Antimicrobial activity of eugenol and carvacrol against Salmonella enterica and E. coli O157:H7 in falafel paste at different storage temperatures.

The objectives of the current study were: i) to investigate the antimicrobial activity of 0.125, 0.250 and 0.50 % (7.54, 15.08 and 30.17 mmol/Kg of eugenol) and (8.15, 16.31, and 33.61 mmol/Kg of carvacrol) against S. enterica and E. coli O157:H7 in falafel paste (FP) stored at 4, 10 or 25 °C for 10 d; and ii) to study the sensory properties of fried falafel treated with eugenol and carvacrol. S. enterica grew well in untreated falafel (control) samples at 10 and 25 °C, while E. coli O157:H7 grew only at 25 °C. However, numbers of S. enterica and E. coli O157:H7 in FP stored at 4 °C were reduced by 1.4-1.6 log CFU/g after 10 d. The antimicrobial agents were more effective at 25 °C against S. enterica, but were better at 4 and 10 °C against E. coli O157:H7. Addition of 0.125-0.5 % eugenol or carvacrol reduced the S. enterica numbers to undetectable level by direct plating (2 log CFU/g) by 2-10 d at 25 °C. FP samples treated with 0.5 % eugenol or 0.25-0.5 % carvacrol were negative for S. enterica cells by enrichment (1 CFU/5 g) by 10 d at 25 °C. In contrast, viable E. coli O157:H7 were not detected by direct plating when FP was treated with 0.25-0.5 % carvacrol or 0.5 % eugenol and stored at 4 °C by 2 d. Addition of eugenol or carvacrol did not affect the color, texture, and appearance of fried falafel but decreased the flavor and overall acceptability scores compared to untreated falafel. Using eugenol and carvacrol as natural antimicrobials have the potential to enhance the safety of FP by reducing the threat from foodborne pathogens.

The Role of Communication and Commitment in COVID-19 Knowledge, Attitudes, and Behaviors Among University Students in Jordan: Interaction and Analysis.

INTRODUCTION: Several fields, such as public health, economy, and science, have been adversely affected by the COVID-19 pandemic. The objectives of the present study were to investigate knowledge, attitudes, communication, commitment, and behavioral practices of Jordan university students; and using structural equation modelling (SEM) to investigate the relationship among COVID-19 knowledge, attitude, communication, commitment and behavioral practices of students. METHODS: In this cross-sectional study, the primary data were collected from 1,095 students comprising 298 males (27.21%) and 797 females (72.79%) from three major universities in Jordan using an online-based questionnaire. RESULTS: It was found that scores of knowledge, attitudes, communication, commitment, and behavioral practices of students about COVID-19 were 81.4, 79.3, 70.0, 72.6, and 67.4%, respectively. The results also showed that significant association the variables of knowledge and attitudes as well as the commitment and communication are partial mediators in this relationship. Further, a clear positive relationship was observed between the communication, commitment, and behavioral practices of students. CONCLUSIONS: This study confirms the importance of communication and commitment to generate proactive behavioral practices.

Survival of Salmonella enterica and Listeria monocytogenes in date palm paste and syrup at different storage temperatures.

This study aimed to investigate the behavior of Salmonella enterica and Listeria monocytogenes in processed date paste and syrup at different temperatures. Commercial products were inoculated with approximately 6 log CFU/mL of S. enterica or L. monocytogenes and stored at 4, 10, and 24°C for 90 days. S. enterica was able to survive in date products until the end of storage at 4°C. At this temperature, numbers decreased by 2.1 log CFU/g in date paste and by 3.4 log CFU/g in date syrup; however, at 10°C, cells were reduced >4.2 log CFU/g and were undetectable by direct plating in date paste or by enrichment (complete elimination) in syrup. Further, at 24°C, complete elimination of S. enterica was achieved in date paste and syrup by 30 and 7 days, respectively. L. monocytogenes numbers decreased by 1.4, 4.4, and >4.6 log CFU/g in date paste stored at 4, 10, and 24°C for 90 days, respectively. In date syrup, numbers of L. monocytogenes decreased to undetectable levels by 50, 14, and 4 days at 4, 10, and 24°C, respectively, by direct plating and complete elimination was observed at 10 and 24°C by 50 and 30 days of storage, respectively. The initial pH values of date paste and syrup were 4.7 and 4.8, respectively, and remained stable until the end of storage except for L. monocytogenes-inoculated syrup. PRACTICAL APPLICATION: Salmonella enterica and Listeria monocytogenes can easily survive in date paste and syrup particularly at refrigerator temperature, which explains the necessity of preventing the contamination of date products with foodborne pathogens.

