Ascorbic Acid Enhances Destruction of Escherichia coli O157:H7 during Home-Type Drying of Apple Slices

2001 ◽  
Vol 64 (8) ◽  
pp. 1244-1248 ◽  
Author(s):  
JENNIFER A. BURNHAM ◽  
PATRICIA A. KENDALL ◽  
JOHN N. SOFOS
Keyword(s):  
Escherichia Coli ◽  
Ascorbic Acid ◽  
Acid Solution ◽  
Escherichia Coli O157 ◽  
Bacterial Populations ◽  
Ascorbic Acid Solution ◽  
Initial Inoculum ◽  
E Coli ◽  
Apple Slices ◽  
Agar Media

Destruction of Escherichia coli O157:H7 was evaluated on inoculated apple slices dehydrated at two temperatures with and without application of predrying treatments. Half-ring slices (0.6 cm thick) of peeled and cored Gala apples were inoculated by immersion for 30 min in a four-strain composite inoculum of E. coli O157:H7. The inoculated slices (8.7 to 9.4 log CFU/g) either received no predrying treatment (control), were soaked for 15 min in a 3.4% ascorbic acid solution, or were steam blanched for 3 min at 88°C immediately prior to drying at 57.2 or 62.8°C for up to 6 h. Samples were plated on tryptic soy (TSA) and sorbitol MacConkey (SMAC) agar media for direct enumeration of surviving bacterial populations. Steam blanching changed initial inoculation levels by +0.3 to −0.7 log CFU/g, while immersion in the ascorbic acid solution reduced the inoculation levels by 1.4 to 1.6 log CFU/g. Dehydration of control samples for 6 h reduced mean bacterial populations by 2.9 log CFU/g (TSA or SMAC) at 57.2°C and by 3.3 (SMAC) and 3.5 (TSA) log CFU/g at 62.8°C. Mean decreases from initial inoculum levels for steam-blanched slices after 6 h of drying were 2.1 (SMAC) and 2.0 (TSA) log CFU/g at 57.2°C, and 3.6 (TSA or SMAC) log CFU/g at 62.8°C. In contrast, initial bacterial populations on ascorbic acid–pretreated apple slices declined by 5.0 (SMAC) and 5.1 (TSA) log CFU/g after 3 h of dehydration at 57.2°C, and by 7.3 (SMAC) and 6.9 (TSA) log CFU/g after 3 h at 62.8°C. Reductions on slices treated with ascorbic acid were in the range of 8.0 to 8.3 log CFU/g after 6 h of drying, irrespective of drying temperature or agar medium used. The results of immersing apple slices in a 3.4% ascorbic acid solution for 15 min prior to drying indicate that a predrying treatment enhances the destruction of E. coli O157:H7 on home-dried apple products.

Comparison of Methods for Detection and Isolation of Cold- and Freeze-Stressed Escherichia coli O157:H7 in Raw Ground Beef†

2007 ◽  
Vol 70 (7) ◽  
pp. 1663-1669 ◽  
Author(s):  
PINA M. FRATAMICO ◽  
LORI K. BAGI
Keyword(s):  
Escherichia Coli ◽  
Ground Beef ◽  
Escherichia Coli O157 ◽  
Pcr Assay ◽  
Initial Inoculum ◽  
E Coli ◽  
Multiplex Pcr Assay ◽  
Treatment Type ◽  
Agar Media ◽  
Main Effects

