Surface Pasteurization of Whole Fresh Cantaloupes Inoculated with Salmonella Poona or Escherichia coli †

2004 ◽  
Vol 67 (9) ◽  
pp. 1876-1885 ◽  
Author(s):  
BASSAM A. ANNOUS ◽  
ANGELA BURKE ◽  
JOSEPH E. SITES
Keyword(s):  
Escherichia Coli ◽  
Room Temperature ◽  
Cell Concentration ◽  
Mold Growth ◽  
Human Pathogen ◽  
E Coli ◽  
Microbiological Safety ◽  
Commercial Scale ◽  
Final Cell Concentration ◽  
Scale Surface

Numerous outbreaks of salmonellosis by Salmonella Poona have been associated with the consumption of cantaloupe. Commercial washing processes for cantaloupe are limited in their ability to inactivate or remove this human pathogen. Our objective was to develop a commercial-scale surface pasteurization process to enhance the microbiological safety of cantaloupe. Populations of indigenous bacteria recovered from cantaloupes that were surface pasteurized at 96, 86, or 76°C for 2 to 3 min were significantly (P < 0.05) lower than those of the controls. Whole cantaloupes, surface inoculated with Salmonella Poona RM 2350 or Escherichia coli ATCC 25922 to a final cell concentration of ca. 5 log CFU/cm2 were stored at 4°C or room temperature (RT = 19 ± 1°C) for up to 72 h before processing. Treatments at 76°C for 2 to 3 min at 24 h postinoculation resulted in a reduction in excess of 5 log CFU/cm2 of Salmonella Poona and E. coli populations. Cantaloupes that were surface pasteurized and stored at 4°C for 21 days retained their firmness qualities and had no visible mold growth compared with the controls, which became soft and moldy. These results indicate that surface pasteurization will enhance the microbiological safety of cantaloupes and will extend the shelf life of this commodity as well. Storage of untreated inoculated cantaloupes at RT for 24 to 72 h postinoculation caused a significant (P < 0.05) increase in Salmonella Poona and E. coli populations compared with storage at 4°C. This indicates that cantaloupes should be refrigerated as soon as possible following harvest to suppress the growth of any possible contaminant on the rind.

Commercial Thermal Process for Inactivating Salmonella Poona on Surfaces of Whole Fresh Cantaloupes†

2013 ◽  
Vol 76 (3) ◽  
pp. 420-428 ◽  
Author(s):  
BASSAM A. ANNOUS ◽  
ANGELA BURKE ◽  
JOSEPH E. SITES ◽  
JOHN G. PHILLIPS
Keyword(s):  
Listeria Monocytogenes ◽  
Thermal Process ◽  
Hot Water ◽  
Processing Temperature ◽  
Human Pathogen ◽  
Microbiological Safety ◽  
Commercial Scale ◽  
Fresh Cut ◽  
Water Treatments ◽  
Scale Surface

Outbreaks of salmonellosis by Salmonella Poona and listeriosis by Listeria monocytogenes have been associated with the consumption of cantaloupes. Commercial washing processes for cantaloupes are limited in their ability to inactivate and/or remove this human pathogen. Our objective was to develop a commercial-scale surface pasteurization process for enhancing microbiological safety of cantaloupes. Whole cantaloupes, surface inoculated with Salmonella Poona RM 2350, were stored at 32°C for 24 h prior to processing. Temperature-penetration profiles indicated that the surface temperature of the whole cantaloupe was 26 and 30°C below that of the hot water temperature after 2 min of immersion at 82 and 92°C, respectively. Hot water treatments at 92°C for 60 and 90 s reduced Salmonella Poona populations in excess of 5 log CFU/g of rind. Cantaloupes that were treated and stored at 4°C for 9 days retained their firmness quality and maintained nondetectable levels of Salmonella Poona as compared with the controls. Also, levels of Salmonella Poona on fresh-cut cantaloupe prepared from hot water–treated cantaloupes and stored for 9 days at 4°C were nondetectable as compared with the controls. These results indicate that surface pasteurization at 92°C for 90 s will enhance the microbiological safety of cantaloupes and will extend the shelf life of this commodity as well. The process parameter of 90 s or less falls within the commercial requirements of the whole-cantaloupe processor-packer industry.

