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1.
Int J Food Microbiol ; 321: 108560, 2020 May 16.
Artículo en Inglés | MEDLINE | ID: mdl-32078866

RESUMEN

Foodborne illnesses affect the health of consumers worldwide, and thus searching for potential antimicrobial agents against foodborne pathogens is given an increased focus. This research evaluated the influence of sodium lactate (SL), encapsulated (e) and unencapsulated (u) polyphosphates (PP; sodium tripolyphosphate, STP; sodium acid pyrophosphate, SPP), and their combinations on Salmonella Typhimurium, Escherichia coli O157:H7 and Staphylococcus aureus growth in cooked ground beef during 30 day storage at 4 or 10 °C. pH, water activity (aw), oxidation-reduction potential (ORP) and S. Typhimurium, E. coli O157:H7 and S. aureus counts were determined. S. Typhimurium was not found in SPP-SL combination groups after 30 day storage at 4 °C (P <0.05). Lower S. Typhimurium levels were determined in only SL containing groups stored at 10 °C than group with only tested microorganism (MO, P < 0.05). Although there was no change in S. Typhimurium load in all SL incorporated groups during 10 °C storage, S. Typhimurium count increased in other groups (P < 0.05). E. coli O157:H7 in MO and STP groups showed an increase at 4 °C, whereas it decreased in SPP-SL combination groups (P < 0.05). A gradual increase in E. coli O157:H7 at 10 °C was determined in MO and only PP incorporated groups, whereas there was a decrease in STP-SL or SPP-SL combination groups (P < 0.05). E. coli O157:H7 count was stable in SL containing groups during 10 °C storage. A gradual decrease in S. aureus was determined in all treatments at 4 °C, whereas S. aureus count increased in MO and uSTP groups during 10 °C storage (P < 0.05). There was no change in S. aureus level in only eSTP or uSPP or ueSTP containing groups at 10 °C, meantime it decreased in other groups (P < 0.05). The lowest S. aureus load was achieved by uSPP-SL or eSPP-SL or ueSPP-SL combinations after 30 days at both storage temperatures (P < 0.05). In general, pH was higher in samples with STP than those with SPP and control (P < 0.05). The lowest aw was generally obtained in all SL containing groups at both storage temperatures (P < 0.05). Lower ORP was determined in all PP incorporated groups during storage at both temperatures compared to others (P < 0.05). ORP in all treatments generally increased (P < 0.05) during storage at both storage temperatures. This study showed that encapsulation is not a factor affecting antimicrobial efficiency of PP and using PP-SL combinations have synergistic effect on reducing the viability of S. Typhimurium, E. coli O157:H7 and S. aureus and their subsequent growth ability in cooked ground beef.


Asunto(s)
Escherichia coli O157/efectos de los fármacos , Polifosfatos/farmacología , Carne Roja/microbiología , Salmonella typhimurium/efectos de los fármacos , Lactato de Sodio/farmacología , Staphylococcus aureus/efectos de los fármacos , Animales , Cápsulas , Bovinos , Recuento de Colonia Microbiana , Sinergismo Farmacológico , Escherichia coli O157/crecimiento & desarrollo , Manipulación de Alimentos , Microbiología de Alimentos , Polifosfatos/química , Carne Roja/análisis , Salmonella typhimurium/crecimiento & desarrollo , Staphylococcus aureus/crecimiento & desarrollo , Temperatura
2.
Food Microbiol ; 87: 103382, 2020 May.
Artículo en Inglés | MEDLINE | ID: mdl-31948623

RESUMEN

Although due to their acidity some fruit juices are considered safe, several outbreaks have been reported. For processing fruit juices, microwave heating offers advantages such as shorter come-up time, faster and uniform heating, and energy efficiency. Thus, it could be a beneficial alternative to conventional pasteurization. The objective of this study was to study the inactivation kinetics of Escherichia coli O157:H7 and Salmonella Typhimurium under microwave pasteurization at temperatures between 80 and 90 °C, i.e., at conditions that are employed in conventional pasteurization. Inoculated juices were treated at different power levels (600 W, 720 W) and treatment times (5s, 10s, 15s, 20s, 25s). Time-temperature profiles were obtained by fiber-optic sensors in contact with the samples allowing continuous data collection. The log-logistic and Arrhenius equations were used to account for the influence of the temperature history; thus, resulting in two different modeling approaches that were compared in terms of their prediction abilities. Survival kinetics including non-isothermal conditions were described by a non-linear ordinary differential equation that was numerically solved by the Runge-Kutta method (ode45 in MATLAB ®). The lsqcurvefit function (MATLAB®) was employed to estimate the corresponding survival parameters, which were obtained from freshly made apple juice, whereas the prediction ability of these parameters was evaluated on commercial apple juices. Results indicated that inactivation increased with power level, temperature, and treatment time reaching a microbial reduction up to 7 Log10 cycles. The study is relevant to the food industry because it provides a quantitative tool to predict survival characteristics of pathogens at other non-isothermal processing conditions.


