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.

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.

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.

Thermotolerance of Escherichia coli O157:H7 ATCC 43894, Escherichia coli B, and an rpoS-Deficient Mutant of Escherichia coliO157:H7 ATCC 43895 Following Exposure to 1.5% Acetic Acid

1998 ◽  
Vol 61 (9) ◽  
pp. 1184-1186 ◽  
Author(s):  
NICOLE C. WILLIAMS ◽  
STEVEN C. INGHAM
Keyword(s):  
Escherichia Coli ◽  
Acetic Acid ◽  
Heat Resistance ◽  
Acid Stress ◽  
Deficient Mutant ◽  
E Coli ◽  
Significant Difference ◽  
Stressed Cells ◽  
D Values ◽  
D Value

On a beef carcass, Escherichia coli may sequentially encounter acid- and heat-intervention steps. This study tested whether acid stress (1.5% [vol/vol] acetic acid, pH 4.0, 37°C, 15 min) would enhance subsequent heat resistance of E. coli. Initially, cells (E. coli O157:H7 ATCC 43894, nonpathogenic E. coli B [strain FRIK-124], and rpoS-deficient mutant 813-6 [derived from E. coli O157:H7 ATCC 43895]) were acid stressed and transferred to 54°C tiypticase soy broth (TSB), and survivors were immediately enumerated after at least three intervals of 12, 2, and 6 min, respectively, by plating. The ATCC 43894 and 813-6 strains survived the acid stress but strain FRIK-124 did not. Acid-stressed ATCC 43894 had significantly lower D values than the non-acid-stressed controls. Strain 813-6 had significantly lower D values than strain ATCC 43894, with no significant difference between acid-stressed and non-acid-stressed cells. In a second experiment, cooling of cells prior to plating resulted in an increased D value for acid-stressed ATCC 43894 cells, such that it was not significantly different from the D value for non-acid-stressed Controls. Using this protocol, there was no significant difference in D values between acid-stressed and non-acid-stressed ATCC 43894 cells in prewarmed TSB (54, 58, and 62°C), in prewarmed ground beef slurry (GBS; 58°C), or in TSB and GBS inoculated at 5°C and heated to 58°C. The acid stress tested does not enhance subsequent heat resistance of E. coli.

Escherichia coli O157:H7 Strains Isolated from Environmental Sources Differ Significantly in Acetic Acid Resistance Compared with Human Outbreak Strains†‡

2009 ◽  
Vol 72 (3) ◽  
pp. 503-509 ◽  
Author(s):  
DEOG-HWAN OH ◽  
YOUWEN PAN ◽  
ELAINE BERRY ◽  
MICHAEL COOLEY ◽  
ROBERT MANDRELL ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Acetic Acid ◽  
Acetic Acid Solution ◽  
Acid Resistance ◽  
Escherichia Coli O157 ◽  
Limited Information ◽  
E Coli ◽  
Log Reduction ◽  
Acetic Acid Resistance ◽  
Acidified Foods

A number of studies on the influence of acid on Escherichia coli O157:H7 have shown considerable strain differences, but limited information has been reported to compare the acid resistance based on the different sources of E. coli O157:H7 isolates. The purpose of this study was to determine the survival of E. coli O157:H7 strains isolated from five sources (foods, bovine carcasses, bovine feces, water, and human) in 400 mM acetic acid solutions under conditions that are typical of acidified foods. The isolates from bovine carcasses, feces, and water survived acetic acid treatment at pH 3.3 and 30°C significantly (P ≤ 0.05) better than did any food or human isolates. However, resistance to acetic acid significantly increased as temperature decreased to 15°C for a given pH, with little (P ≥ 0.05) difference among the different isolation sources. All groups of E. coli O157:H7 strains showed more than 1.8- to 4.5-log reduction at pH 3.3 and 30°C after 25 min. Significantly reduced (less than 1-log reduction) lethality for all E. coli O157:H7 strain mixtures was observed when pH increased to 3.7 or 4.3, with little difference in acetic acid resistance among the groups. The addition of glutamate to the acetic acid solution or anaerobic incubation provided the best protection compared with the above conditions for all groups of isolates. These results suggest that temperature, pH, and atmospheric conditions are key factors in establishing strategies for improving the safety of acidified foods.

scholarly journals Collaborative Regulation of Escherichia coli Glutamate-Dependent Acid Resistance by Two AraC-Like Regulators, GadX and GadW (YhiW)

