobust growth, >1,000 colonies of normal size per plate.

^dNo growth, no colonies grown; strongly reduced growth, <10 colonies reduced in size present after overnight incubation.

^eAs determined by PCRs targeting terZ, terA, terB, terC, terD, terE, and terF (19); present, all genes investigated were present; absent, all genes investigated were absent.

^fTellurite resistance (Te^r): EHEC O157:H7 versus SF EHEC O157:NM, P < 0.000001 by the χ² test.

^gPresence of ter genes: EHEC O157:H7 versus SF EHEC O157:NM, P < 0.000001 by the χ² test.

^hTwo of three Te^r strains; the third was negative for ter genes.

ⁱ83 Te^s strains and 1 Te^r strain.