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

1998 ◽  
Vol 61 (2) ◽  
pp. 158-161 ◽  
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.

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

1997 ◽  
Vol 60 (12) ◽  
pp. 1478-1482 ◽  
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.

Effect of Acid Adaptation on Survival of Escherichia coli O157:H7 in Meat Decontamination Washing Fluids and Potential Effects of Organic Acid Interventions on the Microbial Ecology of the Meat Plant Environment

2002 ◽  
Vol 65 (1) ◽  
pp. 33-40 ◽  
Author(s):  
JOHN SAMELIS ◽  
JOHN N. SOFOS ◽  
PATRICIA A. KENDALL ◽  
GARY C. SMITH
Keyword(s):  
Escherichia Coli ◽  
Lactic Acid ◽  
Organic Acid ◽  
Microbial Ecology ◽  
Acid Tolerance ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
C Storage ◽  
Plant Environment ◽  
Wide Ph Range

The acid tolerance of Escherichia coli O157:H7 may be pH inducible. Correspondingly, organic acid meat decontamination washing fluids may enhance the establishment of acid-adapted E. coli O157:H7 strains in packing plants, especially in mixtures with water washings from meat that may be of sublethal pH. Acid-adapted and nonadapted cultures of a rifampin-resistant derivative of the acid-resistant E. coli O157:H7 strain ATCC 43895 were tested to evaluate their survival in meat-washing fluids over a wide pH range. The cultures were exposed (105 CFU/ml) to acidic (2% lactic acid, 2% acetic acid, or a mixture of the two with water washings at ratios of 1/1, 1/9, or 1/99 [vol/vol]) or nonacid (water) meat washings for up to 14 days at 4 or 10°C storage. E. coli O157:H7 survived in water washings, but the low storage temperatures and predominant natural microbiota synergistically inhibited its growth. Compared with acid-adapted populations, nonadapted populations displayed greater potential for survival and a tendency to initiate growth in water meat washings at 10°C. The pathogen survived in most of the acid washings throughout storage (14 days), sometimes with minimal population reductions. Overall, nonadapted populations declined faster than acid-adapted populations, while the declines increased as the acid concentration and temperature of storage increased and were more dramatic in lactate, compared to acetate, washings. Acid-containing washings were selective for growth of lactic acid bacteria and yeasts, indicating that organic acid treatments may alter the microbial ecology of meat plant environments and potentially that of the meat. These results should be considered when selecting decontamination technologies for meat.

Inactivation of Escherichia coli O157:H7, Salmonella enterica Serotype Enteritidis, and Listeria monocytogenes on Lettuce by Hydrogen Peroxide and Lactic Acid and by Hydrogen Peroxide with Mild Heat

2002 ◽  
Vol 65 (8) ◽  
pp. 1215-1220 ◽  
Author(s):  
CHIA-MIN LIN ◽  
SARAH S. MOON ◽  
MICHAEL P. DOYLE ◽  
KAY H. McWATTERS
Keyword(s):  
Escherichia Coli ◽  
Hydrogen Peroxide ◽  
Lactic Acid ◽  
Listeria Monocytogenes ◽  
Salmonella Enterica ◽  
Salmonella Enteritidis ◽  
Sensory Characteristics ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Log Reduction

Iceberg lettuce is a major component in vegetable salad and has been associated with many outbreaks of foodborne illnesses. In this study, several combinations of lactic acid and hydrogen peroxide were tested to obtain effective antibacterial activity without adverse effects on sensory characteristics. A five-strain mixture of Escherichia coli O157:H7, Salmonella enterica serotype Enteritidis, and Listeria monocytogenes was inoculated separately onto fresh-cut lettuce leaves, which were later treated with 1.5% lactic acid plus 1.5% hydrogen peroxide (H2O2) at 40°C for 15 min, 1.5% lactic acid plus 2% H2O2 at 22°C for 5 min, and 2% H2O2 at 50°C for 60 or 90 s. Control lettuce leaves were treated with deionized water under the same conditions. A 4-log reduction was obtained for lettuce treated with the combinations of lactic acid and H2O2 for E. coli O157:H7 and Salmonella Enteritidis, and a 3-log reduction was obtained for L. monocytogenes. However, the sensory characteristics of lettuce were compromised by these treatments. The treatment of lettuce leaves with 2% H2O2 at 50°C was effective not only in reducing pathogenic bacteria but also in maintaining good sensory quality for up to 15 days. A ≤4-log reduction of E. coli O157:H7 and Salmonella Enteritidis was achieved with the 2% H2O2 treatment, whereas a 3-log reduction of L. monocytogenes was obtained. There was no significant difference (P > 0.05) between pathogen population reductions obtained with 2% H2O2 with 60- and 90-s exposure times. Hydrogen peroxide residue was undetectable (the minimum level of sensitivity was 2 ppm) on lettuce surfaces after the treated lettuce was rinsed with cold water and centrifuged with a salad spinner. Hence, the treatment of lettuce with 2% H2O2 at 50°C for 60 s is effective in initially reducing substantial populations of foodborne pathogens and maintaining high product quality.

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