Inactivation of Escherichia coli O157:H7 and Salmonella by Gamma Irradiation of Alfalfa Seed Intended for Production of Food Sprouts†

2003 ◽  
Vol 66 (2) ◽  
pp. 175-181 ◽  
Author(s):  
DONALD W. THAYER ◽  
KATHLEEN T. RAJKOWSKI ◽  
GLENN BOYD ◽  
PETER H. COOKE ◽  
DOUGLAS S. SOROKA
Keyword(s):  
Escherichia Coli ◽  
Moisture Content ◽  
Water Activity ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Alfalfa Seed ◽  
D Values ◽  
Different Sources ◽  
D Value ◽  
Alfalfa Seeds

Inonizing irradiation was determined to be a suitable method for the inactivation of Salmonella and Escherichia coli O157:H7 on alfalfa seed to be used in the production of food sprouts. The radiation D (dose resulting in a 90% reduction of viable CFU) values for the inactivation of Salmonella and E. coli O157:H7 on alfalfa seeds were higher than the D-values for their inactivation on meat or poultry. The average D-value for the inactivation of Salmonella on alfalfa seeds was 0.97 ± 0.03 kGy; the D-values for cocktails of meat isolates and for vegetable-associated isolates were not significantly different. The D-values for nonoutbreak and outbreak isolates of E. coli O157:H7 on alfalfa seeds were 0.55 ± 0.01 and 0.60 ± 0.01 kGy, respectively. It was determined that the relatively high D-values were not due to the low moisture content or the low water activity of the seed. The D-values for Salmonella on alfalfa seeds from two different sources did not differ significantly, even though there were significant differences in seed size and water activity. The increased moisture content of the seed after artificial inoculation did not significantly alter the D-value for the inactivation of Salmonella. The results of this study demonstrate that 3.3- and 2-log inactivations can be achieved with a 2-kGy dose of ionizing radiation, which will permit satisfactory commercial yields of sprouts from alfalfa seed contaminated with E. coli O157:H7 and Salmonella, respectively.

Thermal Inactivation of Escherichia coli O157: H7, Salmonella senftenberg, and Enzymes with Potential as Time-Temperature Indicators in Ground Beef

1997 ◽  
Vol 60 (5) ◽  
pp. 471-475 ◽  
Author(s):  
ALICIA ORTA-RAMIREZ ◽  
JAMES F. PRICE ◽  
YIH-CHIH HSU ◽  
GIRIDARAN J. VEERAMUTHU ◽  
JAMIE S. CHERRY-MERRITT ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Thermal Inactivation ◽  
Ground Beef ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Triose Phosphate ◽  
Beef Products ◽  
Z Value ◽  
D Values ◽  
Salmonella Senftenberg

The USDA has established processing schedules for beef products based on the destruction of pathogens. Several enzymes have been suggested as potential indicators of heat processing. However, no relationship between the inactivation rates of these enzymes and those of pathogenic microorganisms has been determined. Our objective was to compare the thermal inactivation of Escherichia coli O157:H7 and Salmonella senftenberg to those of endogenous muscle proteins. Inoculated and noninoculated ground beef samples were heated at four temperatures for predetermined intervals of time in thermal-death-time studies. Bacterial counts were determined and enzymes were assayed for residual activity. The D values for E. coli O157:H7 were 46.10, 6.44, 0.43, and 0.12 min at 53, 58, 63, and 68°C, respectively, with a z value of 5.60°C. The D values for S. senftenberg were 53.00, 15.17, 2.08, and 0.22 min at 53, 58, 63, and 68°C, respectively, with a z value of 6.24°C. Apparent D values at 53, 58, 63, and 68°C were 352.93, 26.31, 5.56, and 3.33 min for acid phosphatase; 6968.64, 543.48, 19.61, and 1.40 min for lactate dehydrogenase; and 3870.97, 2678.59, 769.23, and 42.92 min for peroxidase; with z values of 7.41,3.99, and 7.80°C, respectively. Apparent D values at 53, 58, 63, and 66°C were 325.03, 60.07, 3.07, and 1.34 min for phosphoglycerate mutase; 606.72, 89.86, 4.40, and 1.28 min for glyceraldehyde-3-phosphate dehydrogenase; and 153.06, 20.13, 2.25, and 0.74 min for triose phosphate isomerase; with z values of 5.18, 4.71, and 5.56°C, respectively. The temperature dependence of triose phosphate isomerase was similar to those of both E. coli O157 :H7 and S. senftenberg, suggesting that this enzyme could be used as an endogenous time-temperature indicator in beef products.

