Effect of Ph On Survival of Escherichia coli O157, Escherichia coli O121, and Salmonella enterica During Desiccation and Short-term Storage

2020 ◽  
Vol 83 (2) ◽  
pp. 211-220 ◽  
Author(s):  
QUINCY J. SUEHR ◽  
FANGYU CHEN ◽  
NATHAN M. ANDERSON ◽  
SUSANNE E. KELLER
Keyword(s):  
Escherichia Coli ◽  
Salmonella Enterica ◽  
Growth Conditions ◽  
Escherichia Coli O157 ◽  
Acid Adaptation ◽  
E Coli ◽  
Solid Media ◽  
Low Moisture Foods ◽  
Subsequent Storage ◽  
Intrinsic Characteristic

ABSTRACT One intrinsic characteristic of low-moisture foods that is frequently overlooked is pH. Although pH affects the survival of microorganisms in high-moisture foods, its influence in low-moisture foods with less available moisture has not been examined. Escherichia coli O157:H7, E. coli O121, Salmonella enterica Anatum, and S. enterica Agona were grown on solid media with and without added glucose, harvested, and then suspended in buffer at pH 4, 5, and 7 for 10 min. All cultures were spotted individually onto cellulose filters and dried in a biohazard cabinet (23 ± 2°C) overnight (24 ± 2 h) and then stored in a 25°C incubator at 33% relative humidity. Populations were examined at regular intervals up to 26 (E. coli) or 29 (Salmonella) days. Additional controls for pH consisted of cultures held in buffer at pH 4, 5, and 7 at 25°C for the same time periods as the desiccated cells. For all strains tested, pH had an effect on survival whether stored dried or in liquid buffer (P < 0.05). However, when grown on solid media, acid adaptation (grown with glucose) before acid treatment did not appear beneficial to Salmonella during desiccation. Instead, both acid-adapted Salmonella serovars appeared less resistant during drying than did non–acid-adapted cells. Once dried, the rates of decline for Salmonella were not significantly different for acid-adapted and nonadapted cells (P > 0.05), indicating similar persistence following desiccation. A reverse trend was observed for E. coli O121; acid adaptation on solid media improved survival during desiccation and subsequent storage at low pH (P < 0.05). E. coli O157:H7 survival was significantly lower than that of either Salmonella or E. coli O121 under all conditions tested. Results indicate that the response to desiccation and pH stress differs between the microorganisms and under different growth conditions. HIGHLIGHTS

Relationship of growth conditions to desiccation tolerance of Salmonella enterica, Escherichia coli, and Listeria monocytogenes

2021 ◽  
Author(s):  
Rachel K Streufert ◽  
Susanne E Keller ◽  
Joelle K Salazar
Keyword(s):  
Escherichia Coli ◽  
Listeria Monocytogenes ◽  
Desiccation Tolerance ◽  
Salmonella Enterica ◽  
Growth Conditions ◽  
Initial Population ◽  
Desiccation Resistance ◽  
E Coli ◽  
Solid Media ◽  
Agar Media

Growth on solid media as sessile cells is believed to increase the desiccation tolerance of Salmonella enterica . However, the reasons behind increased resistance have not been well explored. In addition, the same effect has not been examined for other foodborne pathogens such as pathogenic Escherichia coli or Listeria monocytogenes . The purpose of this research was two-fold: first, to determine the role of oxygenation during growth on the desiccation resistance of S. enterica , E. coli , and L. monocytogenes , and second, to determine the effect of sessile versus planktonic growth on the desiccation resistance of these pathogens. Three different serotypes each of Salmonella , E. coli , and L. monocytogenes were cultured in trypticase soy broth with 0.6% yeast extract (TSBYE), with (aerobic) shaking or on TSBYE with agar (TSAYE) under either aerobic or anaerobic conditions and harvested in stationary phase. After adding cell suspensions to cellulose filter disks, pathogen survival was determined by enumeration at 0 and after drying for 24 h. Results showed statistical differences in harvested initial populations prior to drying (0 h). For Salmonella , a correlation was found between high initial population and greater survival on desiccation (p = 0.05). In addition, statistical differences (p ≤ 0.05) between survival based on growth type were identified. However, differences found were not the same for the three pathogens, or between their serotypes. In general, Salmonella and E. coli desiccation resistance followed the pattern of aerobic agar media ≥ liquid media ≥ anaerobic agar media. For L. monocytogenes serotypes, resistance to desiccation was not statistically different based on mode of growth. These results indicate growth on solid media under aerobic conditions is not always necessary for optimal desiccation survival but may be beneficial when the desiccation resistance of the test serotype is unknown.