2002 ◽  
Vol 184 (24) ◽  
pp. 7001-7012 ◽  
Author(s):  
Zhuo Ma ◽  
Hope Richard ◽  
Don L. Tucker ◽  
Tyrrell Conway ◽  
John W. Foster
Keyword(s):  
Escherichia Coli ◽  
Acid Stress ◽  
Acid Resistance ◽  
Negative Regulator ◽  
Receptor Protein ◽  
Growth Media ◽  
Infectious Dose ◽  
E Coli ◽  
Control Circuits

ABSTRACT An important feature of Escherichia coli pathogenesis is an ability to withstand extremely acidic environments of pH 2 or lower. This acid resistance property contributes to the low infectious dose of pathogenic E. coli species. One very efficient E. coli acid resistance system encompasses two isoforms of glutamate decarboxylase (gadA and gadB) and a putative glutamate:γ-amino butyric acid (GABA) antiporter (gadC). The system is subject to complex controls that vary with growth media, growth phase, and growth pH. Previous work has revealed that the system is controlled by two sigma factors, two negative regulators (cyclic AMP receptor protein [CRP] and H-NS), and an AraC-like regulator called GadX. Earlier evidence suggested that the GadX protein acts both as a positive and negative regulator of the gadA and gadBC genes depending on environmental conditions. New data clarify this finding, revealing a collaborative regulation between GadX and another AraC-like regulator called GadW (previously YhiW). GadX and GadW are DNA binding proteins that form homodimers in vivo and are 42% homologous to each other. GadX activates expression of gadA and gadBC at any pH, while GadW inhibits GadX-dependent activation. Regulation of gadA and gadBC by either regulator requires an upstream, 20-bp GAD box sequence. Northern blot analysis further indicates that GadW represses expression of gadX. The results suggest a control circuit whereby GadW interacts with both the gadA and gadX promoters. GadW clearly represses gadX and, in situations where GadX is missing, activates gadA and gadBC. GadX, however, activates only gadA and gadBC expression. CRP also represses gadX expression. It does this primarily by repressing production of sigma S, the sigma factor responsible for gadX expression. In fact, the acid induction of gadA and gadBC observed when rich-medium cultures enter stationary phase corresponds to the acid induction of sigma S production. These complex control circuits impose tight rein over expression of the gadA and gadBC system yet provide flexibility for inducing acid resistance under many conditions that presage acid stress.

scholarly journals Escherichia coli O157 : H7 glutamate- and arginine-dependent acid-resistance systems protect against oxidative stress during extreme acid challenge

Microbiology ◽  
2009 ◽  
Vol 155 (3) ◽  
pp. 805-812 ◽  
Author(s):  
Bradley L. Bearson ◽  
In Soo Lee ◽  
Thomas A. Casey
Keyword(s):  
Oxidative Stress ◽  
Escherichia Coli ◽  
Hydrogen Peroxide ◽  
Acid Stress ◽  
Acid Resistance ◽  
Dependent Manner ◽  
Bacterial Survival ◽  
E Coli ◽  
Stress Protection ◽  
Acid Challenge

Micro-organisms may simultaneously encounter multiple stresses in their environment. To investigate the protection that several known Escherichia coli O157 : H7 acid-resistance systems might provide against both oxidative and acid stress, the addition of diamide, a membrane-permeable thiol-specific oxidizing agent, or hydrogen peroxide were used concurrent with acid challenge at pH 2.5 to determine bacterial survival. The addition of either diamide or hydrogen peroxide decreased bacterial survival in a dose-dependent manner for E. coli O157 : H7 during challenge at pH 2.5 following overnight growth in LB MES pH 5.5 (acid-resistance system 1, AR1). In contrast, the presence of either glutamate or arginine during challenge provided significant protection against diamide- and hydrogen peroxide-induced oxidative stress during pH 2.5 acid challenge. Oxidative stress protection during acid challenge required gadC and adiA for the glutamate- (AR2) and arginine- (AR3) dependent acid-resistance systems, respectively. In addition, maximal protection against oxidative stress in the presence of glutamate required a low external pH (pH 2.5), since pH 5.5 did not protect. This study demonstrates that the glutamate- and arginine-dependent acid-resistance systems of E. coli O157 : H7 can simultaneously protect against oxidative stress during extreme acid challenge.