Chemical and Irradiation Treatments for Killing Escherichia coli O157:H7 on Alfalfa, Radish, and Mung Bean Seeds

2003 ◽  
Vol 66 (5) ◽  
pp. 767-774 ◽  
Author(s):  
M. L. BARI ◽  
E. NAZUKA ◽  
Y. SABINA ◽  
S. TODORIKI ◽  
K. ISSHIKI
Keyword(s):  
Escherichia Coli ◽  
Heat Treatment ◽  
Mung Bean ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Chemical Treatments ◽  
Dry Heat ◽  
Pathogen Populations ◽  
Dry Heat Treatment ◽  
Alfalfa Seeds

In this study, the effectiveness of dry-heat treatment in combination with chemical treatments (electrolyzed oxidizing [EO] water, califresh-S, 200 ppm of active chlorinated water) with and without sonication in eliminating Escherichia coli O157:H7 on laboratory-inoculated alfalfa, radish, and mung bean seeds was compared with that of dry-heat treatment in combination with irradiation treatment. The treatment of mung bean seeds with EO water in combination with sonication followed by a rinse with sterile distilled water resulted in reductions of approximately 4.0 log10 CFU of E. coli O157:H7 per g, whereas reductions of ca. 1.52 and 2.64 log10 CFU/g were obtained for radish and alfalfa seeds. The maximum reduction (3.70 log10 CFU/g) for mung bean seeds was achieved by treatment with califresh-S and chlorinated water (200 ppm) in combination with sonication and a rinse. The combination of dry heat, hot EO water treatment, and sonication was able to eliminate pathogen populations on mung bean seeds but was unable to eliminate the pathogen on radish and alfalfa seeds. Other chemical treatments used were effective in greatly reducing pathogen populations on radish and alfalfa seeds without compromising the quality of the sprouts, but these treatments did not result in the elimination of pathogens from radish and alfalfa seeds. Moreover, a combination of dry-heat and irradiation treatments was effective in eliminating E. coli O157:H7 on laboratory-inoculated alfalfa, radish, and mung bean seeds. An irradiation dose of 2.0 kGy in combination with dry heat eliminated E. coli O157:H7 completely from alfalfa and mung bean seeds, whereas a 2.5-kGy dose of irradiation was required to eliminate the pathogen completely from radish seeds. Dry heat in combination with irradiation doses of up to 2.0 kGy did not unacceptably decrease the germination percentage for alfalfa seeds or the length of alfalfa sprouts but did decrease the lengths of radish and mung bean sprouts.

Carvacrol and Cinnamaldehyde Facilitate Thermal Destruction of Escherichia coli O157:H7 in Raw Ground Beef†

2008 ◽  
Vol 71 (8) ◽  
pp. 1604-1611 ◽  
Author(s):  
VIJAY K. JUNEJA ◽  
MENDEL FRIEDMAN
Keyword(s):  
Escherichia Coli ◽  
Ground Beef ◽  
Inactivation Kinetics ◽  
Escherichia Coli O157 ◽  
Internal Temperature ◽  
Circulating Water ◽  
Critical Control Points ◽  
Thermal Death ◽  
D Values ◽  
D Value

