Table 1.

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

StrainSerotypeDescription and source% Survivala
pH 2pH 3AcetatebLactatebMalatebCitrateb
ATCC 35150O157:H7Clinical isolatec 0.4075390.016866
ATCC 43895O157:H7Hamburger isolatec 0.0264790.085167
505BO157:H7Beef isolated 04.11.8<0.010.1012
NCTC 12079O157:H7Clinical isolatee 00.690.
30-2C4O157:H7Clinical isolate, salamid 1.5871006.08594
C9490O157:H7Clinical isolate, “Jack-in-the-Box” hamburgerd 0516.70.067872
1267O157:H7Clinical isolatef 0.40901003.376100
W2-2O157:H7Poultry isolated 0152.0<0.016.310
NCTC 10964O157:K88a,c:H19Isolate from piglete 089340.207784
NCTC 9001O1:K1:H7Clinical isolate, urinee 0110.02<0.0l2.016
NCTC 10865O20:K84:H26Clinical isolatee 081622.110069
J1UnknownClinical isolate, healthy volunteerg 0.0228150.052.186
  • a Expressed as percentage of CFU per milliliter of inoculum (approximately 5 × 109CFU · 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.

  • b Undissociated acid 50 mM added to TSB at pH 3.

  • c From the American Type Culture Collection, Manassas, Va.

  • d Supplied by M. P. Doyle, University of Georgia, Griffin.

  • e From the National Collection of Type Cultures, Public Health Laboratory Service, Colindale, United Kingdom.

  • f Supplied by F. Thomson-Carter, Scottish Reference Laboratory, Aberdeen, Scotland.

  • g Supplied by J. Glover, University of Aberdeen, Aberdeen, Scotland.