A comparison was made of the relative efficiencies of three enrichment media, RapidChek Escherichia coli O157:H7 enrichment broth (REB), R&F broth (RFB), and modified E. coli broth containing novobiocin (mEC+n), and four selective plating media for detection of cold- and freeze-stressed E. coli O157:H7 in raw ground beef. Ground beef (25 g) was inoculated with E. coli O157:H7 at ≤0.5 and ≤2 CFU/g, and samples were then enriched immediately or were stored at 4°C for 72 h or at −20°C for 2 weeks and then enriched. After 8 or 20 h of enrichment, the cultures were plated onto R&F E. coli O157: H7 chromogenic plating medium, cefixime-tellurite sorbitol MacConkey agar, CHROMagar O157, and Rainbow agar O157 and tested using the RapidChek E. coli O157 lateral flow immunoassay and a multiplex PCR assay targeting the E. coli O157: H7 eae, stx1, and stx2 genes. Recovery of E. coli O157:H7 on the four agar media was 4.0 to 7.9 log CFU/ml with the REB enrichment, 1.4 to 7.4 log CFU/ml with RFB, 1.7 to 6.7 log CFU/ml with mEC+n incubated at 42°C, and 1.3 to 3.3 log CFU/ml from mEC+n incubated at 35°C. The percentages of positive ground beef samples containing nonstressed, cold-stressed, and freeze-stressed E. coli O157:H7 as obtained by plating, the immunoassay, and the PCR assay were 97, 88, and 97%, respectively, with REB, 92, 81, and 78%, respectively, with RFB, 97, 58, and 53%, respectively, with mEC+n incubated at 42°C, and 22, 31, and 25%, respectively, with mEC+n incubated at 35°C. Logistic regression analyses of the data indicated significant main effects of treatment, type of medium, enrichment time, inoculum concentration, and detection method. In particular, a positive result was 1.1 times more likely to occur after 20 h of enrichment than after 8 h, 25 times more likely with RFB and REB than with mEC+nat35°C, 3.7 times more likely with an initial inoculum of ≤2.0 CFU/g than with ≤0.5 CFU/g, 2.5 to 3 times more likely using freeze-stressed or nonstressed bacteria than with cold-stressed bacteria, and 2.5 times more likely by plating than by the immunoassay or the PCR assay. REB had better overall performance for enrichment of cold- and freeze-stressed E. coli O157:H7 present in ground beef than did the other media examined.

Inhibition of Listeria monocytogenes and Escherichia coli O157:H7 on Beef by Application of Organic Acids†

1996 ◽  
Vol 59 (4) ◽  
pp. 370-373 ◽  
Author(s):  
R. K. PODOLAK ◽  
J. F. ZAYAS ◽  
C. L. KASTNER ◽  
D. Y. C. FUNG
Keyword(s):  
Escherichia Coli ◽  
Listeria Monocytogenes ◽  
Fumaric Acid ◽  
Rank Order ◽  
Escherichia Coli O157 ◽  
Inoculum Level ◽  
Initial Inoculum ◽  
E Coli ◽  
Lean Beef ◽  
Lactic Acids

Lean beef surfaces were inoculated with Escherichia coli O157:H7 and Listeria monocytogenes and then sanitized with fumaric, acetic, or lactic acid alone and in combined solutions of those acids at 55°C for 5 s. The initial inoculum level was 8.62 log CFU/cm2 and 5.13 log CFU/cm2 for L. monocytogenes and E. coli O157:H7, respectively. Fumaric acid at a concentration of 1% was the most effective acid in reducing the populations of L. monocytogenes by up to 1 log unit and E. coli O157:H7 by up to 1.3 log units when compared with acetic or lactic acids. The rank order of acids tested against the growth of L. monocytogenes and E. coli O157:H7 was fumaric acid followed by lactic and acetic acids. Fumaric acid at concentrations of 1.0% and 1.5% was more effective than any of the combined solutions of acids.

Survival of Escherichia coli O157:H7, Salmonella Enteritidis, Staphylococcus aureus, and Listeria monocytogenes in Kimchi

2004 ◽  
Vol 67 (7) ◽  
pp. 1497-1500 ◽  
Author(s):  
Y. INATSU ◽  
M. L. BARI ◽  
S. KAWASAKI ◽  
K. ISSHIKI
Keyword(s):  
Escherichia Coli ◽  
Staphylococcus Aureus ◽  
Listeria Monocytogenes ◽  
Incubation Period ◽  
Salmonella Enteritidis ◽  
Detectable Level ◽  
Escherichia Coli O157 ◽  
Inoculum Level ◽  
Initial Inoculum ◽  
E Coli