Validation of Time and Temperature Values as Critical Limits for the Control of Escherichia coli O157:H7 during the Production of Fresh Ground Beef

2006 ◽  
Vol 69 (8) ◽  
pp. 1978-1982 ◽  
Author(s):  
J. E. MANN ◽  
M. M. BRASHEARS
Keyword(s):  
Escherichia Coli ◽  
Room Temperature ◽  
Hazard Analysis ◽  
Control Point ◽  
Ground Beef ◽  
Escherichia Coli O157 ◽  
Meat Processing ◽  
E Coli ◽  
Critical Control Point ◽  
Critical Limits

In order to provide beef processors with valuable data to validate critical limits set for temperature during grinding, a study was conducted to determine Escherichia coli O157:H7 growth at various temperatures in raw ground beef. Fresh ground beef samples were inoculated with a cocktail mixture of streptomycin-resistant E. coli O157:H7 to facilitate recovery in the presence of background flora. Samples were held at 4.4, 7.2, and 10°C, and at room temperature (22.2 to 23.3°C) to mimic typical processing and holding temperatures observed in meat processing environments. E. coli O157:H7 counts were determined by direct plating onto tryptic soy agar with streptomycin (1,000 μg/ml), at 2-h intervals over 12 h for samples held at room temperature. Samples held under refrigeration temperatures were sampled at 4, 8, 12, 24, 48, and 72 h. Less than one log of E. coli O157:H7 growth was observed at 48 h for samples held at 10°C. Samples held at 4.4 and 7.2°C showed less than one log of E. coli O157:H7 growth at 72 h. Samples held at room temperature showed no significant increase in E. coli O157:H7 counts for the first 6 h, but increased significantly afterwards. These results illustrate that meat processors can utilize a variety of time and temperature combinations as critical limits in their hazard analysis critical control point plans to minimize E. coli O157:H7 growth during the production and storage of ground beef.

scholarly journals TOTAL Escherichia coli PADA SOSIS IKAN YANG DI-COATING DENGAN MIOFIBRIL ASAP CAIR SELAMA PENYIMPANAN

2016 ◽  
Vol 4 (1) ◽  
Author(s):  
Jupni Keno ◽  
Henny Adeleida Dien ◽  
Agnes Triasih Agustin
Keyword(s):  
Escherichia Coli ◽  
Nutritional Value ◽  
Room Temperature ◽  
Total Coliform ◽  
Fish Protein ◽  
Gram Negative ◽  
E Coli ◽  
Liquid Smoke ◽  
Refrigerator Temperature ◽  
Descriptive Method