Asunto(s)
Escherichia coli O157/efectos de la radiación , Irradiación de Alimentos/métodos , Jugos de Frutas y Vegetales/microbiología , Malus/microbiología , Salmonella typhimurium/efectos de la radiación , Recuento de Colonia Microbiana , Escherichia coli O157/crecimiento & desarrollo , Irradiación de Alimentos/instrumentación , Microondas , Salmonella typhimurium/crecimiento & desarrollo , Temperatura
3.
Food Microbiol ; 87: 103387, 2020 May.
Artículo en Inglés | MEDLINE | ID: mdl-31948628

RESUMEN

We evaluated the bactericidal efficacy of the simultaneous application of ultraviolet-A (UV-A) irradiation and fumaric acid (FA) against Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium, and Listeria monocytogenes in apple juice and as well as investigated the effects of this treatment on product quality. Further, we elucidated the mechanisms underlying their synergistic bactericidal action. Simultaneous UV-A light irradiation and 0.1% FA treatment for 30 min resulted in 6.65-, 6.27-, and 6.49-log CFU/ml reductions in E. coli O157:H7, S. Typhimurium, and L. monocytogenes, respectively, which involved 3.15, 2.21, and 3.43 log CFU reductions, respectively, and these were attributed to the synergistic action of the combined treatments. Mechanistic investigations suggested that the combined UVA-FA treatment resulted in significantly greater bacterial cell membrane damage and intracellular reactive oxygen species (ROS) generation. UVA-FA treatment for 30 min did not cause significant changes to the color, nonenzymatic browning index, pH, and total phenolic content of apple juice. These results suggest that combined UVA-FA treatment can be effectively used to control foodborne pathogens in apple juice without affecting its quality.


Asunto(s)
Antibacterianos/farmacología , Conservación de Alimentos/métodos , Jugos de Frutas y Vegetales/microbiología , Fumaratos/farmacología , Malus/microbiología , Escherichia coli O157/efectos de los fármacos , Escherichia coli O157/crecimiento & desarrollo , Escherichia coli O157/metabolismo , Escherichia coli O157/efectos de la radiación , Conservación de Alimentos/instrumentación , Jugos de Frutas y Vegetales/análisis , Listeria monocytogenes/efectos de los fármacos , Listeria monocytogenes/crecimiento & desarrollo , Listeria monocytogenes/metabolismo , Listeria monocytogenes/efectos de la radiación , Viabilidad Microbiana/efectos de los fármacos , Viabilidad Microbiana/efectos de la radiación , Especies Reactivas de Oxígeno/metabolismo , Salmonella typhimurium/efectos de los fármacos , Salmonella typhimurium/crecimiento & desarrollo , Salmonella typhimurium/metabolismo , Salmonella typhimurium/efectos de la radiación , Rayos Ultravioleta
4.
Food Microbiol ; 87: 103388, 2020 May.
Artículo en Inglés | MEDLINE | ID: mdl-31948629

RESUMEN

The growing demand for minimally processed foods with clean labels has stimulated research into mild processing methods and natural antimicrobials to replace intensive heating and conventional preservatives, respectively. However, we have previously demonstrated that repetitive exposure of some bacteria to mild heat or subinhibitory concentrations of essential oil constituents (EOCs) may induce the emergence of mutants with increased resistance to these treatments. Since the combination of mild heat with some EOCs has a synergistic effect on microbial inactivation, we evaluated the potential of such combinations against our resistant E. coli mutants. While citral, carvacrol and t-cinnamaldehyde synergistically increased heat inactivation (53.0 °C, 10 min) of the wild-type MG1655 suspended in buffer, only the combination with carvacrol (200 µl/l) was able to mitigate the increased resistance of all the mutants. Moreover, the combination of heat and carvacrol acted synergistically inactivating heat-resistant variants of E. coli O157:H7 (ATCC 43888). This combined treatment could synergistically achieve more than 5 log10 reductions of the most resistant mutants in coconut water, although the temperature had to be raised to 57.0 °C. Therefore, the combination of mild heat with carvacrol appears to hold promise for mild processing, and it is expected to counteract the development of heat resistance.


Asunto(s)
Antibacterianos/farmacología , Cocos/química , Escherichia coli O157/efectos de los fármacos , Aceites Volátiles/farmacología , Extractos Vegetales/farmacología , Aceites Vegetales/farmacología , Acroleína/análogos & derivados , Acroleína/farmacología , Monoterpenos Acíclicos/farmacología , Cimenos/farmacología , Farmacorresistencia Bacteriana , Escherichia coli O157/crecimiento & desarrollo , Calor
5.
J Agric Food Chem ; 68(8): 2357-2365, 2020 Feb 26.
Artículo en Inglés | MEDLINE | ID: mdl-31967810

RESUMEN

Here, we investigated the effect of cold plasma (CP) on the biological activities of phloroglucinol. Phloroglucinol (7.92 and 15.84 mM in methanol) was treated with air dielectric barrier discharge plasma at 250 W. In vitro, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity and ferrous-reducing antioxidant power (FRAP) values of phloroglucinol increased in plasma treatment in a time-dependent manner. CP treatment of phloroglucinol decreased the lipid oxidation of oil emulsion during storage and increased the antimicrobial activity against Bacillus cereus, Escherichia coli O157:H7, and Staphylococcus aureus. Angiotensin-converting enzyme (ACE) inhibitory activity of phloroglucinol increased and total phenolic content decreased based on CP treatment. The CP-induced polymerization of phloroglocinol to phlorotannin derivatives was identified using high-performance liquid chromatography with UV detector and electrospray ionization/mass spectrometry (HPLC-UV-ESI/MS) method. Consequently, the polymer structure of phloroglucinol was found in the CP-treated phloroglucinol. In addition, CP enhances the biological activity of phloroglucinol and could be applied to bioactive materials in food and related industries.