scholarly journals Aside Adapte ve Adapte Olmayan Durağan Faz Escherichia coli O157:H7, Salmonella enterica Typhimurium ve Listeria monocytogenes’in Nar Suyundaki Termal Direnci

2019 ◽  
Vol 7 (7) ◽  
pp. 1000
Author(s):  
Zeynal Topalcengiz ◽  
Sefa Işık ◽  
Yusuf Alan
Keyword(s):  
Escherichia Coli ◽  
Thermal Resistance ◽  
Stationary Phase ◽  
Salmonella Enterica ◽  
Thermal Tolerance ◽  
Thermal Inactivation ◽  
Pomegranate Juice ◽  
Escherichia Coli O157 ◽  
Acid Adaptation ◽  
E Coli

The purpose of this study was to investigate the thermal resistance of acid adapted and non-adapted stationary phase Escherichia coli O157:H7, Salmonella enterica Typhimurium and Listeria monocytogenes in pomegranate juice. In addition, the performance of generic E. coli was evaluated as an indicator. Non-adapted stationary phase cells were grown by incubating inoculated tryptic soy broth without glucose (TSB-NG) at 36±1°C for 18±2 hours. Tryptic soy broth with 1% glucose (10 g/l; TSBG) was used for acid adaptation. All media used for L. monocytogenes was supplemented with 0.6% yeast extract. After washing the cells with peptone, 5 ml of pasteurized pomegranate juice was added onto the pellet to obtain inoculated juice with a initial concentration of 107-1010 log CFU/ml. Inoculated pomegranate juice was sealed into the microcapillary tubes. Microtubes were heat treated in waterbaths at 50, 52 and 54±1°C by immersing at pre-determined time intervals. Survived populations were counted on tryptic soy agar (TSA). S. Typhimurium had the lowest thermal resistance in pomegranate juice. At 50°C, E. coli O157:H7 was the most resistant, whereas L. monocytogenes was more thermally tolerant at 52 and 54°C. Acid adaptation decreased the thermal resistance of E. coli O157:H7, but increased the heat resistance of L. monocytogenes at all tested temperatures significantly. Thermal tolerance of S. Typhimurium increased only at 50°C. The most resistant microorganism was non-adapted generic E. coli at 50 and 52°C; acid-adapted L. monocytogenes had the most thermal tolerance at 54°C. Thermal inactivation of microorganisms in pomegranate juice could be tested at lower temperatures compare to other fruit juices. This may be due to the natural antimicrobial effect and more acidic content of pomegranate juice.

scholarly journals ATIVIDADE ANTIMICROBIANA DE MICRORGANISMOS ISOLADOS DE GRÃOS DE KEFIR

2018 ◽  
Vol 19 (0) ◽  
Author(s):  
Priscila Alves Dias ◽  
Daiani Teixeira Silva ◽  
Cláudio Dias Timm
Keyword(s):  
Escherichia Coli ◽  
Staphylococcus Aureus ◽  
Listeria Monocytogenes ◽  
Salmonella Typhimurium ◽  
Salmonella Enterica ◽  
Escherichia Coli O157 ◽  
E Coli

