Browsing by Author "Ezzaky, Youssef"
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- Controlling Listeria monocytogenes contamination in fresh goat milk cheeses: Dynamic modelling during storagePublication . Bonilla-Luque, Olga María; Possas, Arícia; Gonzales-Barron, Ursula; Cadavez, Vasco; Ezzaky, Youssef; Hussein, Abdelraheem; Valero, AntonioPredictive models applied for artisanal fresh goat cheeses are invaluable tools for rapid decision-making in quality and safety management. Listeria monocytogenes is a common foodborne pathogen associated with recent safety alerts in ready-to-eat (RTE) products in Andalucia. Managing artisanal production variables, such as storage conditions and final product features (pH or water activity [aw]) might be crucial for controlling L. monocytogenes in these traditional products. This study evaluated the time-temperature dependence of L. monocytogenes during shelf-life of fresh goat milk cheese artisanally produced in Andalucía. The effect of storage temperature (4–25 ◦C) over 5–20 days was tested in lab-scale fresh goat milk cheeses initially inoculated with a three-strain cocktail of the pathogen (ca. 2–3 log cfu/g). The Huang (model A) and Baranyi (model B) models coupled with Ratkowsky were fitted to the collected growth data to describe the relationship between L. monocytogenes concentration, growth rate (μmax, log cfu/d), storage temperature, and time. The results highlighted the higher variability of growth data at 4 ◦C, the linear relationship between μmax and temperature, the inverse correlation between ymax (exceeding 5 log cfu/g at all the temperatures) and ΔY (with a maximum of 4.386 and minimum of 2.461, at 4 and 25 ◦C, respectively) and a faster decrease of pH at higher temperatures. Model validity, assessed through goodness-of-fit and both internal and external validations (under both isothermal temperatures and a dynamic temperature workflow simulating real production scenario), revealed good model adjustment to L. monocytogenes growth in artisanal commercial cheeses, after determining a correction factor of 1.806 and 1.856, for models A and B, respectively. Predictions indicated that an initially contaminated artisanal fresh goat milk cheese would not meet regulatory limits after 4 days under refrigeration conditions (4 ◦C), aerobic conditions, or opened packaging. These results highlight the potential public health risk of artisanal fresh goat milk cheeses related to L. monocytogenes transmission if manufacturing and storage conditions are not well controlled, emphasizing the need for stringent microbial control efforts and mitigation measures.
- In vitro antimicrobial activity of extracts and essential oils of Cinnamomum, Salvia, and Menthaspp. against foodborne pathogens: a meta‐analysis studyPublication . Ezzaky, Youssef; Elmoslih, Abdelkhaleq; Silva, Beatriz Nunes; Bonilla‐Luque, Olga María; Possas, Arícia; Valero, Antonio; Cadavez, Vasco; Gonzales-Barron, Ursula; Achemchem, FouadEssential oils (EOs) are a class of natural products that exhibit potent antimicrobial properties against a broad spectrum of bacteria. Inhibition diameters (IDs) and minimum inhibitory concentrations (MICs) are the typical measures of antimicrobial activity for extracts and EOs obtained from Cinnamomum, Salvia, and Mentha species. This study used a meta-analytical regression analysis to investigate the correlation between ID and MIC measurements and the variability in antimicrobial susceptibility tests. By utilizing pooled ID models, this study revealed significant differences in foodborne pathogens’ susceptibility to extracts, which were dependent on both the plant species and the methodology employed (p < .05). Cassia showed the highest efficacy against Salmonella spp., exhibiting a pooled ID of 26.24 mm, while cinnamon demonstrated the highest efficacy against Bacillus cereus, with a pooled ID of 23.35 mm. Mint extract showed the greatest efficacy against Escherichia coli and Staphylococcus aureus. Interestingly, cinnamon extract demonstrated the lowest effect against Shiga toxin-producing E. coli, with a pooled ID of only 8.07 mm, whereas its EOs were the most effective against this bacterial strain. The study found that plant species influenced the MIC, while the methodology did not affect MIC measurements (p > .05). An inverse correlation between ID and MIC measurements was identified (p < .0001). These findings suggest that extracts and EOs obtained from Cinnamomum, Salvia, and Mentha spp. have the potential to inhibit bacterial growth. The study highlights the importance of considering various factors that may influence ID and MIC measurements when assessing the effectiveness of antimicrobial agents.
- In vitro antimicrobial activity of extracts and essential oils of Cinnamomum, Salvia, and Menthaspp. against foodborne pathogens: a meta‐analysis studyPublication . Ezzaky, Youssef; Elmoslih, Abdelkhaleq; Silva, Beatriz Nunes; Bonilla‐Luque, Olga M.; Possas, Arícia; Valero, Antonio; Cadavez, Vasco; Gonzales-Barron, Ursula; Achemchem, FouadGenetic analysis of the honey bee spermathecal content can be particularly useful to provide an estimate of the genetic diversity and purity of the surrounding populations. Here we compared the concentration and quality of DNA extracted from queen spermatheca using four commercial kits to determine the best method to obtain DNA suitable for single nucleotide polymorphism genotyping by next-generation sequencing. The four kits were tested with different adjustments in the lysis incubation time, use of RNA-carrier, elution conditions and number of re-elutions. Only the use of QIAamp DNA Microkit with 3 h of lysis incubation, the addition of RNA-carrier and multiple re-elutions produced a DNA concentration over the required threshold.
