Acid tolerance of acid-adapted and nonacid-adapted Escherichia coli O157:H7 strains in beef decontamination runoff fluids or on beef tissue

The effects of lactic acid, acetic acid, and acidic calcium sulfate (ACS) on viability and subsequent acid tolerance of three strains of Escherichia coli O157:H7 were determined. Differences in tolerance to acidic environments were observed among strains, but the level of tolerance was not affected by the acidulant to which cells had been exposed. Cells of E. coli O157:H7 adapted to grow on tryptic soy agar acidified to pH 4.5 with ACS were compared to cells grown at pH 7.2 in the absence of ACS for their ability to survive after inoculation into ground beef treated with ACS, as well as untreated beef. The number of ACS-adapted cells recovered from ACS-treated beef was significantly (α = 0.05) higher than the number of control cells recovered from ACS-treated beef during the first 3 days of a 10-day storage period at 4°C, suggesting that ACS-adapted cells might be initially more tolerant than unadapted cells to reduced pH in ACS-treated beef. Regardless of treatment of ground beef with ACS or adaptation of E. coli O157:H7 to ACS before inoculating ground beef, the pathogen survived in high numbers.

Download Full-text

Acid Tolerance and Acid Shock Response of Escherichia coli O157:H7 and Non-O157:H7 Isolates Provide Cross Protection to Sodium Lactate and Sodium Chloride

Journal of Food Protection ◽

10.4315/0362-028x-61.2.158 ◽

1998 ◽

Vol 61 (2) ◽

pp. 158-161 ◽

Cited By ~ 42

Author(s):

DONNA MAE GARREN ◽

MARK A. HARRISON ◽

SCOTT M. RUSSELL

Keyword(s):

Escherichia Coli ◽

Lactic Acid ◽

Sodium Chloride ◽

Acid Tolerance ◽

Sodium Lactate ◽

Cross Protection ◽

Escherichia Coli O157 ◽

Strain Atcc ◽

Acid Shock ◽

Shock Response

The survival of Escherichia coli O157:H7 and non-O157:H7 due to an enhanced acid tolerance response (ATR), an enhanced acid shock response (ASR), or the stationary phase protective system when exposed to lactic acid and the resulting cross protection against increased concentrations of sodium chloride and sodium lactate was studied. Escherichia coli O157:H7 isolates (932 and E009) and a non-O157:H7 strain (ATCC 23716) were grown to stationary phase at 32°C and exposed to one of two treatments in an attempt to either acid shock or acid adapt the survivors. Acid-shocked cells were exposed to lactic acid at pH 4.0. Acid-adapted cells were first exposed to a pH of 5.5 and then an acid challenge of pH 4.0. Sodium lactate (10%, 20%, or 30%) or sodium chloride (5%, 10%, or 15%) were added to a minimal glucose medium after the acidification treatments. When acid shocked and acid adapted isolate 932 and strain ATCC 23716 tolerated the elevated levels of sodium lactate, and the strain ATCC 23716 tolerated the elevated levels of sodium chloride. Acid adaption allowed isolate 932 to tolerate higher levels of sodium chloride; however, the acid shocking did not provide the same protection. Neither of the acid treatments provided increased tolerance to sodium chloride for isolate E009. Evidence of cross protection against acid and sodium chloride or acid and sodium lactate in E. coli O157:H7 could point to a need for further evaluation of whether these combinations of preservation means are sufficient to control this pathogen.

Download Full-text

Escherichia coli O157:H7 survival, biofilm formation and acid tolerance under simulated slaughter plant moist and dry conditions

Food Microbiology ◽

10.1016/j.fm.2008.09.001 ◽

2009 ◽

Vol 26 (1) ◽

pp. 112-119 ◽

Cited By ~ 24

Author(s):

P SKANDAMIS ◽

J STOPFORTH ◽

L ASHTON ◽

I GEORNARAS ◽

P KENDALL ◽

...

Keyword(s):

Escherichia Coli ◽

Biofilm Formation ◽

Acid Tolerance ◽

Escherichia Coli O157 ◽

Dry Conditions

Download Full-text

Acid Tolerance of Acid-Adapted and Nonadapted Escherichia coli O157:H7 following Habituation (10°C) in Fresh Beef Decontamination Runoff Fluids of Different pH Values

Journal of Food Protection ◽

10.4315/0362-028x-67.4.638 ◽

2004 ◽

Vol 67 (4) ◽

pp. 638-645 ◽

Cited By ~ 13

Author(s):

JOHN SAMELIS ◽

PATRICIA KENDALL ◽

GARY C. SMITH ◽

JOHN N. SOFOS

Keyword(s):

