Survival and Growth of Escherichia coli O157:H7 in Roast Beef and Salami after Exposure to an Alkaline Cleaner

2004 ◽  
Vol 67 (10) ◽  
pp. 2107-2116 ◽  
Author(s):  
MANAN SHARMA ◽  
GLENNER M. RICHARDS ◽  
LARRY R. BEUCHAT
Keyword(s):  
Escherichia Coli ◽  
Storage Period ◽  
Escherichia Coli O157 ◽  
Mold Growth ◽  
Wild Type ◽  
Macconkey Agar ◽  
E Coli ◽  
Different Temperatures ◽  
Survival And Growth ◽  
Roast Beef

Survival and growth of wild-type (EDL 933) and rpoS-deficient (FRIK 816-3) strains of Escherichia coli O157:H7 after exposure to an alkaline cleaner for 2 min and inoculating into roast beef (pH 6.3) and hard salami (pH 4.9) at low (0.003 to 0.52 CFU/g) and high (0.69 to 31.5 CFU/g) populations were determined. Roast beef was stored at 4 and 12°C; salami was stored at 4, 12, and 20°C. At 4°C, untreated cells of both strains showed greater reductions in populations in salami than in roast beef during a 21-day storage period. Populations of treated and untreated cells recovered from roast beef and salami stored at 4°C on tryptic soy agar were significantly (P ≤ 0.05) higher than on sorbitol MacConkey agar, indicating that a portion of the cells was injured. Treated and untreated cells grew in roast beef at 12°C. Growth of treated cells of the FRIK 816-3 strain in roast beef at 12°C was significantly slower than that of the EDL 933 strain. Populations of both strains decreased at different rates in salami stored at different temperatures (20°C > 12°C > 4°C). E. coli O157:H7 strain EDL 933 grew more rapidly at 20°C in a slurry (pH 5.97) prepared from stored salami (17 days at 20°C) on which Penicillium chrysogenum had grown than in a slurry (5.23) prepared from salami showing no mold growth. Within 2 to 3 days, populations were ca. 3 log CFU/ml higher in slurry made from infected salami than in control salami. Results indicate that treatment of E. coli O157: H7 with an alkaline cleaner for 2 min does not impair resuscitation and growth of surviving cells in roast beef at 12°C. Cross protection of cells exposed to an alkaline cleaner against subsequent stress conditions imposed by roast beef and salami stored at 4°C was not evident in either of the test strains.

Viability of Acid-Adapted Escherichia coli O157:H7 in Ground Beef Treated with Acidic Calcium Sulfate

2004 ◽  
Vol 67 (3) ◽  
pp. 591-595 ◽  
Author(s):  
LARRY R. BEUCHAT ◽  
ALAN J. SCOUTEN
Keyword(s):  
Escherichia Coli ◽  
Acetic Acid ◽  
Calcium Sulfate ◽  
Ground Beef ◽  
Storage Period ◽  
Acid Tolerance ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Acidic Environments ◽  
Subsequent Acid

The effects of lactic acid, acetic acid, and acidic calcium sulfate (ACS) on viability and subsequent acid tolerance of three strains of Escherichia coli O157:H7 were determined. Differences in tolerance to acidic environments were observed among strains, but the level of tolerance was not affected by the acidulant to which cells had been exposed. Cells of E. coli O157:H7 adapted to grow on tryptic soy agar acidified to pH 4.5 with ACS were compared to cells grown at pH 7.2 in the absence of ACS for their ability to survive after inoculation into ground beef treated with ACS, as well as untreated beef. The number of ACS-adapted cells recovered from ACS-treated beef was significantly (α = 0.05) higher than the number of control cells recovered from ACS-treated beef during the first 3 days of a 10-day storage period at 4°C, suggesting that ACS-adapted cells might be initially more tolerant than unadapted cells to reduced pH in ACS-treated beef. Regardless of treatment of ground beef with ACS or adaptation of E. coli O157:H7 to ACS before inoculating ground beef, the pathogen survived in high numbers.

