scholarly journals Modelling Growth and Decline in a Two-Species Model System: Pathogenic Escherichia coli O157:H7 and Psychrotrophic Spoilage Bacteria in Milk

Foods ◽  
2020 ◽  
Vol 9 (3) ◽  
pp. 331 ◽  
Author(s):  
Emiliano J. Quinto ◽  
Juan M. Marín ◽  
Irma Caro ◽  
Javier Mateo ◽  
Donald W. Schaffner
Keyword(s):  
Escherichia Coli ◽  
Foodborne Pathogens ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Food Borne ◽  
Pathogenic Escherichia Coli ◽  
Spoilage Bacteria ◽  
Processing And Storage ◽  
And Storage ◽  
Natural Microbiota

Shiga toxin-producing Escherichia coli O157:H7 is a food-borne pathogen and the major cause of hemorrhagic colitis. Pseudomonas is the genus most frequent psychrotrophic spoilage microorganisms present in milk. Two-species bacterial systems with E. coli O157:H7, non-pathogenic E. coli, and P. fluorescens in skimmed milk at 7, 13, 19, or 25 °C were studied. Bacterial interactions were modelled after applying a Bayesian approach. No direct correlation between P. fluorescens’s growth rate and its effect on the maximum population densities of E. coli species was found. The results show the complexity of the interactions between two species in a food model. The use of natural microbiota members to control foodborne pathogens could be useful to improve food safety during the processing and storage of refrigerated foods.

Survival of Escherichia coli O157:H7 in Set Yogurt as Influenced by the Production of an Exopolysaccharide, Colanic Acid

2004 ◽  
Vol 67 (2) ◽  
pp. 252-255 ◽  
Author(s):  
SHIAO MEI LEE ◽  
JINRU CHEN
Keyword(s):  
Escherichia Coli ◽  
Culture Media ◽  
Starter Cultures ◽  
Escherichia Coli O157 ◽  
Acidic Polysaccharide ◽  
E Coli ◽  
Colanic Acid ◽  
Plate Counts ◽  
Processing And Storage ◽  
And Storage

Previous studies conducted in our laboratory revealed that Escherichia coli O157:H7 cells capable of producing colanic acid (CA), the acidic polysaccharide of mucoid slime, had increased tolerance to sublethal heat and the extreme pH of microbiological culture media. This study was undertaken to determine the effect of CA on the fate of E. coli O157:H7 during the processing and storage of an acid food: yogurt. Pasteurized and homogenized whole milk was inoculated with a wild-type E. coli O157:H7, its CA-deficient mutant, or a mixture (1:1) of the two strains. Set yogurt was processed from the contaminated milk and stored at 4° and 15°C for 3 weeks. Samples of milk and yogurt were withdrawn during processing and storage and analyzed for total plate counts and populations of E. coli O157:H7 and starter cultures. The results showed that E. coli O157: H7 survived longer in yogurt stored at 15°C than at 4°C. Cells of E. coli O157:H7 deficient in CA production died off more rapidly than those of the parent strain. This suggests that CA plays a role in protecting cells of E. coli O157:H7 from stress during the processing and storage of set yogurt.

scholarly journals Growth of Salmonella and Other Foodborne Pathogens on Inoculated Inshell Pistachios during Simulated Delays between Hulling and Drying

2019 ◽  
Vol 82 (5) ◽  
pp. 815-825 ◽  
Author(s):  
MAHTA MOUSSAVI ◽  
VANESSA LIEBERMAN ◽  
CHRIS THEOFEL ◽  
JAVAD BAROUEI ◽  
LINDA J. HARRIS
Keyword(s):  
Escherichia Coli ◽  
Relative Humidity ◽  
Foodborne Pathogens ◽  
Lag Time ◽  
Escherichia Coli O157 ◽  
Contributing Factors ◽  
Shell Surface ◽  
E Coli ◽  
Significant Growth ◽  
Lower Maximum