Chitosan-ZnO nanocomposite coating for inhibition of Listeria monocytogenes on the surface and within white brined cheese.

Several types of cheeses including white brined cheese have been linked to listeriosis outbreaks worldwide. This study aimed to (i) investigate the in vitro inhibitory activity of zinc oxide (ZnO) nanoparticles (NPs) at concentrations of 0.0125-0.1% against three Listeria monocytogenes strains at 10 or 37°C, (ii) evaluate the antimicrobial efficiency of chitosan-based coating containing 1.0% ZnO NPs against L. monocytogenes on the surface or inside vacuum-packaged white brined cheese at 4 or 10°C, and iii) determine the migration of ZnO NPs from the surface to the interior of cheeses using energy dispersive X-ray analysis (EDX). The antimicrobial activity of ZnO NPs was higher at 37°C than at 10°C. The initial numbers (4.0 log CFU/ml) of two L. monocytogenes strains were reduced below detectable levels, while the third strain was reduced by 1.2 log CFU/ml at 37°C. At 10°C, the initial L. monocytogenes numbers were reduced by 0.4-1.9 log CFU/ml. Chitosan coating containing 1.0% ZnO NPs reduced L. monocytogenes numbers by 1.5 and 3.7 log CFU/g on the surface or by 0.9 and 1.5 log CFU/g in the interior of vacuum-packed cheese stored at 10 or 4°C, respectively. The EDX results showed that ZnO NP levels remained constant on the cheese surface with no indication of migration into the cheese matrix at the end of storage. Practical Application: Chitosan and ZnO are antimicrobial agents and their combination in edible coatings has the potential for inactivating foodborne pathogens. Chitosan coating containing ZnO NPs can be used as an effective active packaging material to reduce numbers of L. monocytogenes in white brined cheese.

Inactivation of stressed Salmonella enterica, Escherichia coli O157:H7, and Listeria monocytogenes in hummus using low dose gamma irradiation.

Hummus is a popular dip in the Middle East region prepared by mixing the boiled chickpeas with tahini and other ingredients, and because its consumption has increased world-wide some notoriety has developed following an increase in the incidence of hummus-related illness outbreaks and recalls. The objectives of the current research were (i) to study the efficiency of low dose gamma irradiation to inhibit Escherichia coli O157:H7, Salmonella enterica, and Listeria monocytogenes in hummus, and (ii) to assess the effect of environmental stresses namely cold, heat, and desiccation on the resistance of these pathogens to gamma irradiation. The samples of hummus were prepared and then individually inoculated with approximately 7.0 log CFU/g of unstressed or cold-, heat-, or desiccated-stressed cocktail cultures of each of E. coli O157:H7, S. enterica, and L. monocytogenes. The inoculated samples were then exposed to gamma irradiation at doses of 0.1 to 0.6 kGy. The numbers of unstressed E. coli O157:H7, S. enterica, and L. monocytogenes were decreased by 0.6-3.9, 0.7-2.9, and 1.0-3.0 log CFU/g, respectively, by irradiation treatment. The resistance of E. coli O157:H7 to gamma irradiation was not affected by desiccation, heat, and cold stresses. However, the pre-exposure of S. enterica and L. monocytogenes cells to these stresses reduced their resistance toward gamma irradiation. PRACTICAL APPLICATION: Gamma irradiation is a non-thermal treatment that can be used in food processing to ensure food safety and quality. The current study proved that low levels (≤0.6 kGy) of gamma irradiation can effectively decrease the risk of unstressed and cold-, heat-, or desiccation-stressed Salmonella enterica, Listeria monocytogenes, or Escherichia coli O157:H7 in hummus.