Use of the Systems Approach To Determine the Fate of Escherichia coli O157:H7 on Fresh Lettuce and Spinach

2009 ◽  
Vol 72 (7) ◽  
pp. 1560-1568 ◽  
Author(s):  
HELGA J. DOERING ◽  
MARK A. HARRISON ◽  
RUTH A. MORROW ◽  
WILLIAM C. HURST ◽  
WILLIAM L. KERR
Keyword(s):  
Escherichia Coli ◽  
Systems Approach ◽  
Storage Temperature ◽  
Storage Period ◽  
Categorical Variables ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Field Temperature ◽  
Before And After ◽  
Handling Practices

Lettuce and spinach inoculated with Escherichia coli O157:H7 were processed and handled in ways that might occur in commercial situations, including variations in holding times before and after product cooling, transportation conditions and temperatures, wash treatments, and product storage temperatures and times. Populations of background microflora and E. coli O157:H7 were enumerated after each step in the system. Data analysis was done to predict response variables with a combination of independent categorical variables. Field temperature, time before cooling, and wash treatment significantly affected E. coli O157:H7 populations on both products. The lowest populations of E. coli O157:H7 were encountered when precool time was minimal, lettuce was washed with chlorine, and storage temperature was 4°C. For lettuce, field and transportation temperature were not important once the storage period started, whereas after 2 days E. coli O157:H7 populations on packaged baby spinach were not affected by field temperature. On chopped iceberg lettuce and whole leaf spinach that was packaged and stored at 4°C, E. coli O157:H7 contamination could still be detected after typical handling practices, although populations decreased from initial levels in many cases by at least 1.5 log units. In abusive cases, where populations increased, the product quality quickly deteriorated. Although E. coli O157:H7 levels decreased on products handled and stored under recommended conditions, survivors persisted. This study highlights practices that may or may not affect the populations of E. coli O157:H7 on the final product.

Fate of Escherichia coli O157:H7 in the Presence of Indigenous Microorganisms on Commercially Packaged Baby Spinach, as Impacted by Storage Temperature and Time†

2009 ◽  
Vol 72 (10) ◽  
pp. 2038-2045 ◽  
Author(s):  
YAGUANG LUO ◽  
QIANG HE ◽  
JAMES L. McEVOY ◽  
WILLIAM S. CONWAY
Keyword(s):  
Escherichia Coli ◽  
Product Quality ◽  
Elevated Temperatures ◽  
Storage Temperature ◽  
Escherichia Coli O157 ◽  
Indigenous Microorganisms ◽  
E Coli ◽  
Psychrotrophic Bacteria ◽  
Survival And Growth

This study investigated the effect of storage temperature and time on the survival and growth of Escherichia coli O157:H7, the growth of indigenous microorganisms, and the changes in product quality of packaged baby spinach. Commercial packages of spinach within 2 days of processing were cut open at one end, sprayed with fine mists of E. coli O157:H7 inoculum, resealed, and then stored at 1, 5, 8, and 12°C for 12 days until their labeled best-if-used-by dates. Microbial enumeration and product quality evaluation were conducted on day(s) 0, 3, 6, 9, and 12 postinoculation. Spinach held at 12°C supported significant (P < 0.001) E. coli O157:H7 growth, with a 1.0-log CFU/g increase within 3 days postinoculation, which was followed by additional growth during continued storage. E. coli O157:H7 grew slowly when held at 8°C, with a significant (P < 0.01) level of growth reached after 6 days of storage. However, on products held at 1 and 5°C, E. coli O157:H7 populations declined significantly (P < 0.01 and P < 0.001, respectively) within 3 days of storage. Aerobic mesophilic bacteria, psychrotrophic bacteria, and yeast and mold populations increased significantly at all storage temperatures, with more growth on products held at elevated temperatures. Product quality scores remained high within the first 6 days of storage, with a sharp decline noted on samples held at 12°C on day 9. Results suggest that E. coli O157:H7 can grow significantly on commercially packaged spinach held at 8°C or above before significant product quality deterioration occurs.

Attachment of Escherichia coli O157:H7 and Other Bacterial Cells Grown in Two Media to Beef Adipose and Muscle Tissues

1997 ◽  
Vol 60 (2) ◽  
pp. 102-106 ◽  
Author(s):  
LAURA CABEDO ◽  
JOHN N. SOFOS ◽  
GLENN R. SCHMIDT ◽  
GARY C. SMITH
Keyword(s):  
Escherichia Coli ◽  
Adipose Tissue ◽  
Muscle Tissue ◽  
Storage Period ◽  
Escherichia Coli O157 ◽  
Bacterial Cells ◽  
Liquid Droplets ◽  
E Coli ◽  
Attachment Strength ◽  
Beef Muscle

