Vânia Ferreira - Academia.edu (original) (raw)
Papers by Vânia Ferreira
Listeria Monocytogenes
Listeria monocytogenes is a foodborne pathogen, which causes listeriosis disease among humans and... more Listeria monocytogenes is a foodborne pathogen, which causes listeriosis disease among humans and other animal species. Infections in humans mainly occur in immunocompromised individuals and are caused by the consumption of ready-to-eat and raw food products contaminated with the pathogen. To ensure survival in nature, L. monocytogenes easily adapts to different environmental conditions, and that justifies the hurdles to prevent bacterial growth inside the food chain. Exposure to a single or multiple sublethal stresses, as those impaired by food processing, food matrices, and the gastrointestinal tract, can enhance tolerance of L. monocytogenes to stresses and increase its survival and pathogenesis. This chapter summarizes the current information on the adaptive response of L. monocytogenes to different stresses, namely (1) cold stress, (2) acid stress, (3) osmotic stress, (4) desiccation stress, and (5) high hydrostatic pressure, and the impact of these stresses on L. monocytogenes virulence. The objective is to provide the background information that is necessary for the development of scientifically sound control strategies to improve food safety and to reduce the uncertainty of microbial risk assessments, associated to limited knowledge on the behavior of cells capable to adapt and survive stresses.
Applied Sciences
The monitoring of the microbial quality of fresh products in the industrial environment has mainl... more The monitoring of the microbial quality of fresh products in the industrial environment has mainly focused on bacterial indicators. Protozoa, such as Giardia duodenalis, Cryptosporidium spp., Toxoplasma gondii, and Cyclospora cayetanensis, are routinely excluded from detection and surveillance systems, despite guidelines and regulations that support the need for tracking and monitoring these pathogens in fresh food products. Previous studies performed by our laboratory, within the scope of the SafeConsume project, clearly indicated that consumption of fresh produce may be a source of T. gondii, thus posing a risk for the contraction of toxoplasmosis for susceptible consumers. Therefore, preliminary work was performed in order to assess the microbiological quality of vegetables, highlighting not only bacteria (Escherichia. coli, Listeria monocytogenes, and Salmonella spp.), but also the zoonotic protozoa G. duodenalis and Cryptosporidium spp. Although all samples were found to be acc...
Foods
Campylobacter is the leading bacterial cause of diarrheal disease worldwide and poultry remains t... more Campylobacter is the leading bacterial cause of diarrheal disease worldwide and poultry remains the primary vehicle of its transmission to humans. Due to the rapid increase in antibiotic resistance among Campylobacter strains, the World Health Organization (WHO) added Campylobacter fluoroquinolone resistance to the WHO list of antibiotic-resistant “priority pathogens”. This study aimed to investigate the occurrence and antibiotic resistance of Campylobacter spp. in meat samples from chickens reared in different production systems: (a) conventional, (b) free-range and (c) backyard farming. Campylobacter spp. was detected in all samples from conventionally reared and free-range broilers and in 72.7% of backyard chicken samples. Levels of contamination were on average 2.7 × 103 colony forming units (CFU)/g, 4.4 × 102 CFU/g and 4.2 × 104 CFU/g in conventionally reared, free-range and backyard chickens, respectively. Campylobacter jejuni and Campylobacter coli were the only species isola...
Water, 2022
Water contaminated with microbiological and chemical constituents can cause a variety of diseases... more Water contaminated with microbiological and chemical constituents can cause a variety of diseases. Water bodies may become contaminated by wild and domestic animal feces, agricultural runoff or sewage, and are often overlooked as a reservoir and source of human infection by pathogenic microorganisms. The objectives of this study were to evaluate the presence of the zoonotic pathogens, Salmonella spp. and Listeria monocytogenes, in various water bodies located in urban and rural areas in the north of Portugal. Water samples were collected from six sites, including natural and artificial ponds, in two different time periods. Several water quality physicochemical parameters, as well as fecal indicator bacteria, were evaluated. High levels of total coliforms (>1.78 log CFU/100 mL) were detected in all samples, and substantial numbers of Enterococcus (>2.32 log CFU/100 mL) were detected in two ponds located in a city park and in an urban garden. Escherichia coli counts ranged from ...