Effect of Acid Resistance of Escherichia coli O157:H7 on Efficacy of Buffered Lactic Acid To Decontaminate Chilled Beef Tissue and Effect of Modified Atmosphere Packaging on Survival of Escherichia coli O157:H7 on Red Meat

2001 ◽  
Vol 64 (11) ◽  
pp. 1661-1666 ◽  
Author(s):  
M. UYTTENDAELE ◽  
E. JOZWIK ◽  
A. TUTENEL ◽  
L. DE ZUTTER ◽  
J. URADZINSKI ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Lactic Acid ◽  
Modified Atmosphere Packaging ◽  
Acid Resistance ◽  
Red Meat ◽  
Modified Atmosphere ◽  
Escherichia Coli O157 ◽  
The Public ◽  
E Coli ◽  
Retail Cuts

The present study examined the effect of pH-independent acid resistance of Escherichia coli O157:H7 on efficacy of buffered lactic acid to decontaminate chilled beef tissue. A varied level of acid resistance was observed among the 14 strains tested. Eight strains were categorized as acid resistant, four strains as acid sensitive, and two strains demonstrated acid-inducible acid resistance. The survival of an acid-resistant (II/45/4) and acid-sensitive (IX/8/16) E. coli O157:H7 strain on chilled beef tissue treated with 1 and 2% buffered lactic acid, sterile water, or no treatment (control) was followed. A gradual reduction of E. coli O157:H7 was noticed during the 10 days of storage at 4°C for each of the treatments. Decontamination with 1 and 2% buffered lactic acid did not appreciably affect the pathogen. Differences in the pH-independent acid resistance of the strains had no effect on the efficacy of decontamination. The effect of modified atmosphere packaging (MAP) on survival of E. coli O157:H7 in red meat was also studied. MAP (40% CO2/60% N2) or vacuum did not significantly influence survival of E. coli O157:H7 on inoculated sliced beef (retail cuts) meat compared to packing in air. The relative small outgrowth of lactic acid bacteria during storage under vacuum for 28 days did not affect survival of E. coli O157:H7. Neither lactic acid decontamination nor vacuum or MAP packaging could enhance reduction of E. coli O157:H7 on beef, thus underlining the need for preventive measures to control the public health risk of E. coli O157:H7.

scholarly journals Products of the Escherichia coli Acid Fitness Island Attenuate Metabolite Stress at Extremely Low pH and Mediate a Cell Density-Dependent Acid Resistance

2007 ◽  
Vol 189 (7) ◽  
pp. 2759-2768 ◽  
Author(s):  
Aaron K. Mates ◽  
Atef K. Sayed ◽  
John W. Foster
Keyword(s):  
Escherichia Coli ◽  
Organic Acids ◽  
Regulatory Protein ◽  
Resistance Mechanism ◽  
Acid Stress ◽  
Acid Resistance ◽  
Cell Contact ◽  
Density Dependent ◽  
E Coli ◽  
Cell Densities

ABSTRACT Escherichia coli has an ability, rare among the Enterobacteriaceae, to survive extreme acid stress under various host (e.g., human stomach) and nonhost (e.g., apple cider) conditions. Previous microarray studies have exposed a cluster of 12 genes at 79 centisomes collectively called an acid fitness island (AFI). Four AFI genes, gadA, gadX, gadW, and gadE, were already known to be involved in an acid resistance system that consumes an intracellular proton through the decarboxylation of glutamic acid. However, roles for the other eight AFI gene products were either unknown or subject to conflicting findings. Two new aspects of acid resistance are described that require participation of five of the remaining eight AFI genes. YhiF (a putative regulatory protein), lipoprotein Slp, and the periplasmic chaperone HdeA protected E. coli from organic acid metabolites produced during fermentation once the external pH was reduced to pH 2.5. HdeA appears to handle protein damage caused when protonated organic acids diffuse into the cell and dissociate, thereby decreasing internal pH. In contrast, YhiF- and Slp-dependent systems appear to counter the effects of the organic acids themselves, specifically succinate, lactate, and formate, but not acetate. A second phenomenon was defined by two other AFI genes, yhiD and hdeD, encoding putative membrane proteins. These proteins participate in an acid resistance mechanism exhibited only at high cell densities (>108 CFU per ml). Density-dependent acid resistance does not require any demonstrable secreted factor and may involve cell contact-dependent activation. These findings further define the complex physiology of E. coli acid resistance.

