Behavior of Acid-Adapted and Unadapted Escherichia coli O157:H7 When Exposed to Reduced pH Achieved with Various Organic Acids

1999 ◽  
Vol 62 (5) ◽  
pp. 451-455 ◽  
Author(s):  
JEE-HOON RYU ◽  
YUN DENG ◽  
LARRY R. BEUCHAT
Keyword(s):  
Escherichia Coli ◽  
Acetic Acid ◽  
Lactic Acid ◽  
Citric Acid ◽  
Organic Acids ◽  
Malic Acid ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Ph Values ◽  
Acid Ph

A study was done to determine if various organic acids differ in their inhibitory or lethal activity against acid-adapted and unadapted Escherichia coli O157:H7 cells. E. coli O157:H7 strain E0139, isolated from venison jerky, was grown in tryptic soy broth (TSB) and in TSB supplemented with 1% glucose (TSBG) for 18 h at 37°C, then plated on tryptic soy agar (TSA) acidified with malic, citric, lactic, or acetic acid at pH 5.4, 5.1, 4.8, 4.5, 4.2, and 3.9. Regardless of whether cells were grown in TSB or TSBG, visible colonies were not formed when plated on TSA acidified with acetic, lactic, malic, or citric acids at pH values of ≤5.4, ≤4.5, ≤4.2, or ≤4.2, respectively. Cells not adapted to reduced pH did not form colonies on TSA acidified with lactic acid (pH 3.9) or acetic acid (pH 3.9 and 4.2); however, a portion of acid-adapted cells remained viable on TSA containing lactic acid (pH 3.9) or acetic acid (pH 4.2) and could be recovered in TSB. Inactivation of acid-adapted cells was less than that of unadapted cells in TSB acidified at pH 3.9 with citric, lactic, or acetic acid and at pH 3.4 with malic acid. Significantly (P ≤ 0.05) higher numbers of acid-adapted cells, compared with unadapted cells, were detected 12 h after inoculation of TSB acidified with acetic acid at pH 3.9; in TSB containing lactic acid (pH 3.9), the number of acid-adapted cells was higher than the number of unadapted cells after 5 h. In TSB acidified at pH 3.9 with citric acid or pH 3.4 with malic acid, significantly higher numbers of acid-adapted cells survived. This study shows that organic acids differ in their inhibitory or lethal activity against acid-adapted and unadapted E. coli O157:H7 cells, and acid-adapted cells are more tolerant than unadapted cells when subsequently exposed to reduced pH caused by these acids.

Effect of pH, Acidulant, Time, and Temperature on the Growth and Survival of Listeria monocytogenes

1989 ◽  
Vol 52 (8) ◽  
pp. 571-573 ◽  
Author(s):  
KENT M. SORRELLS ◽  
DAVIN C. ENIGL ◽  
JOHN R. HATFIELD
Keyword(s):  
Antimicrobial Activity ◽  
Acetic Acid ◽  
Lactic Acid ◽  
Listeria Monocytogenes ◽  
Citric Acid ◽  
Hydrochloric Acid ◽  
Malic Acid ◽  
Incubation Temperature ◽  
Growth And Survival ◽  
Ph Values

The effect of different acids, pH, incubation time, and incubation temperature on the growth and survival of four strains of Listeria monocytogenes in tryptic soy broth was compared. Hydrochloric acid (HCl), acetic acid (AA), lactic acid (LA), malic acid (MA), and citric acid (CA) were used to acidify tryptic soy broth to pH values 4.4, 4.6, 4.8, 5.0, and 5.2 pH. Incubation times were 1, 3, 7, 14, and 28 d at 10, 25, and 35°C. The inhibition of L. monocytogenes in the presence of high acidity appears to be a function of acid and incubation temperature. Based on equal pH values, the antimicrobial activity is AA > LA > CA ≥ MA > HCl at all incubation times and temperatures. When based on equal molar concentration, the activity appeared to be CA ≥ MA > LA ≥ AA > HCl at 35 and 25°C, and MA > CA > AA ≥ LA > HCl at 10°C. Greatest antimicrobial activity occurred at 35°C. Greatest survival occurred at 10°C and greatest growth occurred at 25°C. Final pH of the medium was as low as 3.8 in HCl at 28 d. All strains grew well at pH values lower than the minimum previously reported (5.5–5.6).