Asunto(s)
Floroglucinol/química , Floroglucinol/farmacología , Gases em Plasma/química , Antibacterianos/química , Antibacterianos/farmacología , Antioxidantes/química , Antioxidantes/farmacología , Bacillus cereus/efectos de los fármacos , Bacillus cereus/crecimiento & desarrollo , Escherichia coli O157/efectos de los fármacos , Escherichia coli O157/crecimiento & desarrollo , Polimerizacion , Staphylococcus aureus/efectos de los fármacos , Staphylococcus aureus/crecimiento & desarrollo
6.
Int J Food Microbiol ; 316: 108423, 2020 Mar 02.
Artículo en Inglés | MEDLINE | ID: mdl-31722269

RESUMEN

This study aimed to evaluate growth behaviour of Escherichia coli O157:H7, Salmonella spp., and background microbiota in ground lean camel meat during refrigerated storage for up to 7 d, and determine thermal inactivation parameters (D and z-values) of the pathogens in the meat. Fresh ground camel meat samples were individually inoculated with two isolates of each E. coli O157:H7 strains and Salmonella serovars. Inoculated and uninoculated samples were stored aerobically at 4 °C and abusive temperature (10 °C) for 1, 4 and 7 d. Inoculated samples were also heat-treated in a circulating water bath at 55-65 °C. Upon storage for 7 d at 4 °C, the population of E. coli O157:H7 and Salmonella cells decreased significantly in samples. In contrast, samples stored at 10 °C showed significant increases in microbial populations. With storage, the populations of mesophilic lactic acid bacteria, mesophilic total plate counts, yeasts and molds, Pseudomonas spp., as well as Enterobacteriaceae increased significantly. E. coli O157:H7 strains showed average D-values at 57.5 to 65 °C ranging from 1.8 to 0.067 min while Salmonella spp. at 55 to 62.5 °C showed D-values ranging from 2.2 to 0.057 min. The z-values of E. coli O157:H7 strains were 4.6 and 5.0 °C and were 5.1 and 5.5 °C for Salmonella spp. This study provides information to assist food industry and retail meat processors to enhance safety and storage quality of camel meat and facilitate validation of thermal processing of camel meat products.


Asunto(s)
Escherichia coli O157/crecimiento & desarrollo , Microbiología de Alimentos , Productos de la Carne/microbiología , Pasteurización/métodos , Salmonella/crecimiento & desarrollo , Animales , Camelus , Recuento de Colonia Microbiana , Industria de Procesamiento de Alimentos , Temperatura
7.
J Appl Microbiol ; 128(1): 301-309, 2020 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-31541508

RESUMEN

AIMS: The aim of this study was to evaluate the microbiological quality of commercially prepared ready-to-eat (RTE) sushi by enumerating aerobic mesophilic bacteria (AMB) and thermotolerant coliforms (TC) and detecting Escherichia coli and Salmonella ssp. An isolate was identified as E. coli O157:H7 which was evaluated for its virulence and antimicrobial resistance profiling as well as its ability to form biofilms on stainless steel. METHODS AND RESULTS: There were four sampling events in seven establishments, totalling 28 pools of sushi samples. Mean AMB counts ranged between 5·2 and 7·7 log CFU per gram. The enumeration of TC varied between 2·1 and 2·7 log MPN per gram. Salmonella ssp. were not detected, and one sample was positive for E. coli and was identified as E. coli O157:H7. To the best of our knowledge, this is the first report of E. coli O157:H7 in sushi samples in the world literature. This isolate presented virulence genes stx1, stx2, eae and hlyA. It was also susceptible to 14 antimicrobials tested and had the ability to form biofilms on stainless steel. CONCLUSIONS: There is a need to improve the good hygiene practices adopted in establishments selling sushi in the city of Pelotas, Brazil. In addition, the isolated E. coli O157:H7 carries a range of important virulence genes being a potential risk to consumer health, as sushi is a RTE food. This isolate also presents biofilm formation ability, therefore, may trigger a constant source of contamination in the production line of this food. SIGNIFICANCE AND IMPACT OF THE STUDY: The increase in the consumption of sushi worldwide attracts attention regarding the microbiological point of view, since it is a ready-to-eat food. To our knowledge, this was the first time that E. coli O157:H7 was identified in sushi samples.