Use of citric acid and garlic extract to inhibit Salmonella enterica and Listeria monocytogenes in hummus.

Recently, the consumption of hummus has become popular in the United States, European countries, and Canada, and unfortunately, several foodborne outbreaks and recalls have been reported due to its contamination with Listeria monocytogenes and Salmonella enterica. The current study aimed to investigate the inhibitory activity of 0.5, 1.0, and 1.5% citric acid (CA) and 1.0, 2.0 and 3.0% garlic extract (GE) toward S. enterica and L. monocytogenes in hummus stored at 4, 10 and 24 °C. L. monocytogenes grew well in untreated (control) hummus samples at all tested temperatures, whereas S. enterica grew only at 10 and 24 °C. CA at 0.5 to 1.5% reduced L. monocytogenes numbers by 3.0-3.3 log CFU/g at 4 °C, 1.7-3.9 log CFU/g at 10 °C, and 0.9-1.4 log CFU/g at 24 °C. Numbers of S. enterica were reduced by 0.6-1.7, 4.1-4.9 and <1.5 log CFU/g, at 4, 10 and 24 °C, respectively, compared to the control during 10 d storage. GE at 1.0-3.0% also reduced numbers of L. monocytogenes at 10 d by 0.7-3.0, and 1.3-3.6 log CFU/g at 4 and 10 °C, respectively, and numbers of S. enterica by 0.7-1.2, 1.8-2.6 and 0.5-1.6 log CFU/g, at 4, 10 and 24 °C, respectively, compared to the control. Chromatographic analysis of GE revealed the presence of four organosulfur compounds including diallyl disulfide, diallyl trisulfide, 2-vinyl-(4H)-1,3-dithiin and 3-vinyl-(4H)-1,2-dithiin where the latter was the predominant compound with a level of 22.9 mg/g which significantly contributed to the inhibitory effect of GE. CA and GE are adequate natural antimicrobials in hummus to reduce L. monocytogenes and S. enterica numbers and enhance product safety.

Conductometric Immunosensor for Escherichia coli O157:H7 Detection Based on Polyaniline/Zinc Oxide (PANI/ZnO) Nanocomposite.

A conductometric immunosensor was developed for the detection of one of the most common foodborne pathogens, Escherichia coli O157:H7 (E. coli O157:H7), by conductometric sensing. The sensor was built based on a polyaniline/zinc oxide (PANI/ZnO) nanocomposite film spin-coated on a gold electrode. Then, it was modified with a monoclonal anti-E. coli O157:H7 antibody as a biorecognition element. The fabricated nanostructured sensor was able to quantify the pathogens under optimal detection conditions, within 30 min, and showed a good detection range from 101 to 104 CFU/mL for E. coli O157:H7 and a minimum detection limit of 4.8 CFU/mL in 0.1% peptone water. The sensor efficiency for detecting bacteria in food matrices was tested in ultra-heat-treated (UHT) skim milk. E. coli O157:H7 was detected at concentrations of 101 to 104 CFU/mL with a minimum detection limit of 13.9 CFU/mL. The novel sensor was simple, fast, highly sensitive with excellent specificity, and it had the potential for rapid sample processing. Moreover, this unique technique for bacterial detection could be applicable for food safety and quality control in the food sector as it offers highly reliable results and is able to quantify the target bacterium.

Survival and growth of Listeria monocytogenes and Staphylococcus aureus in ready-to-eat Mediterranean vegetable salads: Impact of storage temperature and food matrix.