Fish sausages are prepared foods that have a high nutritional value, but that is the weakness of this commodity is rapidly decaying nature. Bacterial pathogens that must be avoided include Escherichia coli. These bacteria are gram-negative, rod-shaped and motile spores are not. The purpose of this study is to calculate the total coliforms and E. coli in fish sausage coating of fish protein myofibrils Black Marlin (Makaira indica) during storage at room temperature (28–29°C), and refrigerator temperature (10–13°C). The method used is descriptive method, which is a study conducted to analyze an individual, the state, or the symptoms of a particular group. The results showed that the total coliform in fish sausage in coating with liquid smoke is stored at room temperature, the lowest value is 7 MPN/g, the highest of 120 MPN/g, while the lowest value refrigerator temperature is 7 MPN/g, the highest 93 MPN/g. Total coliform in fish sausage in smokeless liquid coating stored at room temperature with the lowest value is 7 MPN/g, the highest 210 MPN/g, while the lowest value refrigerator temperature is 7 MPN/g, and the highest is 120 MPN/g. Total coliform in fish sausages are not in the coating deposited at room temperature with the lowest value is 7 MPN/g, the highest of 240 MPN/g, at refrigerator temperature the lowest value is 7 MPN/g, and the highest is 150 MPN/g. Total E. coli showed that the fish sausage in coating with liquid smoke is stored at room temperature, the lowest value is 1 MPN/g, and the highest is 4 MPN/g, while the lowest value refrigerator temperature is <3 MPN/g, and The highest is 3 MPN/g. Total E. coli in fish sausage in smokeless coating liquid stored at room temperature, the lowest value is 2 MPN/g, and the highest is 4 MPN/g, while the temperature of the refrigerator lowest value is 1 MPN/g, and a high of 3 MPN/g. Total E. coli in sausages are not in the coating deposited at room temperature, the lowest value is 2 MPN/g, and the highest is 5 MPN/g, and the refrigerator temperature is the lowest rating 2 MPN/g, the highest is 4 MPN/g during storage .Keywords: fish sausage, coating, myofibril, Eschericia coli.  Sosis ikan merupakan makanan siap saji yang mempunyai nilai gizi tinggi, namun yang menjadi kelemahan dari komoniti ini adalah sifatnya yang cepat membusuk. Bakteri patogen yang harus dihindari antara lain Escherichia coli.  Bakteri ini bersifat gram negatif, berbentuk batang tidak spora dan bersifat motil. Tujuan penelitian ini yaitu untuk menghitung total koliform dan E. coli pada sosis ikan yang dicoating dari miofibril protein ikan Black Marlin (Makaira indica) selama penyimpanan suhu ruang (28–29°C), dan suhu kulkas (10–13°C). Metode penelitian yang digunakan adalah metode deskriptif, yaitu suatu penelitian yang dilakukan untuk menganalisa suatu individu, keadaan, gejala atau kelompok tertentu. Hasil penelitian menunjukkan bahwa total koliform pada sosis ikan yang dicoating dengan asap cair disimpan pada suhu ruang, nilai terendah yaitu 7 MPN/g, tertinggi 120 MPN/g, sedangkan pada suhu kulkas nilai yang terendah yaitu 7 MPN/g, tertinggi 93 MPN/g. Total koliform pada sosis ikan yang dicoating tanpa asap cair disimpan pada suhu ruang dengan nilai terendah yaitu 7 MPN/g, tertinggi 210 MPN/g, sedangkan pada suhu kulkas nilai yang terendah yaitu 7 MPN/g, dan tertinggi 120 MPN/g. Total koliform pada sosis ikan tidak dicoating disimpan pada suhu ruang dengan nilai terendah yaitu 7 MPN/g, tertinggi 240 MPN/g , pada suhu kulkas nilai terendah yaitu 7 MPN/g , dan tertinggi 150 MPN/g. Total E. coli menunjukkan bahwa pada sosis ikan yang dicoating dengan asap cair disimpan pada suhu ruang, yaitu nilai terendah 3 MPN/g, dan tertinggi 4 MPN/g, sedangkan pada suhu kulkas nilai terendah yaitu <3 MPN/g, dan tertinggi 3 MPN/g. Total E. coli pada sosis ikan yang dicoating tanpa asap cair disimpan pada suhu ruang, yaitu nilai terendah 3 MPN/g, dan tertinggi 4 MPN/g, sedangkan pada suhu kulkas nilai terendah yaitu <3 MPN/g , dan tertinggi 3 MPN/g. Total E. coli pada sosis tidak dicoatingdisimpan pada suhu ruang, yaitu nilai terendah 4 MPN/g, dan tertinggi 7 MPN/g, dan pada suhu kulkas yaitu nilai terendah 3 MPN/g, tertinggi 4 MPN/g selama penyimpanan.Kata kunci: sosis ikan, coating, myofibril, Eschericia coli.

scholarly journals Transfer of Escherichia Coli to Lemons Slices and Ice during Handling

2017 ◽  
Vol 6 (4) ◽  
pp. 111
Author(s):  
Paul Dawson ◽  
Inyee Han ◽  
Ahmet Buyukyavuz ◽  
Wesam Aljeddawi ◽  
Rose Martinez-Dawson ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Room Temperature ◽  
Separate Experiment ◽  
E Coli ◽  
And Storage ◽  
Growth Of Bacteria

The objective of this study was to determine the transfer and survival of bacteria during the handling and storage of lemons and transfer of bacteria during handling of ice. Ice and lemon slices are handled and stored in public eating places and used in beverages. During handling and storage the contamination and growth of bacteria may occur leading to the spread of disease. To fulfill the objective, hands were inoculated with Escherichia coli prior to handling of wet and dry whole lemons and in a separate experiment, ice cubes were handled. E. coli transferred to whole lemons or ice after handling were determined. The CFU per lemon and percentage of E. coli transferred were greater for wet lemons -6123 cfu and 4.62% compared to 469 cfu and .2% for dry lemons. The second experiment found from 2 to 67% of the bacteria on hands were transferred to ice by hands and from 30 to 83% of the bacteria on scoops were transferred to ice. In a third experiment, lemons were inoculated with E. coli, then sliced and stored at 4 or 22C and tested at 0, 4 and 24 hr. Lemons stored at room temperature (22°C) had an increase in E. coli population after 24 hour while those stored under refrigeration had a decrease even though bacteria did survive on lemons in either case. 