Escherichia Coli ◽

Acid Tolerance ◽

Growth Potential ◽

Escherichia Coli O157 ◽

Sterile Water ◽

Water Control ◽

Term Survival ◽

Acid Adaptation ◽

E Coli ◽

Natural Flora

This study evaluated survival of Escherichia coli O157:H7 strain ATCC 43895 during exposure to pH 3.5 following its habituation for 2 or 7 days at 10°C in fresh beef decontamination waste runoff fluid mixtures (washings) containing 0, 0.02, or 0.2% of lactic or acetic acids. Meat washings and sterile water (control) were initially inoculated with approximately 5 log CFU/ml of acid- and nonadapted E. coli O157:H7 cells cultured (30°C, 24 h) in broth with and without 1% glucose, respectively. After 2 days, E. coli O157:H7 survivors from acetate washings (pH 3.7 to 4.7) survived at pH 3.5 better than E. coli O157:H7 survivors from lactate washings (pH 3.1 to 4.6), especially when the original inoculum was acid adapted. Also, although E. coli O157:H7 habituated in sterile water for 2 days survived well at pH 3.5, the corresponding survivors from nonacid water meat washings (pH 6.8) were rapidly killed at pH 3.5, irrespective of acid adaptation. After 7 days, E. coli O157:H7 survivors from acetate washings (pH 3.6 to 4.7) continued to resist pH 3.5, whereas those from lactate washings died off. This loss of acid tolerance by E. coli O157:H7 was due to either its low survival in 0.2% lactate washings (pH 3.1) or its acid sensitization in 0.02% lactate washings, in which a Pseudomonas-like natural flora showed extensive growth (>8 log CFU/ml) and the pH increased to 6.5 to 6.6. Acid-adapted E. coli O157:H7 populations habituated in water washings (pH 7.1 to 7.3) for 7 days continued to be acid sensitive, whereas nonadapted populations increased their acid tolerance, a response merely correlated with their slight (<1 log) growth at 10°C. These results indicate that the expression of high acid tolerance by acid-adapted E. coli O157:H7 can be maintained or enhanced in acid-diluted meat decontamination waste runoff fluids of pH levels that could permit long-term survival at 10°C. Previous acid adaptation, however, could reduce the growth potential of E. coli O157:H7 at 10°C in nonacid waste fluids of high pH and enriched in natural flora. These conditions might further induce an acid sensitization to stationary E. coli O157:H7 cells.

Download Full-text

Retention of Acid Tolerance and Acid Shock Responses of Escherichia coli O157:H7 and Non-O157:H7 Isolates

Journal of Food Protection ◽

10.4315/0362-028x-60.12.1478 ◽

1997 ◽

Vol 60 (12) ◽

pp. 1478-1482 ◽

Cited By ~ 20

Author(s):

DONNA MAE GARREN ◽

MARK A. HARRISON ◽

SCOTT M. RUSSELL

Keyword(s):

Escherichia Coli ◽

Lactic Acid ◽

Acid Tolerance ◽

Escherichia Coli O157 ◽

Adaptation Period ◽

E Coli ◽

Acid Shock ◽

Acidic Conditions ◽

Temperature Levels ◽

Over Time

Escherichia coli O157:H7 and non-O157:H7 survival due to induced acid tolerance or shock responses when exposed to lactic acid over time was studied. Induced acid tolerance or shock responses could allow pathogens, like E. coli O157:H7, to survive acidic conditions in foods during storage. Escherichia coli O157:H7 isolates 932 and E009 and a non-Ol57:H7 strain, 23716, were grown to stationary phase at 32°C and exposed to one of two treatments: acid shock or acid adaption. Acid-shocked cells were exposed to lactic acid at pH 3.5 or 4.0. Acid-adapted cells were exposed to pH 5.5 for an adaptation period and then exposed to an acid challenge of pH 3.5 or 4.0. Samples were incubated at either 25 or 32°C and survival of the isolates at 0, 3, 24, 48, 72, and 168 h (7 days), 336 h (14 days), and 504 h (21 days) was determined. All three isolates survived longer with larger populations at pH 4.0 and 25°C compared to the other treatments. In cases where a difference was observed in the two responses, acid-shocked cells had a higher survival rate (typically less than 2 logs) than acid-adapted cells in most cases. Isolate differences were observed at the two pH and temperature levels. Isolate 932 was the most resistant to the acidic conditions during the incubation period, E009 intermediate, and strain 23716 was the most sensitive.