This study aimed to evaluate the survival or growth behavior of L. monocytogenes and S. aureus in ready-to-eat vegetable salads including Arabic salad (tomato-cucumber salad) with or without 0.5% (w/w) salt and 1% (v/w) lemon juice, tahini salad, coleslaw salad, toum sauce salad (aioli) stored at 4, 10, and 24 °C for 5 d. L. monocytogenes showed greater growth or survival in all types of salads at all temperatures tested. L. monocytogenes grew in Arabic salad without additives at 10 °C and tahini salad at 4 and 10 °C. L. monocytogenes survived all preparation and storage conditions used in the current study and its numbers were detectable in all types of salads tested, and with a maximum reduction of 3.0 log CFU/g, except for toum sauce salad at 24 °C, the cells were not detected using enrichment broth. In addition, S. aureus survived in Arabic salad with or without additives and in tahini salad with a maximum reduction of 2.3 log CFU/g. However, S. aureus numbers sharply decreased in coleslaw and toum sauce salad and at 5 d they reached undetectable levels (≥2 log CFU/g) in coleslaw at 24 °C and in toum sauce at 10 and 24 °C. Addition of lemon juice and salt to Arabic salad significantly reduced the numbers of both pathogens.

Antagonistic effects of Lactobacillus reuteri against Escherichia coli O157:H7 in white-brined cheese under different storage conditions.

This study aimed to investigate the survival of the foodborne pathogen Escherichia coli O157:H7 in white-brined cheeses as influenced by the presence of Lactobacillus reuteri. The white cheeses were made from pasteurized bovine milk inoculated with E. coli O157:H7 (cocktail of 3 strains) to achieve ∼5 log10 cfu/g with absence or presence of Lb. reuteri (∼6 log10 cfu/g). Cheese samples were brined in 10% or 15% NaCl solution and stored at 10°C and 25°C for 28 d. The white-brined cheeses were assessed for salt content, pH, water activity (Aw), and numbers of E. coli O157:H7, Lb. reuteri, nonstarter lactic acid bacteria (NSLAB), yeasts, and molds. Results showed that E. coli O157:H7 survived in cheese stored in both brine solutions at 10°C and 25°C regardless of the presence of Lb. reuteri. A substantial reduction was observed in cheese stored in 10% NaCl brine at 25°C, followed by cheese stored in 15% NaCl brine at 10°C by 2.64 and 2.16 log10 cfu/g, respectively, in the presence of Lb. reuteri and by 1.02 and 1.87 log10 cfu/g, respectively, in the absence of Lb. reuteri under the same conditions. The pathogen in brine solutions survived but at a lower rate. Furthermore, the growth of Lb. reuteri and NSLAB were enhanced or slightly decreased in cheese and brine by 28 d, respectively. The salt concentrations of cheese ranged from 4 to 6% and 5 to 7% (wt/wt), during 28-d ripening in 10 and 15% brine, respectively. Values of pH and Aw slightly increased at d 1 after exposure to brine and reached 4.69 to 6.08 and 0.91 to 0.95, respectively, in all treatments. Therefore, the addition of Lb. reuteri can be used as a biopreservation method to inhibit the survival of E. coli O157:H7 in white-brined cheese when combined with the appropriate temperature, NaCl level, and storage time.

Food Safety During and After the Era of COVID-19 Pandemic.

The coronavirus disease 2019 (COVID-19) is a clinical syndrome caused by severe acute respiratory syndrome corona virus-2 (SARS-CoV-2). COVID-19 was declared a pandemic by the World Health Organization (WHO) on March 11, 2020 due to its rapid and extensive spread among many countries through its very contagious nature and its high mortality among the elderly and infirm. Recently, data on the survival of SARS-CoV-2 on contact surfaces has been reported, but there is none on the survival of COVID-19 on food surfaces and packages. The potential survival and transmission of SARS-CoV-2 on/via food and packages are discussed based on data available for other respiratory viruses such as SARS-CoV and MERS-CoV. However, studies are needed to explore its transmission via food and survival on food packaging materials. The implementation of food safety management systems such as Hazard Analysis and Critical Control Points (HACCP), and Good Manufacturing Practices (GMP) are important to reduce the risk of COVID-19 infection. Cleaning, sanitation, good hygienic practices, and active packaging are also needed from farm to fork.

Attitudes, Anxiety, and Behavioral Practices Regarding COVID-19 among University Students in Jordan: A Cross-Sectional Study.