ABSTRACT During harvest, pistachios are hulled, separated in water into floater and sinker streams (in large part on the basis of nut density), and then dried before storage. Higher prevalence and levels of Salmonella were previously observed in floater pistachios, but contributing factors are unclear. To examine the behavior of pathogens on hulled pistachios during simulated drying delays, floater and sinker pistachios collected from commercial processors were inoculated at 1 or 3 log CFU/g with cocktails of Salmonella and in some cases Escherichia coli O157:H7 or Listeria monocytogenes and incubated for up to 30 h at 37°C and 90% relative humidity. Populations were measured by plating onto tryptic soy agar and appropriate selective agars. In most cases, no significant growth (P > 0.05) of Salmonella was observed in the first 3 h after inoculation in hulled floaters and sinkers. Growth of Salmonella was greater on floater pistachios than on corresponding sinkers and on floater pistachios with ≥25% hull adhering to the shell surface than on corresponding floaters with <25% adhering hull. Maximum Salmonella populations (2 to 7 log CFU/g) were ∼2-log higher on floaters than on corresponding sinkers. The growth of E. coli O157:H7 and Salmonella on hulled pistachios was similar, but a longer lag time (approximately 11 h) and significantly lower maximum populations (4 versus 5 to 6 log CFU/g; P < 0.05) were predicted for L. monocytogenes. Significant growth of pathogens on hulled pistachios is possible when delays between hulling and drying are longer than 3 h, and pathogen growth is enhanced in the presence of adhering hull material.

Inactivation of Escherichia coli O157:H7 and Salmonella and Native Microbiota on Fresh Strawberries by Antimicrobial Washing and Coating

2018 ◽  
Vol 81 (8) ◽  
pp. 1227-1235 ◽  
Author(s):  
MINGMING GUO ◽  
TONY Z. JIN ◽  
JOSHUA B. GURTLER ◽  
XUETONG FAN ◽  
MADHAV P. YADAV
Keyword(s):  
Escherichia Coli ◽  
Foodborne Pathogens ◽  
Allyl Isothiocyanate ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Native Microflora ◽  
Pathogen Populations ◽  
Antimicrobial Treatments ◽  
Antimicrobial Effectiveness

ABSTRACT Antimicrobial washing (AW), antimicrobial coating (AC), and a combination of washing followed by coating (AW+AC) were evaluated for their ability to inactivate artificially inoculated foodborne pathogens and native microbiota on strawberries stored at 4°C. Strawberries were inoculated with a six-strain composite of Escherichia coli O157:H7 and Salmonella; treated by AW, AC, or AW+AC; and stored at 4°C for 3 weeks. The washing solution contained 90 ppm of peracetic acid, and the coating solution consisted of chitosan (1%, w/v), allyl isothiocyanate (1%, v/v), and corn-bio fiber gum (5%, w/v). The effectiveness of the antimicrobial treatments against E. coli O157:H7 and Salmonella pathogens and native microflora on strawberries and their impact on fruit quality (appearance, weight loss, color, and firmness) were determined. By the end of storage, pathogen populations on strawberries were 2.5 (AW+AC), 2.9 (AC), 3.8 (AW), and 4.2 log CFU for the positive (untreated) control. AW+AC treatments also inactivated the greatest population of native microflora, followed by the AC treatment alone. AW+AC treatments showed additional antimicrobial effectiveness against these two pathogens and native microflora. Both AW+AC and AC treatments preserved the color, texture, and appearance of strawberries throughout storage. The coating treatments (AW+AC and AC alone) further reduced the loss of moisture throughout storage. The AW treatment was the least effective in reducing populations of pathogens and native microflora and in maintaining the quality of strawberries throughout storage. This study demonstrates a method to improve the microbiological safety, shelf life, and quality of strawberries.