The survival of gram-positive and gram-negative foodborne pathogens in both commercial and laboratory-prepared kimchi (a traditional fermented food widely consumed in Japan) was investigated. It was found that Escherichia coli O157:H7, Salmonella Enteritidis, Staphylococcus aureus, and Listeria monocytogenes could survive in both commercial and laboratory-prepared kimchi inoculated with these pathogens and incubated at 10°C for 7 days. However, when incubation was prolonged, the S. aureus level decreased rapidly from the initial inoculum level to the minimum detectable level within 12 days, whereas Salmonella Enteritidis and L. monocytogenes took 16 days to reach similar levels in commercial kimchi. On the other hand, E. coli O157:H7 remained at high levels throughout the incubation period. For laboratory-prepared kimchi, the S. aureus level decreased rapidly from the initial inoculum level to the minimum detectable level within 12 days, and L. monocytogenes took 20 days to reach a similar level. E. coli O157:H7 and Salmonella Enteritidis remained at high levels throughout the incubation period. The results of this study suggest that the contamination of kimchi with E. coli O157:H7, Salmonella Enteritidis, S. aureus, or L. monocytogenes at any stage of production or marketing could pose a potential risk.

Effects of Oxidative Compounds on Thermotolerance in Escherichia coli O157:H7 Strains EO139 and 380-94

2005 ◽  
Vol 68 (11) ◽  
pp. 2443-2446 ◽  
Author(s):  
ISABEL C. BLACKMAN ◽  
YOUNG W. PARK ◽  
MARK A. HARRISON
Keyword(s):  
Oxidative Stress ◽  
Escherichia Coli ◽  
Ascorbic Acid ◽  
Lethal Effect ◽  
Iron Chloride ◽  
Plate Count ◽  
Escherichia Coli O157 ◽  
Bacterial Cells ◽  
E Coli ◽  
Chloride Hexahydrate

An oxidative complex composed of ferric iron chloride hexahydrate, ADP, and ascorbic acid can generate hydrogen peroxide and hydroxyl radicals in fibroblasts. These compounds are naturally found in meat and meat-based products and may elicit oxidative stress on Escherichia coli O157:H7, thus conferring thermotolerance to the bacterium due to the phenomenon of the global stress response. The effect of the levels of the oxidative complex on the thermotolerance of E. coli O157:H7 was investigated. Cultures of E. coli O157:H7 strains EO139 and 380-94 were mixed in three different concentrations (10:10: 40, 15:15:60, and 20:20:80 μM) of the oxidative complex (iron III chloride, ADP, and ascorbic acid, respectively). The samples were inserted into capillary tubes and heated in a circulating water bath at 59 and 60°C for EO139 and 380-94, respectively. Tubes were removed at intervals of 5 min for up to 1 h and contents spirally plated on plate count agar that was incubated for 48 h at 37°C. The thermotolerance of both E. coli O157:H7 strains EO139 and 380-94 was influenced by the concentrations of the oxidative complex. The ratio of 10:10:40 μM enhanced thermotolerance of EO139 and 390-94 at 59 and 60°C, respectively. However, exposure to the ratios of 15:15:60 and 20:20:80 μM rendered the pathogen more sensitive to the lethal effect and did not enhance the thermotolerance of the cells. The significance of this study is twofold. This experiment proves that oxidative stress can enhance thermotolerance of bacterial cells induced by an oxidative complex if only in a specific ratio and concentration. It is possible to speculate that if the chemical compounds are present in this ratio in meats, they may enhance the thermal resistance of E. coli O157:H7 and make the bacteria more difficult to eliminate, thus increasing the risk of foodborne illness in consumers.

scholarly journals Evaluation of stx1, stx2, hlyA, and eaeA Virulence Genes in Escherichia coli O157:H7 Isolated from Meat (Beef and Mutton) in Hamedan, Iran, During 2015-2016

2020 ◽  
Vol 8 (2) ◽  
pp. 55-59
Author(s):  
Fatemeh Binandeh ◽  
Mohammadreza Pajohi-Alamoti ◽  
Pezhman Mahmoodi ◽  
Azam Ahangari
Keyword(s):  
Escherichia Coli ◽  
Virulence Genes ◽  
Escherichia Coli O157 ◽  
Isolation And Identification ◽  
E Coli ◽  
Multiplex Pcr Assay ◽  
Agar Media ◽  
Cattle Meat ◽  
Meat Samples ◽  
Encoding Genes