The COVID-19 pandemic represents a major public health, economic, political, and scientific concern in most countries around the globe where COVID-19 cases and deaths have been confirmed. This study assessed the attitudes, anxiety, and behavioral practices of university students in Jordan regarding COVID-19 during the early period of the infection (March 19-21, 2020) using a validated, self-administered survey questionnaire. Positive attitudes or low-risk practices were given 1 point, whereas negative attitudes or high-risk practices were scored 0. Percentages of the total score were used for categorizing data into negative attitudes or high-risk practices (≤ 60%), moderate attitudes or moderate-risk practices (60.01-80%), and positive attitudes or low-risk practices (> 80%). Generally, the university students displayed positive attitudes and low-risk practices toward preventing COVID-19, with an average score of 81.1% and 84.3%, respectively. Approximately two-thirds (69.1%) of the students showed a positive attitude toward COVID-19 seriousness, concern of contracting the virus, and the appropriate prevention measures, and low-risk practices (67.6%) toward preventing COVID-19 including implementation of social distancing and good hygiene. Female, older, medical, or postgraduate students practiced significantly more (P ≤ 0.05) appropriate hygiene and social distancing behaviors toward COVID-19 than their counterparts of each group. More than two-thirds (69.2%) of the students were anxious that they might become infected with COVID-19. These results are important for health authorities to develop appropriate educational programs and protective health measures including good respiratory etiquette and handwashing practices, to enhance safer lifestyles and prevent COVID-19 transmission.

Factors affecting the viability of Staphylococcus aureus and production of enterotoxin during processing and storage of white-brined cheese.

Staphylococcus aureus is a major foodborne pathogen that causes severe disease in humans. It is commonly found in milk and dairy products, particularly in fresh brined cheese. Our aim was to investigate the behavior of Staph. aureus and enterotoxin production during the storage of white-brined cheese prepared with or without a starter culture and stored in a 10 or 15% NaCl brine at 10°C and 25°C for 28 d. NaCl concentration, water activity, pH, and number of Staph. aureus and lactic acid bacteria were determined in cheese and brine. Only 1 of 4 Staph. aureus strains (ATCC 439) was positive for enterotoxin production, and its production was detected in unsalted UHT milk, but not in salted milk or in any of the cheese treatments held at 37°C for 1, 3, or 7 d. Staphylococcus aureus grew in the cheese stored in both brines at 10°C and 25°C, regardless of the presence of a starter culture, although the latter significantly reduced Staph. aureus growth in cheese or its brine at 10°C. Staphylococcus aureus numbers were increased by 2.26 and 0.47 log10 cfu/g in cheese stored in 10 and 15% NaCl brine, respectively, in the presence of starter culture, and by 2.78 and 2.96 log10 cfu/g, respectively, in the absence of starter culture at 10°C. Nonetheless, the pathogen grew, but at a lower number in the brines. The salt concentration of cheese stored in 10% brine remained at approximately 5% during storage; however, in 15% brine, the salt concentration increased to almost 8% (wt/wt) by 28 d. The addition of a starter culture, high salt concentration, low temperature, and pH (∼5.2) had inhibitory effects on the growth of Staph. aureus. Moreover, lactic acid bacterial numbers increased considerably in cheese and brine by d 28. The use of starter cultures, salt (15%), and low storage temperature (10°C) reduced the growth of Staph. aureus, and salt may have prevented enterotoxin production in white-brined cheese.

Knowledge and Information Sources About COVID-19 Among University Students in Jordan: A Cross-Sectional Study.

