Browsing by Author "Meneses, Rui"
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- Comparing growth and survival kinetics of persistent and sporadic strains of listeria monocytogenes from alheira sausagePublication . Meneses, Rui; Pereira, Catarina; Ferreira, Vânia; Magalhães, Rui; Barbosa, Joana; Silva, Beatriz Nunes; Teixeira, PaulaMotivation: L. monocytogenes is known to persist in food processing environments, with some strains being routinely isolated (persistent), while others are only occasionally found (sporadic). This raises the question: Are persistent strains more resistant to stress conditions compared to sporadic strains from similar sources? Objective: To investigate the effect of food processing related stresses (pH=6 and 8% NaCl) on the behaviour of L. monocytogenes isolates from alheira sausage, compared to a set of reference conditions (37 °C, 0% NaCl, pH=7). Results: Compared to the reference conditions: High salinity conditions → significantly longer lag times and lower μmax for all isolates Low pH (pH = 6) reduced μmax but also shortened the lag phase for most isolates These sub-optimal conditions were insufficient to promote pathogen decay The persistent strains #2981 and #3048 do not exhibit a particular behavior nor appear to have increased resistance against the conditions tested This result is aligned with recent research. Conclusions: No significant differences were found between persistent and sporadic strains, suggesting that persistence events may not be explained by a better aptitude for growth. However, further research with a larger number of isolates is needed.
- Depicting the suitability of FTIR to improve the differentiation of persistent and sporadic Listeria monocytogenesPublication . Meneses, Rui; Sousa, Clara; Teixeira, PaulaListeria monocytogenes is a ubiquitous Gram-positive pathogen that is particularly harmful to immunocompromised individuals. In food processing environments (FPEs), certain strains of L. monocytogenes are routinely isolated, while others are only encountered sporadically. One possible explanation for this recurrent isolation correlates with the presence of heterogeneous subpopulations, some of which can withstand adverse conditions encompassing high salinity, low temperature, and low pH, along with other FPEs-related stressors. We set out to evaluate the suitability of Fourier Transformed Infrared Atenuated Total Reflectance (FTIR-ATR) spectroscopy to discriminate between the fitest persistent specimens from the remaining sporadic subpopulations. 72 L. monocytogenes isolates, encompassing both persistent and sporadic L. monocytogenes, were grown in microtiter plates in the presence of different food-associated stressors (pH, T ºC, % NaCl), with growth curves obtained by measuring the optical density (OD600). After reaching the late exponential phase, the cell pellets were collected and analysed by FTIR-ATR spectroscopy. Additionally, infrared (IR) spectra of isolates grown in agar plates at 37ºC were collected. Partial Least-Squares Discriminant Analysis classification models based on collected IR spectra were developed to determine the viability of FTIR spectroscopy to discriminate persistence in different conditions. The gathered data showed no significant differences in growth rates and lag phases of persistent and sporadic L. monocytogenes in a planktonic state when grown at 37ºC or under the food-associated stressors tested. FTIR analysis has shown promising results in differentiating persistent and sporadic isolates belonging to the same serogroup, achieving correct assignment rates of over 70%.
- Differentiation between persistent and sporadic Listeria monocytogenes through growth kineticsPublication . Meneses, Rui; Pereira, Catarina; Barbosa, Joana; Magalhães, Rui; Ferreira, Vânia; Teixeira, Paula
- Differentiation between persistent and sporadic Listeria monocytogenes through growth kineticsPublication . Meneses, Rui; Pereira, Catarina; Barbosa, Joana; Magalhães, Rui; Ferreira, Vânia; Teixeira, Paula
- Marination as a hurdle to microbial pathogens and spoilers in poultry meat products: a brief reviewPublication . Meneses, Rui; Teixeira, PaulaPoultry meat, due to its low price and nutritional value, is a healthy and easily accessible option for many households worldwide. Poultry consumption is, therefore, expected to continue to grow. However, this increase may lead to the rising numbers of cases of bacterial gastroenteritis, as poultry meat often carries foodborne pathogens such as Campylobacter spp. and Salmonella spp. While the current on-farm biosecurity programs and food safety management systems implemented by the poultry industry are intended to mitigate the presence of these pathogens, some find their way to the retail level, posing a risk to the consumer. A safeguard for the consumer could potentially result from meat marination. However, the current marinated meat products sold on the market aim to extend the shelf life and overall taste and tenderness of the meat rather than its safety. Marination could be optimised not only to reduce any foodborne pathogen present in the meat but also to increase the shelf life reducing waste at the retail level. Formulations composed of various ingredients with different active principles may be used to achieve this objective. Wines present a superb component for marinades. Due to their complex nature, wines possess organic acids, phenolic compounds, and ethanol, all of which own significant antimicrobial potential. Essential oils may be another option. By combining different active principles in a marinade, we could potentially reduce the concentrations of the overall bactericidal ingredients. The objective of this review was to analyse the recent studies in this field and try to understand the best options for developing a convenient, natural-based bactericidal marinade.