Background and Objectives: Consuming raw or undercooked cattle meat is the most common transmission way of infection with Escherichia coli O157:H7. The present study aimed to identify virulence genes stx1, stx2, hlyA, and eaeA in E. coli isolated from meat samples (beef and mutton) in Hamedan during 2015 and 2016. Materials and Methods: For this purpose, the swabs were randomly taken from 160 meat samples including 80 beef samples and 80 mutton samples from butcher shops. Isolation and identification of E. coli cells were conducted by culturing the swab samples on MacConkey agar and Eosin methylene blue agar media. Then, the identity of the suspected E. coli O157:H7 colonies was investigated by a multiplex PCR assay and eventually, the isolates were evaluated for the presence of stx1, stx2, hlyA, eaeA virulence genes. Results: The results showed that out of 160 cultured samples on the selective media, 60 samples (37.5%) were contaminated with E. coli. O157:H7, O157, and H7 strains were identified using PCR, among which only E. coli O157:H7 possessed all four virulence factor encoding genes. Conclusion: The results of this study showed that beef could be a reservoir for E. coli O157:H7, and it may be involved in the transmission of this pathogen to humans.

Death of Salmonella, Escherichia coli O157:H7, and Listeria monocytogenes in Shelf-Stable, Dairy-Based, Pourable Salad Dressings

2006 ◽  
Vol 69 (4) ◽  
pp. 801-814 ◽  
Author(s):  
LARRY R. BEUCHAT ◽  
JEE-HOON RYU ◽  
BARBARA B. ADLER ◽  
M. DAVID HARRISON
Keyword(s):  
Escherichia Coli ◽  
Listeria Monocytogenes ◽  
Storage Period ◽  
Escherichia Coli O157 ◽  
Blue Cheese ◽  
Initial Inoculum ◽  
E Coli ◽  
Reduced Fat ◽  
Yeasts And Molds ◽  
Shelf Stable

The objectives of this study were to determine the death rates of Salmonella, Escherichia coli O157:H7, and Listeria monocytogenes in three commercially manufactured full-fat ranch salad dressings, three reduced-fat ranch salad dressings, two full-fat blue cheese salad dressings, and two reduced-fat blue cheese salad dressings and to affirm the expectation that these dressings do not support the growth of these pathogens. The respective initial pH values of the four types of shelf-stable, dairy-based, pourable dressings were 2.87 to 3.72, 2.82 to 3.19, 3.08 to 3.87, and 2.83 to 3.49, respectively. Dressings were inoculated with low (2.4 to 2.5 log CFU/g) and high (5.3 to 5.9 log CFU/g) populations of separate five-strain mixtures of each pathogen and stored at 25°C for up to 15 days. Regardless of the initial inoculum population, all test pathogens rapidly died in all salad dressings. Salmonella was undetectable by enrichment (<1 CFU/25-ml sample in three replicate trials) in all salad dressings within 1 day, and E. coli O157:H7 and L. monocytogenes were reduced to undetectable levels by enrichment between 1 and 8 days and 2 and 8 days, respectively. E. coli O157:H7 was not detected in 4 of the 10 salad dressings stored for 2 or more days and 9 of the 10 dressings stored for 6 or more days after inoculation. L. monocytogenes was detected in 9 of the 10 salad dressings stored for 3 days but in only one dressing, by enrichment, at 6 days, indicating that it had the highest tolerance among the three pathogens to the acidic environment imposed by the dressings. Overall, the type of dressing (i.e., ranch versus blue cheese) and level of fat in the dressings did not have a marked effect on the rate of inactivation of pathogens. Total counts and populations of lactic acid bacteria and yeasts and molds remained low or undetectable (<1.0 log CFU/ml) throughout the 15-day storage period. Based on these observations, shelf-stable, dairy-based, pourable ranch and blue cheese salad dressings manufactured by three companies and stored at 25°C do not support the growth of Salmonella, E. coli O157:H7, and L. monocytogenes and should not be considered as potentially hazardous foods (time-temperature control for safety foods) as defined by the U.S. Food and Drug Administration Food Code.