Background: Coronavirus disease 2019 (COVID-19) has rapidly spread worldwide, and it was officially declared to be a pandemic by the World Health Organization (WHO) on March 11, 2020. Most countries over the entire globe have reported some COVID-19 cases. The current study aimed to assess student knowledge about COVID-19 at different Jordanian universities and determine where they sourced their information. Methods:A cross-sectional study was conducted among 2,083 undergraduate or postgraduate students from different governmental and private universities during the initial stage of the disease in Jordan (March 19-21, 2020) using a validated, structured, self-administered, online questionnaire. The survey was structured to assess their knowledge about viral sources, incubation period, mortality rate, transmission, symptoms and complications as well as the source of information about COVID-19. Results:Overall, 56.5% of the respondents showed good knowledge and almost 40.5% showed moderate knowledge. On the other hand, 3.0% of the participants showed poor knowledge about COVID-19. The average knowledge score of students was 80.1%, which is considered to be within the scale of good knowledge. Both the college of study and educational level significantly (P < 0.05) associated with student knowledge. Students who majored in medical sciences showed the highest mean score of 82.8%, with 69.0% displaying a good knowledge level. Postgraduate students had significantly higher knowledge scores compared to undergraduate students. The majority of students used the internet, social media and mass media as sources of information about COVID-19. Scientific websites and articles were used more commonly by medical and postgraduate students. Conclusions:The COVID-19 pandemic is a major challenge to the health of the world population; therefore, these results assessing students' knowledge provide an important baseline for planning required educational interventions such as contact tracing and self-quarantine. These results may also help public health authorities by engaging communities in implementation of protective health measures, including positive hygienic practices such as hand washing to reduce the risk of COVID-19.

Inactivation of Salmonella spp. in tahini using plant essential oil extracts.

Tahini is a popular food product in the Middle East region and is used as a major ingredient in several ready-to-eat food products. Tahini and its products have been linked to foodborne illness outbreaks and product recalls worldwide as a result of Salmonella spp. contamination. The objectives of the current study were to investigate: i) the effectiveness of 10 plant essential oil extracts on the viability of Salmonella spp. using disc diffusion ii) the antimicrobial activity of the most effective oils against Salmonella spp. in commercial or 10% w/v hydrated tahini (tahini-based product model) stored at 37, 25 and 10 °C for 28 d and iii) the effect of the addition of essential oil extracts on the sensory acceptability of tahini and hydrated tahini. Among the tested essential oils, thyme (TO) and cinnamon oil (CO) showed the highest antimicrobial activity against tested Salmonella spp. at 37 and 10 °C using a disc diffusion assay method. In tahini, the addition of 2.0% CO reduced the numbers of Salmonella spp. by 2.87, 2.64 or 2.35 log10 CFU/ml at 37, 25 or 10 °C, respectively, by 28 d. However, the antimicrobial activity of CO was more pronounced at all storage temperatures in hydrated tahini where no viable cells were detected after 3 d storage at 25 and 37 °C, or after 7 d at 10 °C. However, at 25 and 37 °C, the antimicrobial activity of CO was more evident since no viable cells were detected after 14 d when 0.5% was used. The numbers of Salmonella spp. were reduced by 3.29, 3.03 or 2.17 log10 CFU/ml at 37, 25 or 10 °C, respectively, after 28 d when 2.0% TO was added to tahini. Salmonella spp. were not detected in the hydrated tahini treated with 2.0% TO after 28 d at 37 °C or 25 °C, while at 10 °C, the numbers of Salmonella spp. were not significantly reduced after 28 d in hydrated tahini compared to the initial numbers at zero time. Therefore, the addition of TO and CO could be used to preclude the post process contamination of tahini with foodborne pathogens, yet, the addition of TO and CO to tahini reduced its consumer acceptability compared untreated tahini.

The Use of Malic and Acetic Acids in Washing Solution to Control Salmonella spp. on Chicken Breast.

Salmonella is a persisting contaminant in poultry products that may pose a potential risk to consumers. Thus, developing decontamination strategies to eliminate or reduce this pathogen in chicken is crucial. The objective of the current study was to investigate the antimicrobial activity of malic acid (MA) and acetic acid (AA) or their combination against Salmonella on chicken breast at 4 °C for 10 days. The effect of storage temperature (4 and 21 °C) on Salmonella inactivation was also investigated for up to 21 days. Five serovars of Salmonella were inoculated in a model Mueller-Hinton (MH) broth system to a level of about 7 log10 CFU/mL and the broth was treated with 5 mg/mL of each of MA, AA or their combination. AA was more effective than MA in the model system at 21 °C, where it resulted in total elimination of Salmonella, but MA was more effective in eliminating Salmonella at 4 °C. However, the combined MA and AA solutions were more effective than either MA or AA alone. When applying washing solutions containing 5 mg/mL of either of MA, AA, or their combination to chicken breast inoculated with about 5 log10 CFU/g, the MA+AA washing solution was the most effective. It resulted in complete elimination of Salmonella from chicken breast and rendered a significant reduction in mesophilic aerobic bacteria and lactic acid bacteria numbers. PRACTICAL APPLICATION: This study indicates that the use of a washing solution containing MA and AA could improve the safety and extend the shelf life of raw chicken by substantially reducing Salmonella and contaminating microflora on the product.