Efficacy of Selected Acidulants in Pureed Green Beans Inoculated with Pathogens (Escherichia coli O157:H7 and Listeria monocytogenes)

2006 ◽  
Vol 69 (8) ◽  
pp. 1865-1869 ◽  
Author(s):  
AAKASH KHURANA ◽  
GEORGE B. AWUAH ◽  
BRADLEY TAYLOR ◽  
ELENA ENACHE
Keyword(s):  
Escherichia Coli ◽  
Acetic Acid ◽  
Listeria Monocytogenes ◽  
Titratable Acidity ◽  
Combined Effect ◽  
Escherichia Coli O157 ◽  
Green Beans ◽  
E Coli ◽  
Acid Ph ◽  
D Values

Studies were conducted to evaluate the combined effect of selected acidulants (acetic, citric, malic, and phosphoric acid) and heat on foodborne pathogens (Escherichia coli O157:H7 and Listeria monocytogenes) in pureed green beans. To establish a consistent reference point for comparison, the molar concentrations of the acids remained constant while the acid-to-puree ratio, titratable acidity, and undissociated acid were either measured or calculated for a target acidified green beans at a pH of 3.8, 4.2, and 4.6. The D-values at 149°F were used as the criteria for acid efficacy. Generally, acetic acid (puree, pH 3.8 and 4.2) represented the most effective acid with comparatively low D-values irrespective of the target microorganism. A 10-s heating at 149°F inactivated approximately 106 CFU/ml of E. coli O157:H7 in pureed beans at pH 3.8. The efficacy of acetic acid is likely related to the elevated percent titratable acidity, undissociated acid, and acid-to-puree ratio. The effectiveness (which in this study represents the combined effect of acid and heat) of the remaining acids (citric, malic, and phosphoric) at puree pH values of 3.8 and 4.2 were statistically insignificant (α = 0.05). Surprisingly, acetic acid (puree, pH 4.6) appeared to be the least effective as compared to the other acids tested (citric, malic, and phosphoric) especially on E. coli O157:H7 cells, while L. monocytogenes had a similar resistance to all acids at puree pH 4.6. With the exception of citric acid (pH 3.8), acetic acid (pH 4.6), and malic acid (pH 3.8 and 4.6), which were statistically insignificant (P > 0.05), the D-values for L. monocytogenes were statistically different (P ≤ 0.05) and higher than the D-values for E. coli under similar experimental conditions. A conservative process recommendation (referred to as the “safe harbor” process) was found sufficient and applicable to pureed green beans for the pH range studied.

Validation of a Lactic Acid– and Citric Acid–Based Antimicrobial Product for the Reduction of Escherichia coli O157:H7 and Salmonella on Beef Tips and Whole Chicken Carcasses

2009 ◽  
Vol 72 (10) ◽  
pp. 2208-2211 ◽  
Author(s):  
A. M. LAURY ◽  
M. V. ALVARADO ◽  
G. NACE ◽  
C. Z. ALVARADO ◽  
J. C. BROOKS ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Lactic Acid ◽  
Citric Acid ◽  
External Surface ◽  
Escherichia Coli O157 ◽  
Water Control ◽  
E Coli ◽  
Pathogen Load ◽  
Control Samples ◽  
Spray Treatment

The objectives of this study were to determine the effects of a lactic acid– and citric acid–based antimicrobial product on the reduction of Salmonella on whole broiler carcasses during processing and the reduction of Salmonella and Escherichia coli O157:H7 on beef trim. Freshly harvested broiler carcasses were inoculated with an inoculum of Salmonella strains to yield a 105 CFU/ml pathogen load on the surface of the carcass. The beef tips were inoculated as well with an inoculum of either E. coli O157:H7 or Salmonella to yield 104 CFU/100 cm2. After 30 min for attachment, the broiler carcasses were treated with Chicxide applied for 5 s via a spray or immersed in Chicxide for 5, 10, or 20 s. Broiler carcasses were rinsed in poultry rinse bags with 400 ml of Butterfield's phosphate buffer in which Salmonella was enumerated from the diluents and Butterfield's phosphate. Chicxide significantly reduced Salmonella by 1.3 log CFU/ml with spray treatment and 2.3 log CFU/ml for all dip treatments. Following 30 min of attachment, the beef tips were placed into a spray cabinet with either Beefxide or sterilized water (control) and sprayed at 1 ft/2.5 s chain speed at 40 lb/in2. The external surface of each beef tip was swabbed (100 cm2) to determine pathogen loads. Beefxide significantly reduced E. coli O157:H7 by 1.4 log CFU/100 cm2 and Salmonella by 1.1 log CFU/100 cm2 (P < 0.05) compared with the control samples.

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

1998 ◽  
Vol 61 (5) ◽  
pp. 542-546 ◽  
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.