Parameters Affecting the Efficacy of Spray Washes against Escherichia coli O157:H7 and Fecal Contamination on Beef†

1997 ◽  
Vol 60 (6) ◽  
pp. 614-618 ◽  
Author(s):  
CATHERINE N. CUTTER ◽  
WARREN J. DORSA ◽  
GREGORY R. SIRAGUSA
Keyword(s):  
Escherichia Coli ◽  
Acetic Acid ◽  
Tap Water ◽  
Physiological Saline ◽  
Tissue Type ◽  
Escherichia Coli O157 ◽  
Bacterial Populations ◽  
E Coli ◽  
Bovine Feces ◽  
Beef Carcass

A series of progressive experiments was conducted with a model carcass washer using tap water and 2% acetic acid sprays to determine if tissue type, inoculation menstruum, bacterial level, or spray temperature affect removal of bacteria from beef carcass tissue during spray washing. For the first experiment, prerigor (15 min postexsanguination), postrigor (24 h postexsanguination), or postrigor frozen (−20°C, 7 days), thawed, lean beef carcass tissue (BCT) was inoculated with bovine feces and subjected to spray washing (15 s, 56°C) with water or acetic acid. Spray washing with either compound resulted in bacterial populations that were similar for prerigor and postrigor BCT; however, remaining bacterial populations from spray-treated postrigor, frozen BCT were significantly (P ≤ 0.05) less than for the other two tissue types. For the second experiment, prerigor, lean BCT was inoculated with Escherichia coli O157:H7 suspended in bovine feces or physiological saline and spray washed (15 s, 56°C) with water or acetic acid. Bacterial populations were reduced to similar levels with acid sprays, regardless of menstruum. For the third experiment, E. coli O157:H7 in feces was used to contaminate prerigor lean BCT to obtain different initial bacterial levels (7, 5,3, and 1 log CFU/cm2). Spray washes (15 s, 56°C) with acetic acid reduced the level of the pathogen to 2.51 and 0.30 log CFU/cm2 when initial bacterial levels were 7 and 5 log CFU/cm2, and to undetectable levels when initial bacterial levels were 3 and 1 log CFU/cm2. In a fourth experiment, water or acetic acid (15 s), ranging from 30 to 70°C was applied to beef tissue contaminated with E. coli O157:H7 in feces. Remaining bacterial populations were not different between the water treatments or between the acid treatments at any temperature. While variables such as bacterial level and inoculation menstruum may affect the efficacy of spray washing with organic acids, these results indicate that tissue type or spray temperature do not.

High-Pressure Resistance Variation of Escherichia coli O157:H7 Strains and Salmonella Serovars in Tryptic Soy Broth, Distilled Water, and Fruit Juice

2007 ◽  
Vol 70 (9) ◽  
pp. 2078-2083 ◽  
Author(s):  
BROOKE M. WHITNEY ◽  
ROBERT C. WILLIAMS ◽  
JOSEPH EIFERT ◽  
JOSEPH MARCY
Keyword(s):  
Escherichia Coli ◽  
High Pressure ◽  
Orange Juice ◽  
High Pressure Processing ◽  
Distilled Water ◽  
Escherichia Coli O157 ◽  
Bacterial Populations ◽  
E Coli ◽  
Log Reduction ◽  
Salmonella Serovars

The effect of high pressure on the log reduction of six strains of Escherichia coli O157:H7 and five serovars of Salmonella enterica was investigated in tryptic soy broth, sterile distilled water, and commercially sterile orange juice (for Salmonella) and apple cider (for E. coli). Samples were subjected to high-pressure processing treatment at 300 and 550 MPa for 2 min at 6°C. Samples were plated onto tryptic soy agar directly after pressurization and after being held for 24 h at 4°C. At 300 MPa, little effect was seen on E. coli O157:H7 strains, while Salmonella serovars varied in resistance, showing reductions between 0.26 and 3.95 log CFU/ml. At 550 MPa, E. coli O157:H7 strains exhibited a range of reductions (0.28 to 4.39 log CFU/ml), while most Salmonella populations decreased beyond the detection limit (>5-log CFU/ml reduction). The most resistant strains tested were E. coli E009 and Salmonella Agona. Generally, bacterial populations in fruit juices showed larger decreases than did populations in tryptic soy broth and distilled water. E. coli O157:H7 cultures held for 24 h at 4°C after treatment at 550 MPa showed a significant log decrease as compared with cultures directly after treatment (P ≤ 0.05), while Salmonella serovars did not show this significant decrease (P > 0.05). All Salmonella serovars tested in orange juice treated at 550 MPa for 2 min at 6°C and held for 24 h showed a >5-log decrease, while E. coli O157:H7 strains require a higher pressure, higher temperature, longer pressurization, or a chemical additive to achieve a 5-log decrease.