International Journal of Food Microbiology, 2021
Cross-contamination events of Campylobacter spp. in domestic kitchens associated with consumer ha... more Cross-contamination events of Campylobacter spp. in domestic kitchens associated with consumer handling practices of raw poultry
International Journal of Food Microbiology, 2021
About 40% of foodborne infections are acquired in the home. The aim of the present study was to t... more About 40% of foodborne infections are acquired in the home. The aim of the present study was to track contamination of pathogens during domestic food preparation and link the contamination to preparation practices. Research participants from 87 households in six European countries were observed and interviewed during shopping and preparation of a chicken and vegetable meal. The presence of Salmonella spp., Campylobacter spp. and norovirus on raw chicken, kitchen surfaces, cloths and sponges was determined. The prevalence of Campylobacter on raw chicken varied from 8.3% in Norway (NO) to 80% in France (FR) and Portugal (PT), with a mean prevalence of 57%. Campylobacter was found on half of the products that had been frozen and appeared to be less prevalent on chicken from supermarkets than other sources. Salmonella was found in 8.6% of raw chicken samples, exclusively from Hungary (HU). A relationship between observed practices and spread of pathogens to kitchen surfaces was found only for the use of cutting boards for chicken and/or vegetables. After food preparation, Campylobacter and Salmonella were isolated from 23% (samples derived from HU, RO, UK) and 8.7% (HU), respectively of cutting boards. Research participants in France and Portugal were more likely to buy products that fitted their recipe, with less need for using cutting boards. Using the same board and knife for vegetables after using it for chicken and without washing with detergent was common in Portugal and Romania, but not in the other countries. Contamination with Campylobacter to other kitchen surfaces or washing utensils were found in five households (UK, RO, PT). Rinsing chicken in sinks was common in three countries (PT, HU, RO), and washing vegetables in the same sink was also usual. Prevalence of Norovirus was low, with detection in one out of 451 samples. The participants' awareness of the risk posed by pathogens from raw chicken differed among the six countries, with higher awareness in Norway and the UK than the other countries studied. In conclusion, practices intended to avoid cross-contamination from chicken to kitchen surfaces and washing utensils are not established among consumers in all European countries. Nevertheless, cross-contamination events that disseminate infectious doses of pathogens seems to be rare, probably due to the relatively low levels of pathogens in food combined with food preferences. Food safety interventions must consider the national food culture, preferences, practices and the prevalence and levels of pathogens in food. Emphasis should be on
PLOS ONE, 2021
Campylobacter spp. are the most common bacterial pathogens associated with human gastroenteritis ... more Campylobacter spp. are the most common bacterial pathogens associated with human gastroenteritis in industrialized countries. Contaminated chicken is the food vehicle associated with the majority of reported cases of campylobacteriosis, either by the consumption of undercooked meat or via cross- contamination of ready-to-eat (RTE) foods during the handling of contaminated raw chicken parts and carcasses. Our results indicate that cooking salt (used for seasoning) is a potential vehicle for Campylobacter spp. cross-contamination from raw chicken to lettuce, through unwashed hands after handling contaminated chicken. Cross-contamination events were observed even when the chicken skin was contaminated with low levels of Campylobacter spp. (ca. 1.48 Log CFU/g). The pathogen was recovered from seasoned lettuce samples when raw chicken was contaminated with levels ≥ 2.34 Log CFU/g. We also demonstrated that, once introduced into cooking salt, Campylobacter spp. are able to survive in a cu...
Comprehensive Reviews in Food Science and Food Safety, 2021
Nontyphoidal salmonellae are among the most prevalent foodborne pathogens causing gastrointestina... more Nontyphoidal salmonellae are among the most prevalent foodborne pathogens causing gastrointestinal infections worldwide. A high number of cases and outbreaks of salmonellosis are associated with the consumption of eggs and egg products, and several of these occur at the household level. The aim of the current study is to critically evaluate the current status of knowledge on Salmonella in eggs from a consumer's perspective, analyzing the hazard occurrence and the good practices that should be applied to reduce salmonellosis risk. Following a HACCP (Hazard Analysis and Critical Control Point) based approach, some steps along the food journey were identified as Critical Consumer Handling (CCH)-steps in which consumers, through their behavior or choice, can significantly reduce the level of Salmonella in eggs and egg products. From shopping/collecting to consumption, each of these steps is discussed in this review to provide an evidence-based overview of risk factors of human salmonellosis related to egg consumption. The main message to consumers is to choose Salmonella-free eggs (those that some official entity or producer guarantees that does not contain Salmonella), when available, especially for dishes that are not fully heat treated. Second, as guaranteed Salmonella-free eggs are only available in a few countries, refrigerated storage from the point of collection and proper cooking will significantly reduce the risk of salmonellosis. This will require a revision of the actual recommendations/regulations, as not all ensure that eggs are maintained at temperatures that prevent growth of Salmonella from collection until the time of purchasing. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Foods, 2020
In addition to environmental pollution issues, social concerns about the sustainability, safety, ... more In addition to environmental pollution issues, social concerns about the sustainability, safety, and quality of conventionally grown fruits and vegetables have been increasing. In order to evaluate if there were any microbiological differences between samples of organic and conventional lettuce, a wide range of parameters were tested, including pathogens and indicator organisms: the enumeration of Escherichia coli; the detection of Salmonella spp.; the detection/enumeration of Listeria monocytogenes; the enumeration of lactic acid bacteria, Pseudomonas spp. yeasts and molds, and Enterobacteriaceae. This study also evaluated the chemical safety of the lettuce samples, quantifying the nitrate concentration and 20 pesticides (14 organochlorine and 6 organophosphorus pesticides). Significant differences (p < 0.05) between the conventional and organic samples were only detected for the counts of total microorganisms at 30 °C. Pathogens were absent in all the samples. The analytical me...