The heat resistance of a four-strain mixture of Escherichia coli O157:H7 in raw ground beef in both the absence and presence of the antimicrobials carvacrol and cinnamaldehyde was tested at temperatures ranging from 55 to 62.5°C. Inoculated meat packaged in bags was completely immersed in a circulating water bath, cooked for 1 h to an internal temperature of 55, 58, 60, or 62.5°C, and then held for predetermined lengths of time ranging from 210 min at 55°C to 5 min at 62.5°C. The surviving bacteria were enumerated by spiral plating onto tryptic soy agar overlaid with sorbitol MacConkey agar. Inactivation kinetics of the pathogens deviated from first-order kinetics. D-values (time for the bacteria to decrease by 90%) in the control beef ranged from 63.90 min at 55°C to 1.79 min at 62.5°C. D-values determined by a logistic model ranged from 43.18 min (D1, the D-value of a major population of surviving cells) and 89.84 min (D2, the D-value of a minor subpopulation) at 55°C to 1.77 (D1) and 0.78 min (D2) at 62.5°C. The thermal death times suggested that to achieve a 4-D reduction, contaminated processed ground beef should be heated to an internal temperature of 60°C for at least 30.32 min. Significantly increased sensitivity to heat (P < 0.05) was observed with the addition and/or increasing levels of carvacrol or cinnamaldehyde from 0.5 to 1.0%. The observed thermal death times may facilitate the design of acceptance limits at critical control points for ground beef at lower times and temperatures of heating.

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.

Efficacy of Chemical Treatments in Eliminating Salmonella and Escherichia coli O157:H7 on Scarified and Polished Alfalfa Seeds

2001 ◽  
Vol 64 (10) ◽  
pp. 1489-1495 ◽  
Author(s):  
SARAH L. HOLLIDAY ◽  
ALAN J. SCOUTEN ◽  
LARRY R. BEUCHAT
Keyword(s):  
Escherichia Coli ◽  
Chemical Treatment ◽  
Organic Material ◽  
Pathogenic Bacteria ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Mechanical Abrasion ◽  
Chemical Treatments ◽  
The Impact ◽  
Alfalfa Seeds

Alfalfa seeds are sometimes subjected to a scarification treatment to enhance water uptake, which results in more rapid and uniform germination during sprout production. It has been hypothesized that this mechanical abrasion treatment diminishes the efficacy of chemical treatments used to kill or remove pathogenic bacteria from seeds. A study was done to compare the effectiveness of chlorine (20,000 ppm), H2O2 (8%), Ca(OH)2 (1%), Ca(OH)2 (1%) plus Tween 80 (1%), and Ca(OH)2 (1%) plus Span 20 (1%) treatments in killing Salmonella and Escherichia coli O157:H7 inoculated onto control, scarified, and polished alfalfa seeds obtained from two suppliers. The influence of the presence of organic material in the inoculum carrier on the efficacy of sanitizers was investigated. Overall, treatment with 1% Ca(OH)2 was the most effective in reducing populations of the pathogens. Reduction in populations of pathogens on seeds obtained from supplier 1 indicate that chemical treatments are less efficacious in eliminating the pathogens on scarified seeds compared to control seeds. However, the effectiveness of chemical treatment in removing Salmonella and E. coli O157:H7 from seeds obtained from supplier 2 was not markedly affected by scarification or polishing. The presence of organic material in the inoculum carrier did not have a marked influence on the efficacy of chemicals in reducing populations of test pathogens. Additional lots of control, scarified, and polished alfalfa seeds of additional varieties need to be tested before conclusions can be drawn concerning the impact of mechanical abrasion on the efficacy of chemical treatment in removing or killing Salmonella and E. coli O157:H7.

Survival of Escherichia coli O157:H7 in Full- and Reduced-Fat Pepperoni after Manufacture of Sticks, Storage of Slices at 4°C or 21°C under Air and Vacuum, and Baking of Slices on Frozen Pizza at 135, 191 and 246°C

1998 ◽  
Vol 61 (4) ◽  
pp. 383-389 ◽  
Author(s):  
NANCY G. FAITH ◽  
RACHEL K. WIERZBA ◽  
ANNE M. IHNOT ◽  
ANN M. ROERING ◽  
TIMOTHY D. LORANG ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Relative Humidity ◽  
Starter Culture ◽  
Escherichia Coli O157 ◽  
Protein Ratio ◽  
Direct Plating ◽  
E Coli ◽  
Reduced Fat ◽  
Log10 Unit ◽  
D Values