Survival of Enterohemorrhagic Escherichia coli O157:H7 in Bovine Feces Applied to Lettuce and the Effectiveness of Chlorinated Water as a Disinfectant

1999 ◽  
Vol 62 (8) ◽  
pp. 845-849 ◽  
Author(s):  
LARRY R. BEUCHAT
Keyword(s):  
Escherichia Coli ◽  
Enterohemorrhagic Escherichia Coli ◽  
Escherichia Coli O157 ◽  
Initial Inoculum ◽  
E Coli ◽  
Iceberg Lettuce ◽  
Viable Cells ◽  
Peptone Water ◽  
Four Levels ◽  
Bovine Feces

Bovine feces are a potential vehicle for transmitting enterohemorrhagic Escherichia coli O157:H7 to humans. A study was undertaken to determine survival characteristics of E. coli O157:H7 on iceberg lettuce using 0.1% peptone water and bovine feces as carriers for inocula. Four levels of inoculum, ranging from 100 to 105 CFU of E. coli O157:H7 per g of lettuce, were applied. Populations surviving on lettuce stored at 4°C were monitored for up to 15 days. Regardless of the type of carrier, viable cells of E. coli O157:H7 were detected on lettuce after 15 days, even when the initial inoculum was 100 to 101 CFU/g. Spray treatments of lettuce with 200 ppm chlorine solution or deionized water were equally effective in killing or removing E. coli O157:H7 from lettuce. Holding lettuce for 5 min after spray treatment was not more effective in reducing populations than holding for 1 min before rinsing with water. Prevention of contamination of lettuce with bovine feces that may harbor E. coli O157:H7 as well as other infectious microorganisms is essential to minimizing the risk of illness. The development of sanitizers more efficacious than chlorine for the removal of pathogens from raw fruits and vegetable is needed.

Effects of Steam-Vacuuming and Hot Water Spray Wash on the Microflora of Refrigerated Beef Carcass Surface Tissue Inoculated with Escherichia coli O157:H7, Listeria innocua, and Clostridium sporogenes†

1997 ◽  
Vol 60 (2) ◽  
pp. 114-119 ◽  
Author(s):  
WARREN J. DORSA ◽  
CATHERINE N. CUTTER ◽  
GREGORY R. SIRAGUSA
Keyword(s):  
Escherichia Coli ◽  
Hot Water ◽  
Listeria Innocua ◽  
Escherichia Coli O157 ◽  
Clostridium Sporogenes ◽  
Bacterial Populations ◽  
Antibiotic Resistant ◽  
E Coli ◽  
Resistant Strains ◽  
Beef Carcass

The fates of several bacterial populations on beef carcass surfaces were examined immediately following hot water washes (W) delivered through a beef carcass wash cabinet or application of steam-vacuum (SV). Additionally, the long-range effectiveness of W and SV on several bacterial populations was also determined during storage up to 21 days at 5°C under vacuum-packaged conditions. Fresh, unaltered bovine feces spiked with antibiotic-resistant strains of Escherichia coli O157:H7, Listeria innocua, and Clostridium sporogenes were used to inoculate beef carcass tissue prior to W or SV treatment. All treatments were equally effective as is indicated by bacterial populations immediately following any of the treatments (P > 0.05); however, the combination of SV followed by W consistently produced arithmetically greater bacterial reductions. In general, all treatments produced initial reductions of up to 2.7 log CFU/cm2 for APC, lactic acid bacteria, and L. innocua, but by 14 days bacterial numbers had increased to levels of at least 7 log CFU/cm2. E. coli O157:H7 was initially reduced by as much as 3.4 log CFU/cm2 and did not grow to original inoculation levels for the duration of the experiment. Vegetative counts of C. sporogenes were initially reduced by as much as 3.4 log CFU/cm2, and numbers continued to decline for the duration of the study. These results indicate that the use of W and SV effectively reduces bacterial populations from beef carcass tissue immediately after treatment. Additionally, storage of treated tissue up to 21 days at 5°C did not appear to offer any competitive advantage to potentially pathogenic microorganisms.

Sign in / Sign up

Export Citation Format

Share Document