Resumo Kefir é o produto da fermentação do leite pelos grãos de kefir. Esses grãos contêm uma mistura simbiótica de bactérias e leveduras imersas em uma matriz composta de polissacarídeos e proteínas. Muitos benefícios à saúde humana têm sido atribuídos ao kefir, incluindo atividade antimicrobiana contra bactérias Gram positivas e Gram negativas. A atividade antimicrobiana de 60 microrganismos isolados de grãos de kefir, frente à Escherichia coli O157:H7, Salmonella enterica subsp. enterica sorotipos Typhimurium e Enteritidis, Staphylococcus aureus e Listeria monocytogenes, foi estudada através do teste do antagonismo. A ação antimicrobiana dos sobrenadantes das bactérias ácido-lácticas que apresentaram atividade no teste do antagonismo foi testada. O experimento foi repetido usando sobrenadantes com pH neutralizado. Salmonella Typhimurium e Enteritidis sobreviveram por 24 horas no kefir em fermentação. E. coli O157:H7, S. aureus e L. monocytogenes foram recuperados até 72 horas após o início da fermentação. Todos os isolados apresentaram atividade antimicrobiana contra pelo menos um dos patógenos usados no teste do antagonismo. Sobrenadantes de 25 isolados apresentaram atividade inibitória e três mantiveram essa atividade com pH neutralizado. As bactérias patogênicas estudadas sobreviveram por tempo superior àquele normalmente utilizado para a fermentação do kefir artesanal, o que caracteriza perigo em potencial para o consumidor quando a matéria-prima não apresentar segurança sanitária. Lactobacillus isolados de grãos de kefir apresentam atividade antimicrobiana contra cepas de E. coli O157:H7, Salmonella sorotipos Typhimurium e Enteritidis, S. aureus e L. monocytogenes além daquela exercida pela diminuição do pH.

Inactivation of Escherichia coli O157:H7, Salmonella enterica Serotype Enteritidis, and Listeria monocytogenes on Lettuce by Hydrogen Peroxide and Lactic Acid and by Hydrogen Peroxide with Mild Heat

2002 ◽  
Vol 65 (8) ◽  
pp. 1215-1220 ◽  
Author(s):  
CHIA-MIN LIN ◽  
SARAH S. MOON ◽  
MICHAEL P. DOYLE ◽  
KAY H. McWATTERS
Keyword(s):  
Escherichia Coli ◽  
Hydrogen Peroxide ◽  
Lactic Acid ◽  
Listeria Monocytogenes ◽  
Salmonella Enterica ◽  
Salmonella Enteritidis ◽  
Sensory Characteristics ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Log Reduction

Iceberg lettuce is a major component in vegetable salad and has been associated with many outbreaks of foodborne illnesses. In this study, several combinations of lactic acid and hydrogen peroxide were tested to obtain effective antibacterial activity without adverse effects on sensory characteristics. A five-strain mixture of Escherichia coli O157:H7, Salmonella enterica serotype Enteritidis, and Listeria monocytogenes was inoculated separately onto fresh-cut lettuce leaves, which were later treated with 1.5% lactic acid plus 1.5% hydrogen peroxide (H2O2) at 40°C for 15 min, 1.5% lactic acid plus 2% H2O2 at 22°C for 5 min, and 2% H2O2 at 50°C for 60 or 90 s. Control lettuce leaves were treated with deionized water under the same conditions. A 4-log reduction was obtained for lettuce treated with the combinations of lactic acid and H2O2 for E. coli O157:H7 and Salmonella Enteritidis, and a 3-log reduction was obtained for L. monocytogenes. However, the sensory characteristics of lettuce were compromised by these treatments. The treatment of lettuce leaves with 2% H2O2 at 50°C was effective not only in reducing pathogenic bacteria but also in maintaining good sensory quality for up to 15 days. A ≤4-log reduction of E. coli O157:H7 and Salmonella Enteritidis was achieved with the 2% H2O2 treatment, whereas a 3-log reduction of L. monocytogenes was obtained. There was no significant difference (P > 0.05) between pathogen population reductions obtained with 2% H2O2 with 60- and 90-s exposure times. Hydrogen peroxide residue was undetectable (the minimum level of sensitivity was 2 ppm) on lettuce surfaces after the treated lettuce was rinsed with cold water and centrifuged with a salad spinner. Hence, the treatment of lettuce with 2% H2O2 at 50°C for 60 s is effective in initially reducing substantial populations of foodborne pathogens and maintaining high product quality.