Synergistic Antilisterial Effects of Mixtures of Lysozyme and Organic Acids

2016 ◽  
Vol 79 (12) ◽  
pp. 2184-2189 ◽  
Author(s):  
MYEONGGEUN OH ◽  
JOONGJAE LEE ◽  
YOONHWA JEONG ◽  
MISOOK KIM
Keyword(s):  
Acetic Acid ◽  
Lactic Acid ◽  
Citric Acid ◽  
Organic Acids ◽  
Succinic Acid ◽  
Malic Acid ◽  
Synergistic Effects ◽  
The Other ◽  
Food Preservative ◽  
Time Kill

ABSTRACT We investigated the synergistic effects of lysozyme combined with organic acids to inhibit the growth of Listeria monocytogenes. The antilisterial effects of the combination of lysozyme and acetic acid, citric acid, lactic acid, malic acid, or succinic acid were evaluated using the checkerboard method and time-kill assay. The MIC was 25,000 mg/liter for lysozyme, 625 mg/liter for acetic acid, and 1,250 mg/liter for the other acids. The MBC was 10,000 mg/liter for all of the tested organic acids. The combination of lysozyme and each organic acid showed synergistic effects via the checkerboard method; however, the time-kill assay showed synergistic effects for only three combinations of 1,250 mg/liter lysozyme with succinic acid (312 and 625 mg/liter) or malic acid (625 mg/liter). The results of this study indicate that the combination of lysozyme and malic acid or succinic acid can be effectively used as a food preservative to control L. monocytogenes.

Effects of Bentonite Clarificants on Organic Acids Contents in Red Wine during Clarification

2011 ◽  
Vol 194-196 ◽  
pp. 802-805
Author(s):  
Zhan Sheng Wu ◽  
Xi Fang Sun ◽  
Chun Li
Keyword(s):  
Hydrogen Bond ◽  
Acetic Acid ◽  
Lactic Acid ◽  
Citric Acid ◽  
Organic Acids ◽  
Succinic Acid ◽  
Tartaric Acid ◽  
Malic Acid ◽  
Red Wine ◽  
Titratable Acidity

Effects of different bentonite clarificants on the main organic acids contents in wine were investigated during the clarification process. Citric acid (CA) concentration changed slightly during the first day with average elimination ratio (AER) of 0.57%, and tartaric acid (TA), malic acid (MA), lactic acid (LA) and succinic acid (SA) were varied with AER of 12.39%, 9.80%, 7.27% and 6.27%, respectively, while acetic acid (AA) has the biggest AER of 15.42%. The pH and titratable acidity were significantly dependent on the variation of CA and TA. The –OH group in organic acids could be combined with –Si-O or –AlO groups in bentonite surface by hydrogen bond, which could caused the decrease in concentration various organic acids.

scholarly journals Survival or Growth of Escherichia coli O157:H7 in a Model System of Fresh Meat Decontamination Runoff Waste Fluids and Its Resistance to Subsequent Lactic Acid Stress

2005 ◽  
Vol 71 (10) ◽  
pp. 6228-6234 ◽  
Author(s):  
John Samelis ◽  
John N. Sofos ◽  
Patricia A. Kendall ◽  
Gary C. Smith
Keyword(s):  
Escherichia Coli ◽  
Acetic Acid ◽  
Lactic Acid ◽  
Acid Stress ◽  
Acid Resistance ◽  
Fresh Meat ◽  
Sterile Saline ◽  
E Coli ◽  
Acid Ph ◽  
Natural Flora

ABSTRACT A potential may exist for survival of and resistance development by Escherichia coli O157:H7 in environmental niches of meat plants applying carcass decontamination interventions. This study evaluated (i) survival or growth of acid-adapted and nonadapted E. coli O157:H7 strain ATCC 43895 in acetic acid (pH 3.6 ± 0.1) or in water (pH 7.2 ± 0.2) fresh beef decontamination runoff fluids (washings) stored at 4, 10, 15, or 25°C and (ii) resistance of cells recovered from the washings after 2 or 7 days of storage to a subsequent lactic acid (pH 3.5) stress. Corresponding cultures in sterile saline or in heat-sterilized water washings were used as controls. In acetic acid washings, acid-adapted cultures survived better than nonadapted cultures, with survival being greatest at 4°C and lowest at 25°C. The pathogen survived without growth in water washings at 4 and 10°C, while it grew by 0.8 to 2.7 log cycles at 15 and 25°C, and more in the absence of natural flora. E. coli O157:H7 cells habituated without growth in water washings at 4 or 10°C were the most sensitive to pH 3.5, while cells grown in water washings at 15 or 25°C were relatively the most resistant, irrespective of previous acid adaptation. Resistance to pH 3.5 of E. coli O157:H7 cells habituated in acetic acid washings for 7 days increased in the order 15°C > 10°C > 4°C, while at 25°C cells died off. These results indicate that growth inhibition by storage at low temperatures may be more important than competition by natural flora in inducing acid sensitization of E. coli O157:H7 in fresh meat environments. At ambient temperatures in meat plants, E. coli O157:H7 may grow to restore acid resistance, unless acid interventions are applied to inhibit growth and minimize survival of the pathogen. Acid-habituated E. coli O157:H7 at 10 to 15°C may maintain a higher acid resistance than when acid habituated at 4°C. These responses should be evaluated with fresh meat and may be useful for the optimization of decontamination programs and postdecontamination conditions of meat handling.