Asunto(s)
Escherichia coli O157/aislamiento & purificación , Microbiología de Alimentos , Alimentos Marinos/microbiología , Animales , Antibacterianos/farmacología , Biopelículas/crecimiento & desarrollo , Brasil , Recuento de Colonia Microbiana , Escherichia coli O157/efectos de los fármacos , Escherichia coli O157/genética , Escherichia coli O157/crecimiento & desarrollo , Pruebas de Sensibilidad Microbiana , Acero Inoxidable , Termotolerancia , Virulencia/genética
8.
Int J Food Microbiol ; 313: 108381, 2020 Jan 16.
Artículo en Inglés | MEDLINE | ID: mdl-31670167

RESUMEN

As a raw agricultural commodity, wheat is exposed to microbial contamination; therefore, enteric pathogens may be among its microbiota creating a food safety risk in milled products. This research evaluates (1) the effectiveness of organic acids dissolved in saline solutions to reduce the counts of pathogenic microorganisms in soft and hard wheat, and also investigates the effect of seasonal temperature on (2) survivability of pathogens in wheat kernels and on (3) pathogen inactivation during tempering with saline organic acid solutions. Wheat samples were inoculated with cocktails of either 5 serovars of Salmonella enterica, 5 E. coli O157:H7 or 6 non-O157 Shiga toxin-producing E. coli (STEC) strains to achieve a concentration of ~7 log CFU/g. Inoculated samples were allowed to stand for 7-days at temperatures (2.0, 10.8, 24.2, 32 °C) corresponding to those experienced during winter, spring/fall, and summer (average and maximum) in the main wheat growing regions in the state of Nebraska, USA. Besides water, solutions containing acid (acetic or lactic 2.5% or 5.0% v/v) and NaCl (~26% w/v) were used for tempering the wheat to 15.0% (soft) and 15.5% (hard) moisture at the different seasonal temperatures. The survival of pathogenic microorganisms throughout the resting period, and before and after tempering was analyzed by plating samples on injury-recovery media. The survival rate of pathogenic microorganisms on wheat kernels was higher at temperatures experienced during the winter (2.0 °C) and spring/fall (10.8 °C) months. Regardless of tempering temperature, the initial pathogen load was reduced significantly by all solutions when compared to the control tempered with water (P ≤ .05). The combination of lactic acid (5.0%) and NaCl was the most effective treatment against Salmonella enterica, E. coli O157:H7 and non-O157 STEC, with average reduction values of 1.8, 1.8 and 1.6 log CFU/g for soft wheat and 2.6, 2.4 and 2.4 log CFU/g for hard wheat, respectively. Implementation of organic acids and NaCl in tempering water may have the potential to reduce the risk of pathogen contamination in milled products.


Asunto(s)
Ácidos/farmacología , Manipulación de Alimentos/métodos , Cloruro de Sodio/farmacología , Triticum/microbiología , Ácidos/química , Recuento de Colonia Microbiana , Escherichia coli O157/efectos de los fármacos , Escherichia coli O157/crecimiento & desarrollo , Manipulación de Alimentos/instrumentación , Microbiología de Alimentos , Inocuidad de los Alimentos , Salmonella enterica/efectos de los fármacos , Salmonella enterica/crecimiento & desarrollo , Estaciones del Año , Temperatura
9.
Food Microbiol ; 85: 103274, 2020 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-31500714

RESUMEN

The impact of plant development, environmental conditions at the time of inoculation, and inoculum concentration on survival of attenuated BSL1 Escherichia coli O157:H7 strain ATCC 700728 on field-grown romaine lettuce was evaluated over 3 years. E. coli 700728 was inoculated onto 4- and 6-week-old romaine lettuce plants in the Salinas Valley, CA, at night or the next morning with either low (5 log) or high (7 log) cell numbers per plant to simulate a single aqueous contamination event. At night, when leaf wetness and humidity levels were high, E. coli cell numbers declined by 0.5 log CFU/plant over the first 8-10 h. When applied in the morning, E. coli populations declined up to 2 log CFU/plant within 2 h. However, similar numbers of E. coli were retrieved from lettuce plants at 2 and 7 days. E. coli cell numbers per plant were significantly lower (P < 0.05) 7 days after application onto 4-week-old compared to 6-week-old plants. E. coli 700728 could be recovered by plating or enrichment from a greater proportion of plants for longer times when inoculated at high compared with low initial concentrations and after inoculation of 6-week-old plants compared with 4-week-old plants, even at the low initial inoculum. A contamination event near harvest or when leaf wetness and humidity levels are high may enhance survivability, even when low numbers of E. coli are introduced.


Asunto(s)
Escherichia coli O157/crecimiento & desarrollo , Lechuga/microbiología , Viabilidad Microbiana , Hojas de la Planta/microbiología , Recuento de Colonia Microbiana , Seguridad de Productos para el Consumidor , Microbiología de Alimentos , Humedad , Factores de Tiempo
10.
Food Microbiol ; 86: 103327, 2020 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-31703855

RESUMEN

The study investigated the efficacy of two GRAS-status phytochemicals, mega-resveratrol (RV) and naringenin (NG) to inactivate Escherichia coli O157:H7 (EHEC) in apple cider. A five-strain mixture of EHEC (∼7 log CFU/ml) was inoculated into cider, followed by the addition of RV (8.7 mM and 13.0 mM) or NG (7.3 mM and 11.0 mM). The cider samples were stored at 4 °C for 14 days and EHEC was enumerated on days 0,1,5,7 and 14. The deleterious effects of RV and NG on EHEC cells were visualized by scanning electron microscopy (SEM), and RT-qPCR was done to determine the effect of phytochemicals on three known acid resistance (AR) systems of EHEC. NG was more effective than RV and reduced EHEC counts by ∼4.5 log CFU/ml by day 14, whereas RV reduced counts by ∼2.5 log CFU/ml compared to controls (P < 0.05). SEM showed that RV and NG resulted in the destruction of EHEC cells, and surviving bacteria appeared 'lemon shaped'. RT-qPCR results revealed that RV and NG downregulated the transcription of AR associated genes in EHEC (P < 0.05). Results suggest the potential use of RV and NG as natural antimicrobial additives to enhance the microbiological safety of apple cider. However, sensory analysis studies are warranted.