Detection of Escherichia coli O157, Salmonella enterica Serovar Typhimurium, and Staphylococcal Enterotoxin B in a Single Sample Using Enzymatic Bio-Nanotransduction

2007 ◽  
Vol 70 (4) ◽  
pp. 841-850 ◽  
Author(s):  
JOSH R. BRANEN ◽  
MARTHA J. HASS ◽  
ERIN R. DOUTHIT ◽  
WUSI C. MAKI ◽  
A. LARRY BRANEN
Keyword(s):  
Escherichia Coli ◽  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Staphylococcal Enterotoxin B ◽  
Escherichia Coli O157 ◽  
Dna Templates ◽  
E Coli ◽  
Serovar Typhimurium ◽  
Biological Recognition ◽  
Enterotoxin B

Enzymatic bio-nanotransduction is a biological detection scheme based on the production of nucleic acid nano-signals (RNA) in response to specific biological recognition events. In this study, we applied an enzymatic bio-nanotransduction system to the detection of important food-related pathogens and a toxin. Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium, and staphylococcal enterotoxin B (SEB) were chosen because of the implications of these targets to food safety. Primary antibodies to each of the targets were used to functionalize magnetic beads and produce biological recognition elements (antibodies) conjugated to nano-signal–producing DNA templates. Immunomagnetic capture that was followed by in vitro transcription of DNA templates bound to target molecules produced RNA nano-signals specific for every target in the sample. Discrimination of RNA nano-signals with a standard enzyme-linked oligonucleotide fluorescence assay provided a correlation between nano-signal profiles and target concentrations. The estimated limit of detection was 2.4 × 103 CFU/ml for E. coli O157:H7, 1.9 × 104 CFU/ml for S. enterica serovar Typhimurium, and 0.11 ng/ml for SEB with multianalyte detection in buffer. Low levels of one target were also detected in the presence of interference from high levels of the other targets. Finally, targets were detected in milk, and detection was improved for E. coli O157 by heat treatment of the milk.

scholarly journals Effects of Acid Adaptation, Product pH, and Heating on Survival of Escherichia coli O157:H7 in Pepperoni

2000 ◽  
Vol 66 (4) ◽  
pp. 1726-1729 ◽  
Author(s):  
Denise C. R. Riordan ◽  
Geraldine Duffy ◽  
James J. Sheridan ◽  
Richard C. Whiting ◽  
Ian S. Blair ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Thermal Inactivation ◽  
Escherichia Coli O157 ◽  
Acid Adaptation ◽  
E Coli

ABSTRACT The thermotolerance of E. coli O157:H7 cells (strain 380-94) heated in pepperoni is reported. Information on the pattern of thermal inactivation of E. coli O157:H7 in pepperoni was applied in the development of heating processes designed to reduceE. coli O157:H7 numbers therein by 5 log10units.

Determination of 5-Log Reduction Times for Escherichia coli O157:H7, Salmonella enterica, or Listeria monocytogenes in Acidified Foods with pH 3.5 or 3.8†

2013 ◽  
Vol 76 (7) ◽  
pp. 1245-1249 ◽  
Author(s):  
F. BREIDT ◽  
K. KAY ◽  
J. COOK ◽  
J. OSBORNE ◽  
B. INGHAM ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Acetic Acid ◽  
Listeria Monocytogenes ◽  
Benzoic Acid ◽  
Salmonella Enterica ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Log Reduction ◽  
Acidified Foods

A critical factor in ensuring the safety of acidified foods is the establishment of a thermal process that assures the destruction of acid-resistant vegetative pathogenic and spoilage bacteria. For acidified foods such as dressings and mayonnaises with pH values of 3.5 or higher, the high water phase acidity (acetic acid of 1.5 to 2.5% or higher) can contribute to lethality, but there is a lack of data showing how the use of common ingredients such as acetic acid and preservatives, alone or in combination, can result in a 5-log reduction for strains of Escherichia coli O157:H7, Salmonella enterica, and Listeria monocytogenes in the absence of a postpackaging pasteurization step. In this study, we determined the times needed at 10°C to achieve a 5-log reduction of E. coli O157:H7, S. enterica, and L. monocytogenes in pickling brines with a variety of acetic and benzoic acid combinations at pH 3.5 and 3.8. Evaluation of 15 different acid-pH combinations confirmed that strains of E. coli O157:H7 were significantly more acid resistant than strains of S. enterica and L. monocytogenes. Among the acid conditions tested, holding times of 4 days or less could achieve a 5-log reduction for vegetative pathogens at pH 3.5 with 2.5% acetic acid or at pH 3.8 with 2.5% acetic acid containing 0.1% benzoic acid. These data indicate the efficacy of benzoic acid for reducing the time necessary to achieve a 5-log reduction in target pathogens and may be useful for supporting process filings and the determination of critical controls for the manufacture of acidified foods.