Three strains of Escherichia coli O157:H7 were grown in tryptic soy broth (TSB) or in a sterile cattle manure extract at 35°C for 18 ± 2 h. Aliquots from both inocula containing 106 CFU/ml were used to inoculate 1-cm3 cubes of beef muscle or adipose tissue by immersion for 20 min at 21°C. After removal from the inoculum, one-half of the samples were analyzed for bacterial cell numbers and pH, and the other half were stored at 4°C for 2 or 3 h before analysis. Samples were analyzed by enumerating bacteria present in liquid droplets deposited on the tissue and bacteria loosely or strongly attached to the tissue in order to determine attachment strength. Total numbers of cells on beef muscle tissue (bacteria in liquid droplets, as well as those loosely and strongly attached) were 5.65 ± 0.14 and 5.76 ± 0.26 log CFU/cm2 for E. coli O157:H7 inocula grown in TSB and manure extract, respectively. The differences in attachment strength between inocula from the two media were not significant (P > 0.05). A 2-h storage period after exposure of muscle tissue to an E. coli O157:H7 inoculum did not influence attachment strength. Numbers of bacteria attached to adipose tissue and muscle (5.31 ± 0.08 and 5.48 ± 0.09 log CFU/cm2, respectively) were not significantly different (P > 0.05). After 3 h at 4°C, the attachment strength of E. coli O157:H7 cells on muscle or adipose tissue had not changed. Overall, the culture medium and type of beef tissue did not affect the numbers of E. coli O157:H7 cells attached, nor the strength of their attachment, to muscle or adipose tissue.

scholarly journals Escherichia coli O157:H7 in Environments of Culture-Positive Cattle

2005 ◽  
Vol 71 (11) ◽  
pp. 6816-6822 ◽  
Author(s):  
Margaret A. Davis ◽  
Karen A. Cloud-Hansen ◽  
John Carpenter ◽  
Carolyn J. Hovde
Keyword(s):  
Escherichia Coli ◽  
Room Temperature ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Different Temperatures ◽  
Farm Structures ◽  
On Farm ◽  
Culture Positive ◽  
Culture Negative ◽  
Over Time

ABSTRACT Outbreaks of Escherichia coli O157:H7 disease associated with animal exhibits have been reported with increasing frequency. Transmission can occur through contact with contaminated haircoats, bedding, farm structures, or water. We investigated the distribution and survival of E. coli O157:H7 in the immediate environments of individually housed, experimentally inoculated cattle by systematically culturing feed, bedding, water, haircoat, and feed bunk walls for E. coli O157:H7 for 3 months. Cedar chip bedding was the most frequently culture-positive environmental sample tested (27/96 or 28.15%). Among these, 12 (44.0%) of positive bedding samples were collected when the penned animal was fecal culture negative. Survival of E. coli O157:H7 in experimentally inoculated cedar chip bedding and in grass hay feed was determined at different temperatures. Survival was longest in feed at room temperature (60 days), but bacterial counts decreased over time. The possibility that urine plays a role in the environmental survival of E. coli O157:H7 was investigated. Cedar chip bedding moistened with sterile water or bovine urine was inoculated with E. coli O157:H7. Bedding moistened with urine supported growth of E. coli O157:H7, whereas inoculated bedding moistened with only water yielded decreasing numbers of bacteria over time. The findings that environmental samples were frequently positive for E. coli O157:H7 at times when animals were culture negative and that urine provided a substrate for E. coli O157:H7 growth have implications for understanding the on-farm ecology of this pathogen and for the safety of ruminant animal exhibits, particularly petting zoos and farms where children may enter animal pens.

Survival and Growth of Listeria monocytogenes and Enterohemorrhagic Escherichia coli O157:H7 in Minimally Processed Artichokes

2003 ◽  
Vol 66 (12) ◽  
pp. 2203-2209 ◽  
Author(s):  
SUSANA SANZ ◽  
MERCEDES GIMÉNEZ ◽  
CARMEN OLARTE
Keyword(s):  
Escherichia Coli ◽  
Listeria Monocytogenes ◽  
Tap Water ◽  
Storage Period ◽  
Enterohemorrhagic Escherichia Coli ◽  
Fecal Coliforms ◽  
Escherichia Coli O157 ◽  
Natural Background ◽  
Minimally Processed ◽  
E Coli

The ability of Listeria monocytogenes and Escherichia coli O157:H7 inoculated by immersion (at 4.6 and 5.5 log CFU/g, respectively) to survive on artichokes during various stages of preparation was determined. Peeling, cutting, and disinfecting operations (immersion in 50 ppm of a free chlorine solution at 4°C for 5 min) reduced populations of L. monocytogenes and E. coli O157:H7 by only 1.6 and 0.8 log units, respectively. An organic acid rinse (0.02% citric acid and 0.2% ascorbic acid) was more effective than a tap water rinse in removing these pathogens. Given the possibility of both pathogens being present on artichokes at the packaging stage, their behavior during the storage of minimally processed artichokes was investigated. For this purpose, batches of artichokes inoculated with L. monocytogenes or E. coli O157:H7 (at 5.5 and 5.2 log CFU/g, respectively) were packaged in P-Plus film bags and stored at 4°C for 16 days. During this period, the equilibrium atmosphere composition and natural background microflora (mesophiles, psychrotrophs, anaerobes, and fecal coliforms) were also analyzed. For the two studied pathogens, the inoculum did not have any effect on the final atmospheric composition (10% O2, 13% CO2) or on the survival of the natural background microflora of the artichokes. L. monocytogenes was able to survive during the entire storage period in the inoculated batches, while the E. coli O157:H7 level increased by 1.5 log units in the inoculated batch during the storage period. The modified atmosphere was unable to control the behavior of either pathogen.