Asunto(s)
Escherichia coli O157/efectos de los fármacos , Flavanonas/farmacología , Aditivos Alimentarios/farmacología , Conservación de Alimentos/métodos , Jugos de Frutas y Vegetales/microbiología , Malus/microbiología , Resveratrol/farmacología , Escherichia coli O157/crecimiento & desarrollo , Malus/química , Viabilidad Microbiana/efectos de los fármacos
11.
Food Microbiol ; 86: 103348, 2020 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-31703879

RESUMEN

The effects of the incorporation of the essential oils from Origanum vulgare L. (OVEO; 0.07 µL/g) and Rosmarinus officinalis L. (ROEO; 2.65 µL/g) in combination in Minas Frescal cheese on the counts of the probiotic Lactobacillus acidophilus LA-5 and Escherichia coli O157:H7 were evaluated during refrigerated storage (7 ±â€¯0.5 °C). The terpenes of OVEO and ROEO, survival of the probiotic strain during in vitro digestion, as well as the physicochemical and sensory aspects were also monitored in Minas Frescal cheese. All terpenes decreased in cheese when the storage time increased. The incorporation of OVEO and ROEO delayed the increase in L. acidophilus LA-5 counts in cheese, but did not affect its ability to survive in cheese under simulated gastrointestinal conditions. The decreases in counts of E. coli O157:H7 observed in the first 15 days of refrigerated storage were strongly correlated (r ≥ 0.82) with the terpenes detected in cheese. Scores attributed for aroma, flavor, overall impression and purchase intention of cheese with OVEO and ROEO increased with the increase of the storage time. The incorporation of OVEO and ROEO in combination could be a strategy to control E. coli O157:H7 in probiotic Minas cheese during storage; however, the amounts of these substances should be cautiously selected considering possible negative sensory impacts in this product.


Asunto(s)
Queso/microbiología , Escherichia coli O157/crecimiento & desarrollo , Aditivos Alimentarios/análisis , Lactobacillus acidophilus/crecimiento & desarrollo , Aceites Volátiles/análisis , Origanum/química , Aceites Vegetales/análisis , Rosmarinus/química , Queso/análisis , Escherichia coli O157/efectos de los fármacos , Aditivos Alimentarios/farmacología , Humanos , Lactobacillus acidophilus/efectos de los fármacos , Viabilidad Microbiana/efectos de los fármacos , Aceites Volátiles/farmacología , Aceites Vegetales/farmacología , Gusto
12.
J Food Sci ; 84(11): 3241-3245, 2019 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-31604365

RESUMEN

Escherichia coli O157:H7 is an important foodborne pathogen and has been implicated in numerous food poisoning outbreaks worldwide. Although several microbiological and molecular methods have been developed to detect E. coli O157:H7, the difficulty to rapidly detect low levels of the foodborne bacteria persists. Here, the optimization of a filtration technique to concentrate and rapidly detect E. coli O157:H7 was conducted. Using homogenates prepared from freshly cut lettuce and cabbage samples, the E. coli O157:H7 concentration efficiencies of seven membrane filters were compared. Mixed cellulose ester (MCE) and polyvinylidene difluoride (PVDF) filters demonstrated the highest bacterial recoveries. In addition, the optimal E. coli O157:H7 detachment method from MCE filters after filtration was investigated. Tapping for 80 s was demonstrated to be the most effective method for detaching bacteria from the filters. Further, the possibility of the rapid detection of low levels of E. coli O157:H7 in lettuce and cabbage was evaluated using real-time polymerase chain reaction after bacterial concentration using MCE and PVDF filters. The use of MCE filters enabled the detection of 10° CFU/g (5 CFU/g) of E. coli O157:H7 within 2 hr without microbial enrichment culture. Therefore, concentration by filtration can be used for the rapid detection of low levels of foodborne pathogens. PRACTICAL APPLICATION: The modified method, which has been verified in this study, has been optimized to reduce the analysis time and to detect very low concentrations of E. coli O157:H7 within 2 hr. All these detection systems have a direct economic impact on the food analysis of producers, health authorities, or third-party laboratories.