Effectiveness and Functional Mechanism of a Multicomponent Sanitizer against Biofilms Formed by Escherichia coli O157:H7 and Five Salmonella Serotypes Prevalent in the Meat Industry

2020 ◽  
Vol 83 (4) ◽  
pp. 568-575
Author(s):  
RONG WANG ◽  
YOU ZHOU ◽  
NORASAK KALCHAYANAND ◽  
DAYNA M. HARHAY ◽  
TOMMY L. WHEELER
Keyword(s):  
Escherichia Coli ◽  
Salmonella Enterica ◽  
Three Dimensional ◽  
Short Exposure ◽  
Escherichia Coli O157 ◽  
Bacterial Cells ◽  
Meat Processing ◽  
E Coli ◽  
Biofilm Removal ◽  
Biofilm Structure

ABSTRACT Biofilm formation by Escherichia coli O157:H7 and Salmonella enterica at meat processing plants poses a potential risk of meat product contamination. Many common sanitizers are unable to completely eradicate biofilms formed by these foodborne pathogens because of the three-dimensional biofilm structure and the presence of bacterial extracellular polymeric substances (EPSs). A novel multifaceted approach combining multiple chemical reagents with various functional mechanisms was used to enhance the effectiveness of biofilm control. We tested a multicomponent sanitizer consisting of a quaternary ammonium compound (QAC), hydrogen peroxide, and the accelerator diacetin for its effectiveness in inactivating and removing Escherichia coli O157:H7 and Salmonella enterica biofilms under meat processing conditions. E. coli O157:H7 and Salmonella biofilms on common contact surfaces were treated with 10, 20, or 100% concentrations of the multicomponent sanitizer solution for 10 min, 1 h, or 6 h, and log reductions in biofilm mass were measured. Scanning electron microscopy (SEM) was used to directly observe the effect of sanitizer treatment on biofilm removal and bacterial morphology. After treatment with the multicomponent sanitizer, viable E. coli O157:H7 and Salmonella biofilm cells were below the limit of detection, and the prevalence of both pathogens was low. After treatment with a QAC-based control sanitizer, surviving bacterial cells were countable, and pathogen prevalence was higher. SEM analysis of water-treated control samples revealed the three-dimensional biofilm structure with a strong EPS matrix connecting bacteria and the contact surface. Treatment with 20% multicomponent sanitizer for 10 min significantly reduced biofilm mass and weakened the EPS connection. The majority of the bacterial cells had altered morphology and compromised membrane integrity. Treatment with 100% multicomponent sanitizer for 10 min dissolved the EPS matrix, and no intact biofilm structure was observed; instead, scattered clusters of bacterial aggregates were detected, indicating the loss of cell viability and biofilm removal. These results indicate that the multicomponent sanitizer is effective, even after short exposure with dilute concentrations, against E. coli O157:H7 and S. enterica biofilms. HIGHLIGHTS

Acid Tolerance of Acid-Adapted and Nonadapted Escherichia coli O157:H7 following Habituation (10°C) in Fresh Beef Decontamination Runoff Fluids of Different pH Values

2004 ◽  
Vol 67 (4) ◽  
pp. 638-645 ◽  
Author(s):  
JOHN SAMELIS ◽  
PATRICIA KENDALL ◽  
GARY C. SMITH ◽  
JOHN N. SOFOS
Keyword(s):  
Escherichia Coli ◽  
Acid Tolerance ◽  
Growth Potential ◽  
Escherichia Coli O157 ◽  
Sterile Water ◽  
Water Control ◽  
Term Survival ◽  
Acid Adaptation ◽  
E Coli ◽  
Natural Flora