Different responses to nitrate and nitrite by the model organism Escherichia coli and the human pathogen Neisseria gonorrhoeae

2006 ◽  
Vol 34 (1) ◽  
pp. 111-114 ◽  
Author(s):  
R.N. Whitehead ◽  
J.A. Cole
Keyword(s):  
Escherichia Coli ◽  
Neisseria Gonorrhoeae ◽  
Model Organism ◽  
Anaerobic Growth ◽  
Human Pathogen ◽  
Regulate Gene Expression ◽  
E Coli ◽  
Regulatory Systems ◽  
Two Component ◽  
Nitrate And Nitrite

The ability of Escherichia coli to use both nitrate and nitrite as terminal electron acceptors during anaerobic growth is mediated by the dual-acting two-component regulatory systems NarX-NarL and NarQ-NarP. In contrast, Neisseria gonorrhoeae responds only to nitrite: it expresses only NarQ-NarP. We have shown that although N. gonorrhoeae NarQ can phosphorylate E. coli NarL and NarP, the N. gonorrhoeae NarP is unable to regulate gene expression in E. coli. Mutagenesis experiments have revealed residues in E. coli NarQ that are essential for nitrate and nitrite sensing. Chimaeric proteins revealed domains of NarQ that are important for ligand sensing.

scholarly journals The Impact of Plasma Membrane Lipid Composition on Flagellum-Mediated Adhesion of Enterohemorrhagic Escherichia coli

mSphere ◽  
2020 ◽  
Vol 5 (5) ◽  
Author(s):  
Hélène Cazzola ◽  
Laurine Lemaire ◽  
Sébastien Acket ◽  
Elise Prost ◽  
Luminita Duma ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Plasma Membrane ◽  
Fatty Acid ◽  
Linolenic Acid ◽  
Lipid Rafts ◽  
Bacterial Adhesion ◽  
Human Pathogen ◽  
Content Type ◽  
E Coli ◽  
The Impact

ABSTRACT Enterohemorrhagic Escherichia coli (EHEC) O157:H7 is a major cause of foodborne gastrointestinal illness. The adhesion of EHEC to host tissues is the first step enabling bacterial colonization. Adhesins such as fimbriae and flagella mediate this process. Here, we studied the interaction of the bacterial flagellum with the host cell’s plasma membrane using giant unilamellar vesicles (GUVs) as a biologically relevant model. Cultured cell lines contain many different molecular components, including proteins and glycoproteins. In contrast, with GUVs, we can characterize the bacterial mode of interaction solely with a defined lipid part of the cell membrane. Bacterial adhesion on GUVs was dependent on the presence of the flagellar filament and its motility. By testing different phospholipid head groups, the nature of the fatty acid chains, or the liposome curvature, we found that lipid packing is a key parameter to enable bacterial adhesion. Using HT-29 cells grown in the presence of polyunsaturated fatty acid (α-linolenic acid) or saturated fatty acid (palmitic acid), we found that α-linolenic acid reduced adhesion of wild-type EHEC but not of a nonflagellated mutant. Finally, our results reveal that the presence of flagella is advantageous for the bacteria to bind to lipid rafts. We speculate that polyunsaturated fatty acids prevent flagellar adhesion on membrane bilayers and play a clear role for optimal host colonization. Flagellum-mediated adhesion to plasma membranes has broad implications for host-pathogen interactions. IMPORTANCE Bacterial adhesion is a crucial step to allow bacteria to colonize their hosts, invade tissues, and form biofilm. Enterohemorrhagic Escherichia coli O157:H7 is a human pathogen and the causative agent of diarrhea and hemorrhagic colitis. Here, we use biomimetic membrane models and cell lines to decipher the impact of lipid content of the plasma membrane on enterohemorrhagic E. coli flagellum-mediated adhesion. Our findings provide evidence that polyunsaturated fatty acid (α-linolenic acid) inhibits E. coli flagellar adhesion to the plasma membrane in a mechanism separate from its antimicrobial and anti-inflammatory functions. In addition, we confirm that cholesterol-enriched lipid microdomains, often called lipid rafts, are important in bacterial adhesion. These findings demonstrate that plasma membrane adhesion via bacterial flagella play a significant role for an important human pathogen. This mechanism represents a promising target for the development of novel antiadhesion therapies.

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.