Control of Salmonella enterica and Listeria monocytogenes in hummus using allyl isothiocyanate.

Hummus (chickpea dip) is a ready-to-eat product which has been implicated in several foodborne outbreaks and food recalls. This study aimed to screen the antimicrobial activity of allyl isothiocyanate (AITC) against 5 strains of each of Salmonella enterica and Listeria monocytogenes using a disc diffusion method. Additionally, the antimicrobial activity of 0.1-1.5% (v/w) AITC against both pathogens and aerobic bacteria in hummus was also investigated. The inhibition zones of AITC were 8.5-15 and 7.0-8.5 mm against the S. enterica and L. monocytogenes strains, respectively, at 37 °C. S. enterica numbers were reduced by >6 log10 CFU/g in hummus containing ≥0.5% AITC by 3 days at both 4 and 10 °C. While 0.1-0.25% AITC reduced S. enterica by 2.5-5.1 log10 CFU/g at 4 °C or by 4.7-6.0 log10 CFU/g at 10 °C by 10 days. Similarly, L. monocytogenes numbers decreased by >6 log10 CFU/g in hummus with ≥0.5% or ≥1.0% AITC at 4 or 10 °C, respectively, by 3 days. Further, 0.25% AITC significantly reduced L. monocytogenes in hummus by 2.7 and 4.3 log10 CFU/g at 4 and 10 °C, respectively. Moreover, 0.1% AITC reduced L. monocytogenes by 1.8 log10 CFU/g in hummus at 10 °C and inhibited the growth at 4 °C for up to 10 days. The aerobic bacterial count also significantly decreased in un-inoculated hummus treated with 1.0-1.5% AITC at both 4 and 10 °C, while a concentration of 0.25-0.5% AITC inhibited their growth at 4 °C. AITC can be used to reduce the risk of salmonellosis or listeriosis in hummus and extend its shelf-life.

Use of acetic and citric acids to inhibit Escherichia coli O157:H7, Salmonella Typhimurium and Staphylococcus aureus in tabbouleh salad.

The objective of the current study was to evaluate the antimicrobial action of different concentrations of acetic (0.3% and 0.4%) or citric (1% and 1.4%) acids and their combinations (1% citric acid plus 0.4% acetic acid and 1.4% citric acid plus 0.3% acetic acid) against Salmonella Typhimurium, Escherichia coli O157:H7 and Staphylococcus aureus in tabbouleh salad stored at 21, 10 and 4 °C. Acetic acid was more inhibitory toward S. Typhimurium and E. coli O157:H7 than citric acid at 21 °C; S. Typhimurium and E. coli O157:H7 cells were not detected in tabbouleh treated with 0.4% acetic acid after 5 and 7 days, respectively. The combined effect of acetic and citric acid was synergistic against S. Typhimurium, and E. coli O157:H7, but not against S. aureus. The combinations of acetic and citric acids reduced S. Typhimurium, and E. coli O157:H7 to below the detection levels after 2 and 3 days at 21 °C, respectively. However, these treatments significantly reduced S. aureus numbers compared to the control at tested temperatures by the end of storage. Acetic and citric acids have the potential to be used in tabbouleh salad to reduce the risk from S. Typhimurium, E. coli O157:H7 and S. aureus.

Evaluation of chlorine dioxide, acidified sodium chlorite and peroxyacetic acid for control of Escherichia coli O157:H7 in beef patties from treated beef trim.