Inactivation of Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella Typhimurium with Compounds Available in Households

2009 ◽  
Vol 72 (6) ◽  
pp. 1201-1208 ◽  
Author(s):  
HUA YANG ◽  
PATRICIA A. KENDALL ◽  
LYDIA MEDEIROS ◽  
JOHN N. SOFOS
Keyword(s):  
Escherichia Coli ◽  
Hydrogen Peroxide ◽  
Acetic Acid ◽  
Listeria Monocytogenes ◽  
Citric Acid ◽  
Salmonella Typhimurium ◽  
Initial Temperature ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Log Reduction

Solutions of selected household products were tested for their effectiveness against Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella Typhimurium. Hydrogen peroxide (1.5 and 3%), vinegar (2.5 and 5% acetic acid), baking soda (11, 33, and 50% sodium bicarbonate), household bleach (0.0314, 0.0933, and 0.670% sodium hypochlorite), 5% acetic acid (prepared from glacial acetic acid), and 5% citric acid solutions were tested against the three pathogens individually (five-strain composites of each, 108 CFU/ml) by using a modified AOAC International suspension test at initial temperatures of 25 and 55°C for 1 and 10 min. All bleach solutions (pH 8.36 to 10.14) produced a >5-log reduction of all pathogens tested after 1 min at 25°C, whereas all baking soda solutions (pH 7.32 to 7.55) were ineffective (<1-log reduction) even after 10 min at an initial temperature of 55°C. After 1 min at 25°C, 3% hydrogen peroxide (pH 2.75) achieved a >5-log reduction of both Salmonella Typhimurium and E. coli O157:H7, whereas undiluted vinegar (pH 2.58) had a similar effect only against Salmonella Typhimurium. Compared with 1 min at 25°C, greater reductions of L. monocytogenes (P < 0.05) were obtained with all organic acid and hydrogen peroxide treatments after 10 min at an initial temperature of 55°C. The efficacies of household compounds against all tested pathogens decreased in the following order: 0.0314% sodium hypochlorite > 3% hydrogen peroxide > undiluted vinegar and 5% acetic acid > 5% citric acid > baking soda (50% sodium bicarbonate). The sensitivity of the tested pathogens to all tested household compounds followed the sequence of Salmonella Typhimurium > E. coli O157: H7 > L. monocytogenes.

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.

Mitigating the Antimicrobial Activities of Selected Organic Acids and Commercial Sanitizers with Various Neutralizing Agents

2011 ◽  
Vol 74 (5) ◽  
pp. 820-825 ◽  
Author(s):  
YOEN JU PARK ◽  
JINRU CHEN
Keyword(s):  
Escherichia Coli ◽  
Acetic Acid ◽  
Lactic Acid ◽  
Organic Acids ◽  
Shiga Toxin ◽  
Room Temperature ◽  
Sodium Thiosulfate ◽  
Antimicrobial Activities ◽  
Phosphate Buffered Saline ◽  
Lactic Acids

This study was conducted to evaluate the abilities of five neutralizing agents, Dey-Engley (DE) neutralizing broth (single or double strength), morpholinepropanesulfonic acid (MOPS) buffer, phosphate-buffered saline (PBS), and sodium thiosulfate buffer, in mitigating the activities of acetic or lactic acid (2%) and an alkaline or acidic sanitizer (a manufacturer-recommended concentration) againt the cells of Shiga toxin–producing Escherichia coli (STEC; n = 9). To evaluate the possible toxicity of the neutralizing agents to the STEC cells, each STEC strain was exposed to each of the neutralizing agents at room temperature for 10 min. Neutralizing efficacy was evaluated by placing each STEC strain in a mixture of sanitizer and neutralizer under the same conditions. The neutralizing agents had no detectable toxic effect on the STEC strains. PBS was least effective for neutralizing the activity of selected organic acids and sanitizers. Single-strength DE and sodium thiosulfate neutralized the activity of both acetic and lactic acids. MOPS buffer neutralized the activity of acetic acid and lactic acid against six and five STEC strains, respectively. All neutralizing agents, except double-strength DE broth, had a limited neutralizing effect on the activity of the commercial sanitizers used in the study. The double-strength DE broth effectively neutralized the activity of the two commercial sanitizers with no detectable toxic effects on STEC cells.

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