Effects of Selected Cooking Procedures on the Survival of Escherichia coli O157:H7 in Inoculated Steaks Cooked on a Hot Plate or Gas Barbecue Grill

2014 ◽  
Vol 77 (6) ◽  
pp. 919-926 ◽  
Author(s):  
C. O. GILL ◽  
J. DEVOS ◽  
M. K. YOUSSEF ◽  
X. YANG
Keyword(s):  
Escherichia Coli ◽  
Central Plane ◽  
Escherichia Coli O157 ◽  
Hot Plate ◽  
E Coli ◽  
Microbiological Safety ◽  
Beef Steaks

Beef steaks (2 cm thick) were each inoculated at three sites in the central plane with Escherichia coli O157:H7 at 5.9 ± 0.3 log CFU per site. Temperatures at steak centers were monitored during cooking on a hot plate or the grill of a gas barbeque. Steaks were cooked in groups of five using the same procedures and cooking each steak to the same temperature, and surviving E. coli O157:H7 at each site was enumerated. When steaks cooked on the hot plate were turned over every 2 or 4 min during cooking to between 56 and 62°C, no E. coli O157:H7 was recovered from steaks cooked to ≥58 or 62°C, respectively. When steaks were cooked to ≤71°C and turned over once during cooking, E. coli O157:H7 was recovered from steaks in groups turned over after ≤8 min but not from steaks turned over after 10 or 12 min. E. coli O157:H7 was recovered in similar numbers from steaks that were not held or were held for 3 min after cooking when steaks were turned over once after 4 or 6 min during cooking. When steaks were cooked on the grill with the barbeque lid open and turned over every 2 or 4 min during cooking to 63 or 56°C, E. coli O157:H7 was recovered from only those steaks turned over at 4-min intervals and cooked to 56°C. E. coli O157:H7 was recovered from some steaks turned over once during cooking on the grill and held or not held after cooking to 63°C. E. coli O157:H7 was not recovered from steaks turned over after 4 min during cooking to 60°C on the grill with the barbeque lid closed or when the lid was closed after 6 min. Apparently, the microbiological safety of mechanically tenderized steaks can be assured by turning steaks over at intervals of about 2 min during cooking to ≥60°C in an open skillet or on a barbecue grill. When steaks are turned over only once during cooking to ≥60°C, microbiological safety may be assured by covering the skillet or grill with a lid during at least the final minutes of cooking.

Real-Time Bioluminescence Analysis of Escherichia coli O157:H7 Survival on Livestock Meats Stored Fresh, Cold, or Frozen

2018 ◽  
Vol 81 (11) ◽  
pp. 1906-1912 ◽  
Author(s):  
SEONG B. PARK ◽  
SHECOYA B. WHITE ◽  
CHRISTY S. STEADMAN ◽  
CLAY A. CAVINDER ◽  
SCOTT T. WILLARD ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Real Time ◽  
Bacterial Growth ◽  
Room Temperature ◽  
Storage Conditions ◽  
Escherichia Coli O157 ◽  
Production Environment ◽  
Real Time Monitoring ◽  
E Coli ◽  
C Storage

ABSTRACT Foodborne bacteria such as Escherichia coli O157:H7 can cause severe hemorrhagic colitis in humans following consumption of contaminated meat products. Contamination with pathogenic bacteria is frequently found in the food production environment, and adequate household storage conditions of purchased foods are vital for illness avoidance. Real-time monitoring was used to evaluate bacterial growth in ground horse, beef, and pork meats maintained under various storage conditions. Various levels of E. coli O157:H7 carrying the luxCDABE operon, which allows the cells to emit bioluminescence, were used to inoculate meat samples that were then stored at room temperature for 0.5 day, at 4°C (cold) for 7 or 9 days, or −20°C (frozen) for 9 days. Real-time bioluminescence imaging (BLI) of bacterial growth was used to assess bacterial survival or load. Ground horse meat BLI signals and E. coli levels were dose and time dependent, increasing during room temperature and −20°C storage, but stayed at low levels during 4°C storage. No bacteria survived in the lower level inoculum groups (101 and 103 CFU/g). With an inoculum of 107 CFU/g, pork meats had higher BLI signals than did their beef counterparts, displaying decreased BLI signals during 7 days storage at 4°C. Both meat types had higher BLI signals in the fat area, which was confirmed with isolated fat tissues in the beef meat. Beef lean and fat tissues contrasted with both pork fat and lean tissues, which had significantly higher BLI signals and bacterial levels. BLI appears to be a useful research tool for real-time monitoring of bacterial growth and survival in various stored livestock meats. The dependence of E. coli O157:H7 growth on meat substrate (fat or lean) and storage conditions may be used as part of an effective antibacterial approach for the production of safe ground horse, beef, and pork meats.

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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