The effectiveness of 30 to 400ppm chlorine dioxide (CDO), acidified sodium chlorite (ASC) and peroxyacetic acid (PAA) to control Escherichia coli O157:H7 in beef was examined. Ground beef made from treated meat was vacuum packaged and stored at 4°C for 4d. CDO or ASC concentration by storage time interaction for inactivation of E. coli O157:H7 was significant (P<0.05). Exposure of beef to 200 and 400ppm CDO caused 0.73 and 1.25logcfu/g reduction in the numbers of pathogen, respectively, and an additional 2.08 and 2.25logcfu/g reduction, respectively, occurred at day 4. At 400ppm ASC caused a 0.87logcfu/g reduction and an additional 0.86logcfu/g inactivation at day 4. PAA caused ≤0.8logcfu/g reduction in pathogen numbers at ≤400ppm. Among tested antimicrobials, CDO was most effective and had a positive interaction with cold storage where additional E. coli O157:H7 inactivation occurred.

Emergence of Antibiotic Resistance in Listeria monocytogenes Isolated from Food Products: A Comprehensive Review.

Listeria monocytogenes is an opportunistic pathogen that has been involved in several deadly illness outbreaks. Future outbreaks may be more difficult to manage because of the emergence of antibiotic resistance among L. monocytogenes strains isolated from food products. The present review summarizes the available evidence on the emergence of antibiotic resistance among L. monocytogenes strains isolated from food products and the possible ways this resistance has developed. Furthermore, the resistance of food L. monocytogenes isolates to antibiotics currently used in the treatment of human listeriosis such as penicillin, ampicillin, tetracycline, and gentamicin, has been documented. Acquisition of movable genetic elements is considered the major mechanism of antibiotic resistance development in L. monocytogenes. Efflux pumps have also been linked with resistance of L. monocytogenes to some antibiotics including fluoroquinolones. Some L. monocytogenes strains isolated from food products are intrinsically resistant to several antibiotics. However, factors in food processing chains and environments (from farm to table) including extensive or sub-inhibitory antibiotics use, horizontal gene transfer, exposure to environmental stresses, biofilm formation, and presence of persister cells play crucial roles in the development of antibiotic resistance by L. monocytogenes.

Combination of essential oil compounds and phenolic acids against Escherichia coli O157:H7 in vitro and in dry-fermented sausage production.

Escherichia coli O157:H7 is a foodborne pathogen that causes hemorrhagic colitis and hemolytic uremic syndrome. The low dose of infection and severity of the disease represent a concern to public health. Natural compounds have been widely applied as food additives to replace synthetic preservatives. The aim of this study was to determine the efficiency of essential oil compounds (EOCs) in combination with phenolic acids (PA) in vitro and in dry-fermented sausage production. Minimum Inhibitory Concentration (MIC) and Fractional Inhibitory Concentration index (FICindex) were determined for a 5-strain mixture of E. coli O157:H7. Batches of sausage tainted with E. coli O157:H7 were produced using Pediococcus pentosaceus UM 116P and Staphylococcus carnosus UM 123M as starter cultures. The best combination of EOCs and PAs found in vitro was used as an additive. Chemical-physical and microbiological analyses were evaluated weekly from day 0 to 35 after production. Sensory evaluation (texture, odor, flavor, appearance and overall evaluation) of E. coli-free sausages was conducted using a 9-point hedonic scale with 56 untrained volunteers. The MIC values of allyl isothiocyanate (AITC), carvacrol (CAR), ferulic acid (FA), o-coumaric acid (CA) and p-hydroxybenzoic acid (AHB) were, respectively, 0.25; 1.3; 5.12; 18.27; and 37mM. AITC combined with CA had a synergistic effect (FICindex=0.25) and together they were applied in the production of dry fermented sausage at concentrations of 10× FIC and 20× FIC. Aw had no significant difference among treatments, whereas the pH of 10× FIC and 20× FIC were higher than the control. E. coli O157:H7 was reduced by >5logCFU/g with 20× FIC after 21d, and by 2.8logCFU/g with 10× FIC after 35d. Sensory analysis showed that the combination of AITC and ο-coumaric acid in both treatments presented lower scores in the 5 categories when compared to the control, but none of the parameters received a negative score. This study demonstrated that the combination of AITC and ο-coumaric acid at 20× FIC reduced E. coli O157:H7 in compliance with the North American legislation, but adjustments in the dose are necessary to improve the sensory characteristics of the final product.