Pepperoni batter was prepared with fat contents of about 15, 20, and 32% (wt/wt) and inoculated with a pediococcal starter culture and ≥2.0 × 107 CFU/g of a five-strain inoculum of Escherichia coli O157:H7. The batter was fermented at 96°F (ca. 36°C) and 85% relative humidity (RH) to pH ≤ 4.8 and then dried at 55°F (ca. 13°C) and 65% RH to a moisture/protein ratio of ≤1.6:1. For storage, slices were packaged under air or vacuum and stored at 39°F (ca. 4°C) and 70°F (ca. 21°C). For baking, frozen slices were placed on retail frozen cheese pizzas that were subsequently baked at 275°F (ca. 135°C), 375°F (ca. 191°C), or 475°F (ca. 246°C) for 0 to 20 min. Appreciable differences related to fat levels were observed after drying; pathogen numbers decreased by 1.04, 1.31 and 1.62 log10 units in sticks prepared from batter at initial fat levels of 15, 20, and 32%, respectively. During storage, the temperature rather than the atmosphere had the greater effect on pathogen numbers, with similar viability observed among the three fat levels tested. At 70°F (ca. 21°C), compared to original levels, pathogen numbers decreased by ≥5.56 and ≥4.53 log10 units within 14 days in slices stored under air and vacuum, respectively, whereas at 39°F (ca. 4°C) numbers decreased by ≤2.43 log10 CFU/g after 60 days of storage under either atmosphere. Baking, as expected, resulted in greater reductions in pathogen numbers as the temperature and/or time of baking increased. However, it was still possible to recover the pathogen by enrichment after baking frozen slices on frozen pizza at 475°F (ca. 246°C) for 10 min or at 375°F (ca. 191°C) for 15 min. The calculated D values for all three temperatures tested increased as the fat content of the batter increased from 15 to 20 to 32%. The present study confirmed that fermentation and drying were sufficient to reduce levels of E. coli O157:H7 in pepperoni sticks by <2.0 log10 CFU/g. Storage of slices for at least 14 days at ambient temperature under air resulted in a >5.5-log10-unit total reduction of the pathogen. Baking slices on frozen pizza for at least 15 min at 475°F (ca. 246°C) or 20 min at 375°F (ca. 191°C) was necessary to reduce pathogen numbers to below detection by both direct plating and enrichment.

Growth and Death of Selected Microorganisms in Ultrafiltered Milk

1986 ◽  
Vol 49 (3) ◽  
pp. 233-235 ◽  
Author(s):  
PATRICIA HAGGERTY ◽  
NORMAN N. POTTER
Keyword(s):  
Escherichia Coli ◽  
Staphylococcus Aureus ◽  
Skim Milk ◽  
Laboratory Scale ◽  
The Other ◽  
Streptococcus Faecalis ◽  
E Coli ◽  
Milk Samples ◽  
D Values ◽  
D Value

Studies were made to compare the growth and death of Staphylococcus aureus, Streptococcus faecalis and Escherichia coli in skim milk concentrated by ultrafiltration to that in unconcentrated skim milk. Skim milk was volume concentrated to 2× in laboratory-scale stirred UF cells. Behavior of the organisms was analyzed in four inoculated milk samples: 2× retentate, 1× water-diluted retentate, milk equivalent (retentate plus permeate) and unconcentrated skim milk. Growth of each organism and of total aerobes did not vary in the four milk samples at either 7 or 13°C. For S. faecalis and E. coli, D-values for samples heated to 62.7°C did not significantly differ in the four milk samples (p>0.01). The D-value of S. aureus in water-diluted retentate was slightly but significantly lower than those in the other three milk samples (p<0.01), possibly due to the lowered lactose level in this sample.

Fate of Escherichia coli O157:H7 during Composting of Bovine Manure in a Laboratory-Scale Bioreactor

2003 ◽  
Vol 66 (1) ◽  
pp. 25-30 ◽  
Author(s):  
XIUPING JIANG ◽  
JENNIE MORGAN ◽  
MICHAEL P. DOYLE
Keyword(s):  
Escherichia Coli ◽  
Moisture Content ◽  
Enrichment Culture ◽  
Escherichia Coli O157 ◽  
External Temperature ◽  
E Coli ◽  
Self Heating ◽  
Large Populations ◽  
Constant Moisture Content ◽  
Carbon Nitrogen Ratio