Food Control, 2019
Cleaning is a method at the disposal of domestic cooks for curtailing the dispersal of foodborne ... more Cleaning is a method at the disposal of domestic cooks for curtailing the dispersal of foodborne pathogens in the process of preparing food. The observation of visible dirt/soil 'in the wrong place' operates as one of the stimuli for action. This paper makes a transdisciplinary contribution to understandings of cleaning as a practice for ensuring safety in the kitchen, and it is mainly focused on the (in)visibility of soil or dirt. The social science research included analysis of a consumer survey in 10 European countries where 9966 respondents were asked about motivations for cleaning in the kitchen. This paper draws also on three microbiological tests. First, Portuguese (n = 7) and Norwegian (6) consumers evaluated the visible cleanliness of 10 surface areas in their kitchens, directly and through the visible residue and total bacterial numbers accumulated on a white cotton swab after swabbing the surface areas. Secondly, 15 Norwegian consumers tested if they could visually detect different types of food soils, as these dried on kitchen surfaces. Finally, the survival of Campylobacter and Salmonella in the same soil types was tested under lab conditions as the soil dried out. Cleaning food preparation surfaces "after food preparation" (73%), "before preparing food" (53%) and "when they are dirty" (43%) were the three most common self-reported behaviours. Routine was the most common motivation to clean, but this was age dependent. There was low correlation between visual detection of dirt/soil and bacterial enumeration. Visual detection of soils was dependent on type and concentration of food soils and material of the surface; the soils were more easily detected on laminate surfaces than plastic and wood. Campylobacter died rapidly, while Salmonella survived for at least one week in food soils drying on a countertop laminate surface. Presence of food soils in concentrations that can be detected visually, protected Salmonella against drying. In conclusion, selecting materials where soil/dirt can easily be detected visually in the kitchen surfaces, may motivate consumers to clean and will reduce risk, but establishing a habit to clean surfaces soon after food preparation is also important from a food safety perspective.
Food microbiology, 2018
The application of lytic phages as biocontrol agents is emerging as a promising strategy towards ... more The application of lytic phages as biocontrol agents is emerging as a promising strategy towards elimination or reduction of foodborne pathogens in a variety of food products. This technology is particularly advantageous for minimally processed and ready-to-eat (RTE) foods. In this study, the potential use of Listex™ P100 combined with high hydrostatic pressure (HPP), to enhance the control of Listeria monocytogenes in food was evaluated. For that, the effect of three pressures (200, 300 or 400 MPa; 5 min, 10 °C) on phage P100 stability was tested when inoculated in six different matrices: phosphate buffered saline (PBS, pH 7.4); apple juice (pH 3.41); orange/carrot nectar (pH 3.54); UHT whole milk (pH 6.73); and, two traditional Portuguese fermented products, "Serra da Estrela" cheese (pH 5.66) and "Alheira", a meat sausage (pH 6.07). The results showed that treatment at 400 MPa reduced phage titres to below the detection level in all matrices, whereas at milder...
Eurosurveillance, 2015
In Portugal, listeriosis has been notifiable since April 2014, but there is no active surveillanc... more In Portugal, listeriosis has been notifiable since April 2014, but there is no active surveillance programme for the disease. A retrospective study involving 25 national hospitals led to the detection of an outbreak that occurred between March 2009 and February 2012. The amount of time between the start of the outbreak and its detection was 16 months. Of the 30 cases of listeriosis reported, 27 were in the Lisbon and Vale do Tejo region. Two cases were maternal/neonatal infections and one resulted in fetal loss. The mean age of the non-maternal/neonatal cases was 59 years (standard deviation: 17); 13 cases were more than 65 years-old. The case fatality rate was 36.7%. All cases were caused by molecular serogroup IVb isolates indistinguishable by pulsed-field gel electrophoresis and ribotype profiles. Collaborative investigations with the national health and food safety authorities identified cheese as the probable source of infection, traced to a processing plant. The magnitude of t...
Microorganisms in Industry and Environment - From Scientific and Industrial Research to Consumer Products - Proceedings of the III International Conference on Environmental, Industrial and Applied Microbiology (BioMicroWorld2009), 2010
Healthy adults and children occasionally get infected with Listeria, but they rarely become serio... more Healthy adults and children occasionally get infected with Listeria, but they rarely become seriously ill.