Rapid and Sensitive Detection of Escherichia coli O157:H7 in Milk and Ground Beef Using Magnetic Bead–Based Immunoassay Coupled with Tyramide Signal Amplification

2014 ◽  
Vol 77 (1) ◽  
pp. 100-105 ◽  
Author(s):  
MUHSIN AYDIN ◽  
GENE P. D. HERZIG ◽  
KWANG CHEOL JEONG ◽  
SAMANTHA DUNIGAN ◽  
PARTH SHAH ◽  
...  
Keyword(s):  
Public Health ◽  
Escherichia Coli ◽  
Food Safety ◽  
Foodborne Pathogens ◽  
Signal Amplification ◽  
Magnetic Bead ◽  
Escherichia Coli O157 ◽  
Tyramide Signal Amplification ◽  
E Coli ◽  
Enrichment Step

Escherichia coli O157:H7 is a major foodborne pathogen that has posed serious problems for food safety and public health. Recent outbreaks and recalls associated with various foods contaminated by E. coli O157:H7 clearly indicate its deleterious effect on food safety. A rapid and sensitive detection assay is needed for this harmful organism to prevent foodborne illnesses and control outbreaks in a timely manner. We developed a magnetic bead–based immunoassay for detection of E. coli O157:H7 (the most well-known Shiga toxigenic E. coli strain) with a 96-well microplate as an assay platform. Immunomagnetic separation (IMS) and tyramide signal amplification were coupled to the assay to increase its sensitivity and specificity. This immunoassay was able to detect E. coli O157:H7 in pure culture with a detection limit of 50 CFU/ml in less than 3 h without an enrichment step. The detection limit was decreased 10-fold to 5 CFU/ml with addition of a 3-h enrichment step. When this assay was tested with other nontarget foodborne pathogens and common enteric bacteria, no cross-reactivity was found. When tested with artificially contaminated ground beef and milk samples, the assay sensitivity decreased two- to fivefold, with detection limits of 250 and 100 CFU/ml, respectively, probably because of the food matrix effect. The assay results also were compared with those of a sandwich-type enzyme-linked immunosorbent assay (ELISA) and an ELISA coupled with IMS; the developed assay was 25 times and 4 times more sensitive than the standard ELISA and the IMS-ELISA, respectively. Tyramide signal amplification combined with IMS can improve sensitivity and specificity for detection of E. coli O157:H7. The developed assay could be easily adapted for other foodborne pathogens and will contribute to improved food safety and public health.

Inactivation of Escherichia coli O157:H7 and Listeria monocytogenes on Plastic Kitchen Cutting Boards by Electrolyzed Oxidizing Water

1999 ◽  
Vol 62 (8) ◽  
pp. 857-860 ◽  
Author(s):  
KUMAR S. VENKITANARAYANAN ◽  
GABRIEL O. I. EZEIKE ◽  
YEN-CON HUNG ◽  
MICHAEL P. DOYLE
Keyword(s):  
Escherichia Coli ◽  
Listeria Monocytogenes ◽  
Laminar Flow ◽  
Foodborne Pathogens ◽  
Deionized Water ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Laminar Flow Hood ◽  
Cutting Boards ◽  
Temperature Time

One milliliter of culture containing a five-strain mixture of Escherichia coli O157:H7 (∼1010 CFU) was inoculated on a 100-cm2 area marked on unscarred cutting boards. Following inoculation, the boards were air-dried under a laminar flow hood for 1 h, immersed in 2 liters of electrolyzed oxidizing water or sterile deionized water at 23°C or 35°C for 10 or 20 min; 45°C for 5 or 10 min; or 55°C for 5 min. After each temperature–time combination, the surviving population of the pathogen on cutting boards and in soaking water was determined. Soaking of inoculated cutting boards in electrolyzed oxidizing water reduced E. coli O157:H7 populations by ≥5.0 log CFU/100 cm2 on cutting boards. However, immersion of cutting boards in deionized water decreased the pathogen count only by 1.0 to 1.5 log CFU/100 cm2. Treatment of cutting boards inoculated with Listeria monocytogenes in electrolyzed oxidizing water at selected temperature–time combinations (23°C for 20 min, 35°C for 10 min, and 45°C for 10 min) substantially reduced the populations of L. monocytogenes in comparison to the counts recovered from the boards immersed in deionized water. E. coli O157:H7 and L. monocytogenes were not detected in electrolyzed oxidizing water after soaking treatment, whereas the pathogens survived in the deionized water used for soaking the cutting boards. This study revealed that immersion of kitchen cutting boards in electrolyzed oxidizing water could be used as an effective method for inactivating foodborne pathogens on smooth, plastic cutting boards.