Asunto(s)
Escherichia coli O157/aislamiento & purificación , Filtración/métodos , Reacción en Cadena en Tiempo Real de la Polimerasa/métodos , Brassica/microbiología , Recuento de Colonia Microbiana , Escherichia coli O157/genética , Escherichia coli O157/crecimiento & desarrollo , Contaminación de Alimentos/análisis , Microbiología de Alimentos , Lechuga/microbiología
13.
J Microbiol Biotechnol ; 29(12): 1975-1981, 2019 Dec 28.
Artículo en Inglés | MEDLINE | ID: mdl-31601061

RESUMEN

Recently, outbreaks of food-borne diseases linked to fresh produce have been an emerging public health concerns worldwide. Previous research has shown that when human pathogens co-exist with plant pathogens, they have improved growth and survival rates. In this study, we have assessed whether Escherichia coli O157:H7 benefits in the existence of a phytopathogenic bacterium and the underlying mechanisms were further investigated. When Pseudomonas syringae pv. tomato DC3000 (Pst DC3000) and E. coli O157:H7 were co-inoculated by either dipping or infiltration methods, the populations of E. coli O157:H7 increased; however, no effect was observed when type three secretion system (T3SS) mutants were used instead, suggesting that E. coli O157:H7 benefits from the presence of Pst DC3000. In addition, this study confirmed that the E. coli O157:H7 populations increased when they occupied the tomato leaf intercellular space; this colonization of the interior of the leaves was possible due to the suppression of the PAMP triggered immunity (PTI) by Pst DC3000, in particular with the AvrPto effector. In conclusion, our data supports a plausible model that E. coli O157:H7 benefits from the presence of Pst DC3000 via AvrPto suppression of the PTI resistance.


Asunto(s)
Escherichia coli O157/crecimiento & desarrollo , Lycopersicon esculentum/microbiología , Pseudomonas syringae/crecimiento & desarrollo , Proteínas Bacterianas/genética , Técnicas de Cocultivo , Recuento de Colonia Microbiana , Escherichia coli O157/genética , Contaminación de Alimentos , Microbiología de Alimentos , Enfermedades Transmitidas por los Alimentos/microbiología , Enfermedades de las Plantas/inmunología , Enfermedades de las Plantas/microbiología , Hojas de la Planta/microbiología , Tabaco/microbiología , Sistemas de Secreción Tipo III/genética
14.
J Food Sci ; 84(10): 2736-2744, 2019 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-31573690

RESUMEN

Controlling the free chlorine (FC) availability in wash water during sanitization of fresh produce enhances our ability to reduce microbial levels and prevent cross-contamination. However, maintaining an ideal concentration of FC that could prevent the risk of contamination within the wash system is still a technical challenge in the industry, indicating the need to better understand wash water chemistry dynamics. Using bench-scale experiments and modeling approaches, we developed a comprehensive mathematical model to predict the FC concentration during fresh-cut produce wash processes for different lettuce types (romaine, iceberg, green leaf, and red leaf), carrots, and green cabbage as well as Escherichia coli O157:H7 cross-contamination during fresh-cut iceberg lettuce washing. Fresh-cut produce exudates, as measured by chemical oxygen demand (COD) levels, appear to be the primary source of consumption of FC in wash water, with an apparent reaction rate ranging from 4.74 × 10 - 4 to 7.42 × 10 - 4 L/mg·min for all produce types tested, at stable pH levels (6.5 to 7.0) in the wash water. COD levels increased over time as more produce was washed and the lettuce type impacted the rate of increase in organic load. The model parameters from our experimental data were compared to those obtained from a pilot-plant scale study for lettuce, and similar reaction rate constant (5.38 × 10-4 L/mg·min) was noted, supporting our hypothesis that rise in COD is the main cause of consumption of FC levels in the wash water. We also identified that the bacterial transfer mechanism described by our model is robust relative to experimental scale and pathogen levels in the wash water. Finally, we proposed functions that quantify an upper bound on pathogen levels in the water and on cross-contaminated lettuce, indicating the maximum potential of water-mediated cross-contamination. Our model results could help indicate the limits of FC control to prevent cross-contamination during lettuce washing.


Asunto(s)
Cloro/metabolismo , Escherichia coli O157/aislamiento & purificación , Manipulación de Alimentos , Cloro/análisis , Recuento de Colonia Microbiana , Escherichia coli O157/genética , Escherichia coli O157/crecimiento & desarrollo , Contaminación de Alimentos/análisis , Manipulación de Alimentos/métodos , Microbiología de Alimentos , Humanos , Lechuga/química , Lechuga/microbiología , Modelos Biológicos , Hojas de la Planta/química , Hojas de la Planta/microbiología , Verduras/química , Verduras/microbiología
15.
J Food Sci ; 84(10): 2916-2924, 2019 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-31502678