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.

Fate of Escherichia coli O157:H7 in Ground Apples Used in Cider Production

1998 ◽  
Vol 61 (10) ◽  
pp. 1372-1374 ◽  
Author(s):  
TOMEKA L. FISHER ◽  
DAVID A. GOLDEN
Keyword(s):  
Escherichia Coli ◽  
Statistical Difference ◽  
The Other ◽  
Escherichia Coli O157 ◽  
Apple Cultivar ◽  
Mold Growth ◽  
E Coli ◽  
Significant Difference ◽  
Golden Delicious ◽  
Pathogen Populations

Survival of Escherichia coli O157:H7 in ground Golden Delicious, Red Delicious, Rome, and Winesap apples stored at 4, 10, and 25°C was determined. E. coli O157:H7 populations were monitored for up to 18 days (4°C), 12 days (10°C), and 5 days (25°C), when mold contamination became visible. At 25°C, Red Delicious apples supported survival of E. coli O157:H7 better (P < 0.05) than the other cultivars, followed by Golden Delicious and Rome apples, which were not statistically different (P > 0.05). Winesap apples were the least favorable (P < 0.05) for survival of E. coli O157:H7 at 25°C. E. coli O157:H7 was recovered at similar rates from Golden Delicious and Red Delicious apples, (P > 0.05), but pathogen populations increased in both cultivars (P < 0.05) during storage at 25°C. At 10°C, survival of E. coli O157:H7 was poorest (P < 0.05) in ground Red Delicious apples, while there was no significant difference in survival of E. coli O157:H7 among ground Golden Delicious, Rome, or Winesap cultivars (P > 0.05). When stored at 4°C, Golden Delicious and Rome apples were not statistically different in supporting survival of the pathogen (P > 0.05) and there was no statistical difference in the recovery of E. coli O157:H7 from ground Red Delicious, Rome, and Winesap apples (P > 0.05). In general, apple pH increased during storage and was associated with mold growth. Results of this investigation indicate that there is no trend toward a particular apple cultivar supporting survival of E. coli O157:H7. However, variation in apple pH during storage can negatively or positively influence E. coli O157:H7 survival at 25 °C.

Effectiveness of Salt, pH, and Diacetyl as Inhibitors for Escherichia coli O157:H7 in Dairy Foods Stored at Refrigeration Temperatures

1998 ◽  
Vol 61 (9) ◽  
pp. 1098-1102 ◽  
Author(s):  
R. GURAYA ◽  
J. F. FRANK ◽  
A. N. HASSAN
Keyword(s):  
Escherichia Coli ◽  
Skim Milk ◽  
Cottage Cheese ◽  
Escherichia Coli O157 ◽  
Dairy Foods ◽  
E Coli ◽  
Dry Milk ◽  
Survival And Growth ◽  
Sour Cream ◽  
Temperature Levels

The behavior of Escherichia coli O157:H7 inoculated in 10% rehydrated nonfat dry milk adjusted to pH levels between 3.8 and 5.4 with lactic acid, salt levels of 0 to 6%, and diacetyl levels of 0, 5, and 10 μg/g was determined at 4 and 12°C. Cell populations were determined by surface plating on tryptic soy agar after 7 and 35 days of incubation. Survival was also determined using retad cultured dairy products. E. coli O157:H7 did not survive in skim milk at pH 3.8 and was reduced by 3 log cycles at pH 4.1, regardless of salt, diacetyl, and temperature levels. At pH levels above 4.4, survival was observed at lower salt concentrations for up to 35 days at both 12 and 4°C. The organism grew (up to a 2.2-log increase) at pH 5.0 at 2% salt levels after 35 days of storage at 12°C but not at 4°C. Diacetyl at a concentration of 10 ppm had no effect on survival and growth. In all but one case, E. coli O157:H7 was inactivated in yogurt, sour cream, and buttermilk at a rate similar to or greater than what was consistent with the acidified skim milk data. Also consistent with the skim milk data, growth occurred in two of the three cottage cheese samples at 12°C after 7 days but not after 35 days or at 4°C, when a 1- to 2-log decline was observed.

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