Reduction of Listeria monocytogenes and Escherichia coli O157:H7 Numbers on Vacuum-Packaged Fresh Beef Treated with Nisin or Nisin Combined with EDTA†

1999 ◽  
Vol 62 (10) ◽  
pp. 1123-1127 ◽  
Author(s):  
SHANSHAN ZHANG ◽  
AZLIN MUSTAPHA
Keyword(s):  
Escherichia Coli ◽  
Listeria Monocytogenes ◽  
Bacterial Growth ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Key Factor ◽  
Vacuum Package ◽  
And Storage

Nisin or nisin combined with EDTA was used to treat fresh beef. Beef cubes (2.5 by 2.5 by 2.5 cm) that were inoculated with approximately 7 log CFU/ml of Listeria monocytogenes Scott A or Escherichia coli O157:H7 505 B were dipped in the following solutions: (i) H2O, (ii) HCl, (iii) nisin, (iv) EDTA, or (v) nisin combined with EDTA, respectively, for 10 min each, with an exception of one set of control beef samples without treatment. Beef samples were then drip-dried for 15 min, vacuum packaged, and stored at 4°C for up to 30 days. The pH on beef after different treatments was not a key factor in preventing bacterial growth. Treatment with nisin or with nisin combined with EDTA reduced the population of L. monocytogenes by 2.01 and 0.99 log CFU/cm2 as compared to the control, respectively, under the conditions of vacuum package and storage at 4°C for up to 30 days. However, the effect of nisin and nisin combined with EDTA against E. coli O157:H7 505 B was marginal at 1.02 log CFU/cm2 and 0.8 log CFU/cm2 reductions, respectively.

scholarly journals Survival of Shiga Toxin-Producing Escherichia coli (STEC) Serogroups During Production and Storage of Yogurt

2021 ◽  
Vol 72 (1) ◽  
pp. 2689
Author(s):  
G CELIK ◽  
A DIKICI ◽  
A KOLUMAN
Keyword(s):  
Escherichia Coli ◽  
Shiga Toxin ◽  
Starter Culture ◽  
Escherichia Coli O157 ◽  
Potential Health ◽  
Potential Health Risk ◽  
E Coli ◽  
Lactic Acid Content ◽  
And Storage ◽  
Lactobacillus Spp

In this study, the survival of Escherichia coli O157:H7 and non-O157 STEC serogroups of O26, O111, O103, and O145 were investigated during production and storage of yogurt. For this purpose, pathogens were individually inoculated into milk after pasteurization along with the starter culture (approximately 7.00±1.00 log10 cfu/g). After incubation at 44oC (about 180 min), yogurt samples were capped and stored at 4oC for 20 days. Pathogens were enumerated at 0, 5, 10, 15, and 20th days of storage. Lactic acid content (%) and pH of the samples were also screened. Moreover, mesophilic Lactococcus spp. and mesophilic Lactobacillus spp. were enumerated during production of yogurt.After incubation, the number of E. coli O157, O26, O103, O145, O111were 6.76±0.45, 6.64±0.53, 7.12±0.43, 6.00±1.39, 5.89±1.37 log10 cfu/g, respectively. A significant decrease was determined in all groups during the storage of yogurt samples at 4oC (p<0.05). It was detected on the 20th day of storage that the number of E. coli O157:H7 and non-O157 STEC serogroups of O103 and O145 were under the detection limit. However, STEC O26 and O111 were viable around 1.51±0.98 and 1.18±0.62 log10 cfu/g respectively. Results of the study showed that Escherichia coli O157:H7 and non-O157 STEC serogroups might pose a potential health risk during production and storage of yogurt.