This study evaluated survival of Escherichia coli O157:H7 strain ATCC 43895 during exposure to pH 3.5 following its habituation for 2 or 7 days at 10°C in fresh beef decontamination waste runoff fluid mixtures (washings) containing 0, 0.02, or 0.2% of lactic or acetic acids. Meat washings and sterile water (control) were initially inoculated with approximately 5 log CFU/ml of acid- and nonadapted E. coli O157:H7 cells cultured (30°C, 24 h) in broth with and without 1% glucose, respectively. After 2 days, E. coli O157:H7 survivors from acetate washings (pH 3.7 to 4.7) survived at pH 3.5 better than E. coli O157:H7 survivors from lactate washings (pH 3.1 to 4.6), especially when the original inoculum was acid adapted. Also, although E. coli O157:H7 habituated in sterile water for 2 days survived well at pH 3.5, the corresponding survivors from nonacid water meat washings (pH 6.8) were rapidly killed at pH 3.5, irrespective of acid adaptation. After 7 days, E. coli O157:H7 survivors from acetate washings (pH 3.6 to 4.7) continued to resist pH 3.5, whereas those from lactate washings died off. This loss of acid tolerance by E. coli O157:H7 was due to either its low survival in 0.2% lactate washings (pH 3.1) or its acid sensitization in 0.02% lactate washings, in which a Pseudomonas-like natural flora showed extensive growth (>8 log CFU/ml) and the pH increased to 6.5 to 6.6. Acid-adapted E. coli O157:H7 populations habituated in water washings (pH 7.1 to 7.3) for 7 days continued to be acid sensitive, whereas nonadapted populations increased their acid tolerance, a response merely correlated with their slight (<1 log) growth at 10°C. These results indicate that the expression of high acid tolerance by acid-adapted E. coli O157:H7 can be maintained or enhanced in acid-diluted meat decontamination waste runoff fluids of pH levels that could permit long-term survival at 10°C. Previous acid adaptation, however, could reduce the growth potential of E. coli O157:H7 at 10°C in nonacid waste fluids of high pH and enriched in natural flora. These conditions might further induce an acid sensitization to stationary E. coli O157:H7 cells.

scholarly journals Detection of Escherichia coli O157:H7 and Salmonella enterica in Air and Droplets at Three U.S. Commercial Beef Processing Plants†

2012 ◽  
Vol 75 (12) ◽  
pp. 2213-2218 ◽  
Author(s):  
JOHN W. SCHMIDT ◽  
TERRANCE M. ARTHUR ◽  
JOSEPH M. BOSILEVAC ◽  
NORASAK KALCHAYANAND ◽  
TOMMY L. WHEELER
Keyword(s):  
Escherichia Coli ◽  
Salmonella Enterica ◽  
Published Data ◽  
Escherichia Coli O157 ◽  
Liquid Droplets ◽  
Air Samples ◽  
E Coli ◽  
Beef Processing ◽  
Processing Plants ◽  
Plate Counts

Bacteria are known to be present in the air at beef processing plants, but published data regarding the prevalences of airborne Escherichia coli O157:H7 and Salmonella enterica are very limited. To determine if airborne pathogens were present in beef processing facilities, we placed sedimentation sponges at various locations in three commercial beef plants that processed cattle from slaughter through fabrication. For the 291 slaughter area air samples, E. coli O157:H7 was isolated from 15.8% and S. enterica from 16.5%. Of the 113 evisceration area air samples, E. coli O157:H7 was isolated from only one sample and S. enterica was not isolated from any sample. Pathogens were not isolated from any of the 87 air samples from fabrication areas. Pathogen prevalences, aerobic plate counts, and Enterobacteriaceae counts were highest for air samples obtained from locations near hide removal operations. The process of hide removal disperses liquid droplets, which may contact neighboring carcasses. Samples were obtained both from hide removal locations that were close enough to hide pullers to be contacted by droplets and from locations that were not contacted by droplets. Higher pathogen prevalences, aerobic plate counts, and Enterobacteriaceae counts were observed at locations with samples contacted by the hide removal droplets. We conclude that the hide removal processes likely introduce pathogens into the air via a dispersion of liquid droplets and that these droplets may be an underappreciated source of hide-to-carcass contamination.

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