Effects on the Microbiological Condition of Product of Decontaminating Treatments Routinely Applied to Carcasses at Beef Packing Plants†

2009 ◽  
Vol 72 (8) ◽  
pp. 1790-1801 ◽  
Author(s):  
C. O. GILL
Keyword(s):  
Escherichia Coli ◽  
Acetic Acid ◽  
Lactic Acid ◽  
Enteric Bacteria ◽  
Hot Water ◽  
Peroxyacetic Acid ◽  
E Coli ◽  
Beef Products ◽  
Vacuum Cleaning ◽  
Very High

Reports on the microbiological effects of decontaminating treatments routinely applied to carcasses at beef packing plants indicate that washing before skinning may reduce the numbers of enteric bacteria transferred from the hide to meat. Washing skinned carcasses and/or dressed sides can reduce the numbers of aerobes and Escherichia coli by about 1 log unit, and pasteurizing sides with steam or hot water can reduce their numbers by >1 or >2 log units, respectively. Spraying with 2% lactic acid, 2% acetic acid, or 200 ppm of peroxyacetic acid can reduce the numbers of aerobes and E. coli by about 1 log, but such treatments can be ineffective if solutions are applied in inadequate quantities or to meat surfaces that are wet after washing. Trimming and vacuum cleaning with or without spraying with hot water may be largely ineffective for improving the microbiological conditions of carcasses. When contamination of meat during carcass dressing is well controlled and carcasses are subjected to effective decontaminating treatments, the numbers of E. coli on dressed carcasses can be <1 CFU/1,000 cm2. However, meat can be recontaminated during carcass breaking with E. coli from detritus that persists in fixed and personal equipment. The adoption at all packing plants of the carcass-dressing procedures and decontaminating treatments used at some plants to obtain carcasses that meet a very high microbiological standard should be encouraged, and means for limiting recontamination of product during carcass breaking and for decontaminating trimmings and other beef products should be considered.

Interventions for the Reduction of Salmonella Typhimurium DT 104 and Non-O157:H7 Enterohemorrhagic Escherichia coli on Beef Surfaces†

2000 ◽  
Vol 63 (10) ◽  
pp. 1326-1332 ◽  
Author(s):  
CATHERINE N. CUTTER ◽  
MILDRED RIVERA-BETANCOURT
Keyword(s):  
Escherichia Coli ◽  
Acetic Acid ◽  
Lactic Acid ◽  
Salmonella Typhimurium ◽  
Enterohemorrhagic Escherichia Coli ◽  
Hot Water ◽  
Trisodium Phosphate ◽  
Meat Industry ◽  
E Coli

A study was conducted to determine if slaughter interventions currently used by the meat industry are effective against Salmonella Typhimurium definitive type 104 (DT 104) and two non-O157:H7 enterohemorrhagic Escherichia coli (EHEC). Three separate experiments were conducted by inoculating prerigor beef surfaces with a bovine fecal slurry containing Salmonella Typhimurium and Salmonella Typhimurium DT 104 (experiment 1), E. coli O157:H7 and E. coli O111:H8 (experiment 2), or E. coli O157:H7 and E. coli O26:H11 (experiment 3) and spray washing with water, hot water (72°C), 2% acetic acid, 2% lactic acid, or 10% trisodium phosphate (15 s, 125 ± 5 psi, 35 ± 2°C). Remaining bacterial populations were determined immediately after treatments (day 0), after 2 days of aerobic storage at 4°C, and after 7, 21, and 35 days of vacuum-packaged storage at 4°C. In addition to enumeration, confirmation of pathogen serotypes was performed for all treatments on all days. Of the interventions investigated, spray treatments with trisodium phosphate were the most effective, resulting in pathogen reductions of >3 log10 CFU/cm2, followed by 2% lactic acid and 2% acetic acid (>2 log10 CFU/cm2). Results also indicated that interventions used to reduce Salmonella Typhimurium on beef surfaces were equally effective against Salmonella Typhimurium DT 104 immediately after treatment and again after long-term, refrigerated, vacuum-packaged storage. Similarly, E. coli O111:H8 and E. coli O26:H11 associated with beef surfaces were reduced by the interventions to approximately the same extent as E. coli O157:H7 immediately after treatment and again after long-term, refrigerated, vacuum-packaged storage. It was also demonstrated that phenotypic characterization may not be sufficient to identify EHECs and that the organisms should be further confirmed with antibody- or genetic-based techniques. Based on these findings, interventions used by the meat industry to reduce Salmonella spp. and E. coli O157:H7 appear to be effective against DT 104 and other EHEC.

Sign in / Sign up

Export Citation Format

Share Document