RESUMEN

A method combining surface-enhanced Raman scattering (SERS) with a lateral flow strip (LFS) was developed for the quantitative and sensitive analysis of Escherichia coli O157:H7. AuMBA @Ag nanoparticles were prepared as SERS probes, and 4-methylthiobenzoic acid (MBA) as a Raman reporter was inserted into the interior gap of the Au@Ag core-shell nanoparticles, which replaced the Au nanoparticles that serve as SERS nanotags in traditional LFS. Using this developed SERS-LFS, the presence of the target bacteria could be tested through the appearance of a red band on the test line. Furthermore, quantitative analysis of E. coli O157:H7 was achieved by measuring the specific Raman intensity of MBA on the test line. The sensitivity of this SERS-LFS biosensor is 5 × 104 CFU/mL of E. coli O157:H7, which is 10-fold higher than that of a naked eye-based colorimetric LFS. This quantitative detection of E. coli O157:H7 ( Y = 1993.86 X - 6812.17, R2 = 0.9947) was obtained with a wide linear range (5 × 104 to 5 × 108 ) due to the signal enhancement of the SERS nanotags. In addition, the SERS-LFS could differentiate E. coli O157:H7 from closely related bacterial species or nontarget contaminants, suggesting high specificity of this assay. The applicability of SERS-LFS to the analysis of E. coli O157:H7 in milk, chicken breast, and beef was also validated, indicating that the sensitivity was not disturbed by the food matrix. In summary, the SERS-LFS developed in this study could be a powerful tool for the quantitative and sensitive screening of E. coli O157:H7 in a food matrix. PRACTICAL APPLICATION: This study demonstrates that a surface-enhanced Raman scattering (SERS)-based lateral flow strip (LFS) could be used as a rapid and sensitive method for Escherichia coli O157:H7 detection. Furthermore, this SERS-based LFS could achieve quantitative detection of the target, eliminating the defect of the traditional colloidal gold LFS, which is not quantifiable.


Asunto(s)
Escherichia coli O157/aislamiento & purificación , Nanopartículas del Metal/química , Plata/química , Espectrometría Raman/métodos , Animales , Bovinos , Escherichia coli O157/genética , Escherichia coli O157/crecimiento & desarrollo , Leche/microbiología , Sensibilidad y Especificidad , Espectrometría Raman/instrumentación
16.
PLoS Pathog ; 15(8): e1007652, 2019 08.
Artículo en Inglés | MEDLINE | ID: mdl-31404118

RESUMEN

Enterohemorrhagic Escherichia coli O157:H7 (EHEC) is an important food-borne pathogen that colonizes the colon. Transposon-insertion sequencing (TIS) was used to identify genes required for EHEC and E. coli K-12 growth in vitro and for EHEC growth in vivo in the infant rabbit colon. Surprisingly, many conserved loci contribute to EHEC's but not to K-12's growth in vitro. There was a restrictive bottleneck for EHEC colonization of the rabbit colon, which complicated identification of EHEC genes facilitating growth in vivo. Both a refined version of an existing analytic framework as well as PCA-based analysis were used to compensate for the effects of the infection bottleneck. These analyses confirmed that the EHEC LEE-encoded type III secretion apparatus is required for growth in vivo and revealed that only a few effectors are critical for in vivo fitness. Over 200 mutants not previously associated with EHEC survival/growth in vivo also appeared attenuated in vivo, and a subset of these putative in vivo fitness factors were validated. Some were found to contribute to efficient type-three secretion while others, including tatABC, oxyR, envC, acrAB, and cvpA, promote EHEC resistance to host-derived stresses. cvpA is also required for intestinal growth of several other enteric pathogens, and proved to be required for EHEC, Vibrio cholerae and Vibrio parahaemolyticus resistance to the bile salt deoxycholate, highlighting the important role of this previously uncharacterized protein in pathogen survival. Collectively, our findings provide a comprehensive framework for understanding EHEC growth in the intestine.


Asunto(s)
Elementos Transponibles de ADN , Infecciones por Escherichia coli/microbiología , Escherichia coli O157/crecimiento & desarrollo , Proteínas de Escherichia coli/metabolismo , Intestinos/microbiología , Factores de Virulencia/metabolismo , Animales , Infecciones por Escherichia coli/genética , Infecciones por Escherichia coli/metabolismo , Escherichia coli O157/genética , Escherichia coli O157/aislamiento & purificación , Proteínas de Escherichia coli/genética , Regulación Bacteriana de la Expresión Génica , Conejos , Análisis de Secuencia de ADN , Factores de Virulencia/genética
17.
Food Microbiol ; 84: 103241, 2019 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-31421768

RESUMEN

Bacterial persistence is a form of phenotypic heterogeneity in which a subpopulation, persisters, has high tolerance to antibiotics and other stresses. Persisters of enteric pathogens may represent the subpopulations capable of surviving harsh environments and causing human infections. Here we examined the persister populations of several shiga toxin-producing Escherichia coli (STEC) outbreak strains under conditions relevant to leafy greens production. The persister fraction of STEC in exponential-phase of culture varied greatly among the strains examined, ranging from 0.00003% to 0.0002% for O157:H7 strains to 0.06% and 0.08% for STEC O104:H4 strains. A much larger persister fraction (0.1-11.2%) was observed in STEC stationary cells grown in rich medium, which was comparable to the persister fractions in stationary cells grown in spinach lysates (0.6-3.6%). The highest persister fraction was measured in populations of cells incubated in field water (9.9-23.2%), in which no growth was detected for any of the STEC strains examined. Considering the high tolerance of persister cells to antimicrobial treatments and their ability to revert to normal cells, the presence of STEC persister cells in leafy greens production environments may pose a significant challenge in the development of effective control strategies to ensure the microbial safety of fresh vegetables.