Inactivation profiles of Escherichia coli O157:H7 in inoculated bovine manure–based compost ingredients were determined by composting these ingredients in a bioreactor under controlled conditions. A 15-liter bioreactor was constructed to determine the fate of E. coli O157:H7 and changes in pH, moisture content, temperature, and aerobic mesophilic and thermophilic bacterial counts during composting. Fresh cow manure, wheat straw, cottonseed meal, and ammonium sulfate were combined to obtain a moisture content of ca. 60% and a carbon/nitrogen ratio of 29:1. The compost ingredients were held in the bioreactor at a constant external temperature of 21 or 50°C. Self-heating of the ingredients due to microbial activity occurred during composting, with stratified temperatures occurring within the bioreactor. At an external temperature of 21°C, self-heating occurred for 0 to 3 days, depending on the location within the bioreactor. E. coli O157:H7 populations increased by 1 to 2 log10 CFU/g during the initial 24 h of composting and decreased by ca. 3.5 log10 CFU/g near the bottom of the bioreactor and by ca. 2 log10 CFU/g near the middle and at the top during 36 days of composting. At an external temperature of 50°C, E. coli O157:H7 was inactivated rapidly (by ca. 4.9 log10 CFU/g at the top of the bioreactor, by 4.0 log10 CFU/g near the middle, and by 5.9 log10 CFU/g near the bottom) within 24 h of composting. When inoculated at an initial level of ca. 107 CFU/g, E. coli O157:H7 survived for 7 days but not for 14 days at all three sampling locations, as indicated by either direct plating or enrichment culture. At the top of the bioreactor a relatively constant moisture content of 60% was maintained, whereas the moisture content near the bottom decreased steadily to 37 to 45% over 14 days of composting. The pH of the composting mixture decreased to ca. 6 within 1 to 3 days and subsequently increased to 8 to 9. Results obtained in this study indicate that large populations (104 to 107 CFU/g) of E. coli O157:H7 survived for 36 days during composting in a bioreactor at an external temperature of 21°C but were inactivated to undetectable levels after 7 to 14 days when the external temperature of the bioreactor was 50°C. Hence, manure contaminated with large populations (e.g., 107 CFU/g) of E. coli O157:H7 should be composted for more than 1 week, and preferably for 2 weeks, when held at a minimum temperature of 50°C.

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.

Factors Impacting the Regrowth of Escherichia coli O157:H7 in Dairy Manure Compost

2009 ◽  
Vol 72 (7) ◽  
pp. 1576-1584 ◽  
Author(s):  
JINKYUNG KIM ◽  
FENG LUO ◽  
XIUPING JIANG
Keyword(s):  
Escherichia Coli ◽  
Moisture Content ◽  
Room Temperature ◽  
Dairy Manure ◽  
Population Increase ◽  
Escherichia Coli O157 ◽  
Inoculum Level ◽  
Factors Affecting ◽  
E Coli ◽  
Manure Compost

The environmental variables affecting Escherichia coli O157:H7 regrowth in dairy manure compost were investigated. Factors evaluated were moisture content, strain variation, growth medium of inoculum, level of background microflora and inoculum, different days of composting, and acclimation at room temperature. A mathematical model was applied to describe E. coli O157 regrowth potential in compost. Repopulation occurred in autoclaved compost with a moisture content as low as 20% (water activity of 0.986) in the presence of background microflora of 2.3 to 3.9 log CFU/g. The population of all three E. coli O157 strains increased from ca. 1 to 4.85 log CFU/g in autoclaved compost, with the highest increase in the spinach-outbreak strain. However, E. coli O157 regrowth was suppressed by background microflora at ca. 6.5 log CFU/g. By eliminating acclimation at room temperature and increasing the inoculum level to ca. 3 log CFU/g, E. coli O157:H7 could regrow in the presence of high levels of background microflora. E. coli O157:H7 regrowth in the autoclaved compost collected from the field study was evident at all sampling days, with the population increase ranging from 3.49 to 6.54 log CFU/g. The fate of E. coli O157:H7 in compost was well described by a Whiting and Cygnarowicz-Provost model, with R2 greater than 0.9. The level of background microflora was a significant factor for both growth and death parameters. Our results reveal that a small number of E. coli O157 cells can regrow in compost, and both background microflora and moisture content were major factors affecting E. coli O157:H7 growth.

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