Synergistic Effect of High Temperature and High pH on the Destruction of Salmonella enteritidis and Escherichia co1i O157:H7

1996 ◽  
Vol 59 (10) ◽  
pp. 1023-1030 ◽  
Author(s):  
YEOW-LIM TEO ◽  
TIMOTHY J. RAYNOR ◽  
KAMESWAR R. ELLAJOSYULA ◽  
STEPHEN J. KNABEL
Keyword(s):  
Escherichia Coli ◽  
High Temperature ◽  
Synergistic Effect ◽  
Foodborne Pathogens ◽  
Salmonella Enteritidis ◽  
Synergistic Interaction ◽  
Escherichia Coli O157 ◽  
Gram Negative ◽  
High Ph ◽  
E Coli

This study was undertaken to determine if high temperature and high pH interact synergistically to enhance the rate of destruction of two important gram-negative foodborne pathogens, Escherichia coli O157:H7 and Salmonella enteritidis. The rates of destruction in NaHCO3-NaOH buffers at pH 7.0, 10.0, and 11.0 were determined at 35, 40, 45, 50, 55, 60, and 65°C. Use of an improved heating protocol eliminated a “tailing effect” at longer exposure times. The present study demonstrated that the combination of high pH and high temperature resulted in a highly significant synergistic interaction (P &gt; F = 0.0001), which caused rapid death of both E. coli O157:H7 and S. enteritidis. This “alka-therm” technology might be used commercially to destroy gram-negative foodborne pathogens on various raw agricultural commodities.

Quantitative Microbial Risk Assessment for Escherichia coli O157:H7 in Fresh-Cut Lettuce

2017 ◽  
Vol 80 (2) ◽  
pp. 302-311 ◽  
Author(s):  
Hao Pang ◽  
Elisabetta Lambertini ◽  
Robert L. Buchanan ◽  
Donald W. Schaffner ◽  
Abani K. Pradhan
Keyword(s):  
Escherichia Coli ◽  
Foodborne Pathogens ◽  
The United States ◽  
Intervention Strategies ◽  
Sensitivity Analyses ◽  
Escherichia Coli O157 ◽  
Baseline Model ◽  
Microbial Risk ◽  
E Coli ◽  
Fresh Cut

ABSTRACT Leafy green vegetables, including lettuce, are recognized as potential vehicles for foodborne pathogens such as Escherichia coli O157:H7. Fresh-cut lettuce is potentially at high risk of causing foodborne illnesses, as it is generally consumed without cooking. Quantitative microbial risk assessments (QMRAs) are gaining more attention as an effective tool to assess and control potential risks associated with foodborne pathogens. This study developed a QMRA model for E. coli O157:H7 in fresh-cut lettuce and evaluated the effects of different potential intervention strategies on the reduction of public health risks. The fresh-cut lettuce production and supply chain was modeled from field production, with both irrigation water and soil as initial contamination sources, to consumption at home. The baseline model (with no interventions) predicted a mean probability of 1 illness per 10 million servings and a mean of 2,160 illness cases per year in the United States. All intervention strategies evaluated (chlorine, ultrasound and organic acid, irradiation, bacteriophage, and consumer washing) significantly reduced the estimated mean number of illness cases when compared with the baseline model prediction (from 11.4- to 17.9-fold reduction). Sensitivity analyses indicated that retail and home storage temperature were the most important factors affecting the predicted number of illness cases. The developed QMRA model provided a framework for estimating risk associated with consumption of E. coli O157:H7–contaminated fresh-cut lettuce and can guide the evaluation and development of intervention strategies aimed at reducing such risk.

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