Asunto(s)
Escherichia coli O157/crecimiento & desarrollo , Microbiología de Alimentos , Escherichia coli Shiga-Toxigénica/crecimiento & desarrollo , Verduras/microbiología , Inocuidad de los Alimentos , Factores de Virulencia
18.
Future Microbiol ; 14: 885-898, 2019 07.
Artículo en Inglés | MEDLINE | ID: mdl-31368788

RESUMEN

Aim: The aim of this study is to formulate a new single nonselective pre-enrichment medium (ELSS) that can support the concurrent growth of four major foodborne pathogens containing E. coli O157: H7, L. monocytogenes, S. aureus and S. enterica serovar Entertidis to develop a multiplex TaqMan Real-time PCR (mRT-PCR). Methods: The mRT-PCR with a new pre-enrichment was carried out for simultaneous detection and quantification of these foodborne bacteria. Results: By using mRT-PCR after 16 h pre-enrichment in ELSS, the detection limit of each pathogen was 1 CFU/25 ml contaminated milk, as well as inclusivity and exclusivity reached 100%. Conclusion: The mRT-PCR assay with pre-enrichment step is a fast and reliable technique for detecting single or multiple pathogens in food products.


Asunto(s)
Bacterias/genética , Técnicas Bacteriológicas/métodos , Microbiología de Alimentos/métodos , Enfermedades Transmitidas por los Alimentos/microbiología , Leche/microbiología , Animales , Bacterias/crecimiento & desarrollo , Bacterias/aislamiento & purificación , Medios de Cultivo , ADN Bacteriano/genética , Escherichia coli O157/genética , Escherichia coli O157/crecimiento & desarrollo , Escherichia coli O157/aislamiento & purificación , Listeria monocytogenes/genética , Listeria monocytogenes/crecimiento & desarrollo , Listeria monocytogenes/aislamiento & purificación , Reacción en Cadena de la Polimerasa , Salmonella enteritidis/genética , Salmonella enteritidis/crecimiento & desarrollo , Salmonella enteritidis/aislamiento & purificación , Sensibilidad y Especificidad , Staphylococcus aureus/genética , Staphylococcus aureus/crecimiento & desarrollo , Staphylococcus aureus/aislamiento & purificación
19.
ACS Appl Mater Interfaces ; 11(34): 31411-31420, 2019 Aug 28.
Artículo en Inglés | MEDLINE | ID: mdl-31373785

RESUMEN

Cutaneous hemorrhage often occurs in daily life which may cause infection and even amputation. This research aims to develop a novel chitosan dressing impregnated with ZnO/N-halamine hybrid nanoparticles for quick antibacterial performance, outstanding hemostatic potential, high porosity, and favorable swelling property through combining sonication and lyophilization processing. After 30 days of storage, about 90% bacterial cell viability loss could be observed toward both Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli O157:H7 within 30 min of contact by colony counting method. The hybrids assembled much more platelet and red blood cell as compared with pure chitosan control. Moreover, the lower blooding clotting index value gave evidence that these composites could control hemorrhaging and reduce the probability of wound infection. No potential skin irritation and toxicity were detected using in vitro cytocompatibility and a skin stimulation test. Therefore, this work demonstrated a facile and cost-effective approach for the preparation of N-halamine-based hybrid sponges which show promising application for wound dressings.


Asunto(s)
Antibacterianos , Vendajes , Escherichia coli O157/crecimiento & desarrollo , Staphylococcus aureus/crecimiento & desarrollo , Óxido de Zinc , Animales , Antibacterianos/química , Antibacterianos/farmacología , Coagulación Sanguínea/efectos de los fármacos , Viabilidad Microbiana/efectos de los fármacos , Conejos , Óxido de Zinc/química , Óxido de Zinc/farmacología
20.
Food Funct ; 10(9): 5843-5852, 2019 Sep 01.
Artículo en Inglés | MEDLINE | ID: mdl-31464316

RESUMEN

Enterohemorrhagic Escherichia coli (EHEC) is a strain of human pathogenic E. coli bacteria that can cause serious foodborne diseases. Many probiotics have antagonistic effects on EHEC, but few studies have examined the interactions between probiotics and EHEC in vivo. To investigate the colonization of Lactobacillus casei LC2W and its inhibitory effect on E. coli O157:H7 in vivo, these strains labelled with different fluorescent proteins were monitored in the intestinal tracts of live mice using an in vivo imaging system. The results showed that L. casei LC2W inhibited the colonization of O157:H7 in mice. Further research found that LC2W had both prevention and treatment effects on the colitis severity of mice infected by O157:H7, where the prevention effect dominated over the treatment one. This study demonstrates a feasible method for studying the interactions between probiotics and pathogens, and the mechanisms by which probiotics reduce colitis induced by O157:H7.


Asunto(s)
Colitis/tratamiento farmacológico , Infecciones por Escherichia coli/tratamiento farmacológico , Escherichia coli O157/crecimiento & desarrollo , Lactobacillus casei/fisiología , Probióticos/administración & dosificación , Animales , Colitis/microbiología , Infecciones por Escherichia coli/microbiología , Escherichia coli O157/efectos de los fármacos , Escherichia coli O157/fisiología , Humanos , Intestinos/microbiología , Masculino , Ratones , Ratones Endogámicos C57BL
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