Download Full-text

Escherichia coli O157: H7 Acid Tolerance and Survival in Apple Cider

Journal of Food Protection ◽

10.4315/0362-028x-57.6.460 ◽

1994 ◽

Vol 57 (6) ◽

pp. 460-464 ◽

Cited By ~ 229

Author(s):

LESLIE GARLAND MILLER ◽

CHARLES W. KASPAR

Keyword(s):

Escherichia Coli ◽

Sodium Benzoate ◽

Acid Tolerance ◽

Potassium Sorbate ◽

Escherichia Coli O157 ◽

Control Strain ◽

High Ph ◽

Apple Cider ◽

E Coli ◽

Log Reduction

The survival of two Escherichia coli O157:H7 (ATCC 43889 and 43895) and a control strain E. coli was compared in apple cider and in Trypticase soy broth (TSB) adjusted to low and high pH. The O157:H7 strains were detectable in apple cider after 14 to 21 days at 4°C, whereas the control strain could not be detected (> 4-log reduction) after 5 to 7 days. During the first 14 days of storage at 4°C, the levels of strain 43889 decreased by ~3 logs, whereas levels of strain 43895 were unchanged. Survival of O157:H7 strains and the control strain were unaffected by the presence of potassium sorbate or sodium benzoate, except in one instance. Sodium benzoate caused a decrease of 57% in strain 43895 after 21 days, but ~104 CFU/ml still remained. In TSB adjusted to pH 2, 3, 4, 11 or 12, strain 43895 was again the more resistant of the O157:H7 strains, both of which were more durable than the control strain. The O157:H7 strains (especially strain 43895) withstood pH 2 with a minimal drop in CPU after 24 h, whereas no viable organisms were detectable after this time at pH 12. At these extremes of pH, survival was generally greater at 4°C than at 25°C. Despite differences between strains, these results show that E. coli O157:H7 is exceptionally tolerant of acid pH.

Download Full-text

Influence of Incubation Conditions on Survival and Acid Tolerance Response of Escherichia coliO157:H7 and Non-O157:H7 Isolates Exposed to Acetic Acid

Journal of Food Protection ◽

10.4315/0362-028x-61.5.542 ◽

1998 ◽

Vol 61 (5) ◽

pp. 542-546 ◽

Cited By ~ 49

Author(s):

LESLYE BRUDZINSKI ◽

MARK A. HARRISON

Keyword(s):

Escherichia Coli ◽

Acetic Acid ◽

Organic Acids ◽

Adaptive System ◽

Acid Tolerance ◽

Effect Of Temperature ◽

Escherichia Coli O157 ◽

Acid Tolerance Response ◽

E Coli ◽

Tolerance Response

The increasing frequency of Escherichia coli O157:H7 outbreaks, especially in acidic foods, raises the concern of an acid tolerance response (ATR). Organic acids can be present in processed and preserved foods: shifts in the acid levels of foods due to these acids may allow E. coli to adapt and later tolerate pH levels that would normally inactivate the organism. The effect of temperature and agitation on the ATRs of three E. coli O157:H7 and two non-O157:H7 isolates were determined. Triggered at pH 5.0, the adaptive System of the ATR allowed for up to nearly 1,000-fold enhanced survival of E. coli O157:H7 cells in some cases compared to survival of nonadapted cells at pH 4.0. E. coli O157:H7 isolates revealed greater acid tolerance responses when incubated statically at 32°C, whereas the non-O157:H7 coli isolates exhibited a greater acid tolerance response with orbital agitation at 25°C. The magnitude of response changed over the incubation period.

Download Full-text

Augmentation of Killing of Escherichia coli O157 by Combinations of Lactate, Ethanol, and Low-pH Conditions

Applied and Environmental Microbiology ◽

10.1128/aem.65.3.1308-1311.1999 ◽

1999 ◽

Vol 65 (3) ◽

pp. 1308-1311 ◽

Cited By ~ 50

Author(s):

Sarah L. Jordan ◽

Jayne Glover ◽

Laura Malcolm ◽

Fiona M. Thomson-Carter ◽

Ian R. Booth ◽

...

Keyword(s):

Escherichia Coli ◽

Stationary Phase ◽

Acid Tolerance ◽

Low Ph ◽

Exponential Phase ◽

Escherichia Coli O157 ◽

Cytoplasmic Ph ◽

Ph Homeostasis ◽

Acid Tolerant ◽

Ph Conditions

ABSTRACT The acid tolerance of Escherichia coli O157:H7 strains can be overcome by addition of lactate, ethanol, or a combination of the two agents. Killing can be increased by as much as 4 log units in the first 5 min of incubation at pH 3 even for the most acid-tolerant isolates. Exponential-phase, habituated, and stationary-phase cells are all sensitive to incubation with lactate and ethanol. Killing correlates with disruption of the capacity for pH homeostasis. Habituated and stationary-phase cells can partially offset the effects of the lowering of cytoplasmic pH.

Download Full-text