- Meta-analysis of antimicrobial activity of Allium, Ocimum, and Thymus spp. confirms their promising application for increasing food safetyPublication . Bonilla-Luque, Olga María; Silva, Beatriz Nunes; Ezzaky, Youssef; Possas, Arícia; Achemchem, Fouad; Cadavez, Vasco; Gonzales-Barron, Ursula; Valero, AntonioBiopreservation strategies such as the use of Mediterranean plant extracts to ensure food safety are promising to deal with the emergence of antimicrobial resistances and the overreliance on food chemical additives. In the last few decades, antimicrobial susceptibility testing (AST) for evaluating the in vitro antibacterial potential of plant extracts against the most relevant foodborne pathogens has been widely reported in the literature. The current meta-analysis aimed to summarise and analyse the extensive evidence available in the literature regarding the in vitro antimicrobial capability of Allium, Ocimum and Thymus spp. extracts against foodborne pathogens. A systematic review was carried out to gather data on AST results of these extracts against Listeria monocytogenes, Staphylococcus aureus, Salmonella spp., Escherichia coli and Bacillus cereus, including inhibition diameters (ID) and minimum inhibitory concentrations (MIC). A total of 742 records were gathered from a raw collection of 2,065 articles. Weighted mixed-effect linear models were adjusted to data to obtain pooled ID, pooled MIC and the relationship between both model estimations and observations. The pooled results revealed B. cereus as the most susceptible bacteria to Allium sativum (pooled ID = 20.64 ± 0.61 mm) by diffusion methods and S. aureus (pooled MIC = 0.146 mg/mL) by dilution methods. Diffusion methods did not yield conclusive results for Ocimum spp. extracts; however, the lowest pooled MIC was obtained for S. aureus (0.263 mg/mL). Among the foodborne pathogens evaluated, B. cereus showed the highest sensitivity to Thymus spp. extracts by both diffusion and dilution methods (pooled ID = 28.90 ± 2.34 mm and MIC = 0.075 mg/mL). The methodology used for plant extraction was found to not significantly affect MIC values (p > 0.05). Overall, the antimicrobial effectiveness of the studied extracts against Gram-positive and Gram-negative bacteria was demonstrated. Finally, the robustness of the meta-regression model was confirmed, also revealing an inversely proportional correlation between the ID and MIC measurements (p < 0.0001). These results provide a robust scientific basis on the factors affecting the in vitro antimicrobial efficacy of extracts from Mediterranean plants. They also provide valuable information for stakeholders involved in their industrial application in food, including producers, regulatory agencies and consumers which demand green-labelled foods.
- Meta-analysis of in vitro antimicrobial capacity of extracts and essential oils of Syzygium aromaticum, Citrus L. and Origanum L.: contrasting the results of different antimicrobial susceptibility methodsPublication . Silva, Beatriz Nunes; Bonilla-Luque, Olga María; Possas, Arícia; Ezzaky, Youssef; Elmoslih, Abdelkhaleq; Teixeira, José António; Achemchem, Fouad; Valero, Antonio; Cadavez, Vasco; Gonzales-Barron, UrsulaDiffusion methods, including agar disk-diffusion and agar well-diffusion, as well as dilution methods such as broth and agar dilution, are frequently employed to evaluate the antimicrobial capacity of extracts and essential oils (EOs) derived from Origanum L., Syzygium aromaticum, and Citrus L. The results are reported as inhibition diameters (IDs) and minimum inhibitory concentrations (MICs), respectively. In order to investigate potential sources of variability in antimicrobial susceptibility testing results and to assess whether a correlation exists between ID and MIC measurements, meta-analytical regression models were built using in vitro data obtained through a systematic literature search. The pooled ID models revealed varied bacterial susceptibilities to the extracts and in some cases, the plant species and methodology utilised impacted the measurements obtained (p < 0.05). Lemon and orange extracts were found to be most effective against E. coli (24.4 ± 1.21 and 16.5 ± 0.84 mm, respectively), while oregano extracts exhibited the highest level of effectiveness against B. cereus (22.3 ± 1.73 mm). Clove extracts were observed to be most effective against B. cereus and demonstrated the general trend that the well-diffusion method tends to produce higher ID (20.5 ± 1.36 mm) than the disk-diffusion method (16.3 ± 1.40 mm). Although the plant species had an impact on MIC, there is no evidence to suggest that the methodology employed had an effect on MIC (p > 0.05). The ID–MIC model revealed an inverse correlation (R2 = 47.7%) and highlighted the fact that the extract dose highly modulated the relationship (p < 0.0001). The findings of this study encourage the use of extracts and EOs derived from Origanum, Syzygium aromaticum, and Citrus to prevent bacterial growth. Additionally, this study underscores several variables that can impact ID and MIC measurements and expose the correlation between the two types of results.