TABLE 1.

E. coli strains and their tolerances to low pHs and organic acids

Strain	Serotype	Description and source	% Survivala
			pH 2	pH 3	Acetateb	Lactateb	Malateb	Citrateb
ATCC 35150	O157:H7	Clinical isolatec	0.40	75	39	0.01	68	66
ATCC 43895	O157:H7	Hamburger isolatec	0.02	64	79	0.08	51	67
505B	O157:H7	Beef isolated	0	4.1	1.8	<0.01	0.10	12
NCTC 12079	O157:H7	Clinical isolatee	0	0.69	0.08	0.01	0.01	0.10
30-2C4	O157:H7	Clinical isolate, salamid	1.5	87	100	6.0	85	94
C9490	O157:H7	Clinical isolate, “Jack-in-the-Box” hamburgerd	0	51	6.7	0.06	78	72
1267	O157:H7	Clinical isolatef	0.40	90	100	3.3	76	100
W2-2	O157:H7	Poultry isolated	0	15	2.0	<0.01	6.3	10
NCTC 10964	O157:K88a,c:H19	Isolate from piglete	0	89	34	0.20	77	84
NCTC 9001	O1:K1:H7	Clinical isolate, urinee	0	11	0.02	<0.0l	2.0	16
NCTC 10865	O20:K84:H26	Clinical isolatee	0	81	62	2.1	100	69
J1	Unknown	Clinical isolate, healthy volunteerg	0.02	28	15	0.05	2.1	86

^aExpressed as percentage of CFU per milliliter of inoculum (approximately 5 × 10⁹ CFU · ml⁻¹, diluted 1:1,000). Data are averages from at least two independent experiments and routinely varied by less than 30%. The limit of detection is 50 CFU ml⁻¹. 

^bUndissociated acid 50 mM added to TSB at pH 3. 

^cFrom the American Type Culture Collection, Manassas, Va. 

^dSupplied by M. P. Doyle, University of Georgia, Griffin. 

^eFrom the National Collection of Type Cultures, Public Health Laboratory Service, Colindale, United Kingdom. 

^fSupplied by F. Thomson-Carter, Scottish Reference Laboratory, Aberdeen, Scotland. 

^gSupplied by J. Glover, University of Aberdeen, Aberdeen, Scotland.