Objective. A total of 725 Listeria monocytogenes isolates, 607 from various foods and 118 from cl... more Objective. A total of 725 Listeria monocytogenes isolates, 607 from various foods and 118 from clinical cases of listeriosis, were investigated concerning their ability to form biofilms, at 4 ∘ C during 5 days and at 37 ∘ C during 24 h. Methods. Biofilm production was carried out on polystyrene tissue culture plates. Five L. monocytogenes isolates were tested for biofilm formation after being exposed to acidic and osmotic stress conditions. Results. Significant differences (< 0.01) between clinical and food isolates were observed. At 37 ∘ C for 24 h, most food isolates were classified as weak or moderate biofilm formers whereas all the clinical isolates were biofilm producers, although the majority were weak. At 4 ∘ C during 5 days, 65 and 59% isolates, from food and clinical cases, respectively, were classified as weak. After both sublethal stresses, at 37 ∘ C just one of the five isolates tested was shown to be more sensitive to subsequent acidic exposure. However, at 4 ∘ C both stresses did not confer either sensitivity or resistance. Conclusions. Significant differences between isolates origin, temperature, and sublethal acidic stress were observed concerning the ability to form biofilms. Strain, origin, and environmental conditions can determine the level of biofilm production by L. monocytogenes isolates.
Journal of Food Protection, 2014
Over the last 10 to 15 years, increasing evidence suggests that persistence of Listeria monocytog... more Over the last 10 to 15 years, increasing evidence suggests that persistence of Listeria monocytogenes in food processing plants for years or even decades is an important factor in the transmission of this foodborne pathogen and the root cause of a number of human listeriosis outbreaks. L. monocytogenes persistence in other food-associated environments (e.g., farms and retail establishments) may also contribute to food contamination and transmission of the pathogen to humans. Although L. monocytogenes persistence is typically identified through isolation of a specific molecular subtype from samples collected in a given environment over time, formal (statistical) criteria for identification of persistence are undefined. Environmental factors (e.g., facilities and equipment that are difficult to clean) have been identified as key contributors to persistence; however, the mechanisms are less well understood. Although some researchers have reported that persistent strains possess specifi...
Foodborne Pathogens and Disease, 2013
The aim of this study was to characterize a broad collection of isolates of Listeria monocytogene... more The aim of this study was to characterize a broad collection of isolates of Listeria monocytogenes, of different serotypes, recovered in Portugal between 2003 and 2007 from foods (n=353) and from clinical cases of human listeriosis (n=95), in terms of antimicrobial susceptibility. All the isolates were susceptible to ampicillin, the preferred agent to treat listeriosis. Resistances to nitrofurantoin (n=99), to ciprofloxacin (n=18), to erythromycin (n=10), to tetracycline (n=2), to gentamicin (n=1) and to rifampicin (n=1) were observed. One hundred (28.3%) and 20 (21.0%) food and clinical isolates, respectively, were resistant to at least one antibiotic. Eight isolates (1.8%) were resistant to two or more antimicrobials of different classes, and all were collected from foods. Serogroup IVb included the highest percentage of isolates resistant to erythromycin. The highest percentages of isolates resistant to nitrofurantoin were of serogroup IVb and IIc. It was demonstrated that the incidence of antibiotic-resistant isolates of L. monocytogenes, during the period 2003 to 2007, was low in Portugal but still higher than that observed in other countries. Given the increasing population at greater risk of listeriosis, namely, the elderly, the high mortality rate of the infection and the detection of resistant isolates, monitoring for antibiotic resistance in strains of L. monocytogenes on a large scale, and assessing the risk of infection by these strains, is highly recommended.
Listeria Monocytogenes
Listeria monocytogenes is a foodborne pathogen, which causes listeriosis disease among humans and... more Listeria monocytogenes is a foodborne pathogen, which causes listeriosis disease among humans and other animal species. Infections in humans mainly occur in immunocompromised individuals and are caused by the consumption of ready-to-eat and raw food products contaminated with the pathogen. To ensure survival in nature, L. monocytogenes easily adapts to different environmental conditions, and that justifies the hurdles to prevent bacterial growth inside the food chain. Exposure to a single or multiple sublethal stresses, as those impaired by food processing, food matrices, and the gastrointestinal tract, can enhance tolerance of L. monocytogenes to stresses and increase its survival and pathogenesis. This chapter summarizes the current information on the adaptive response of L. monocytogenes to different stresses, namely (1) cold stress, (2) acid stress, (3) osmotic stress, (4) desiccation stress, and (5) high hydrostatic pressure, and the impact of these stresses on L. monocytogenes virulence. The objective is to provide the background information that is necessary for the development of scientifically sound control strategies to improve food safety and to reduce the uncertainty of microbial risk assessments, associated to limited knowledge on the behavior of cells capable to adapt and survive stresses.
Applied Sciences
The monitoring of the microbial quality of fresh products in the industrial environment has mainl... more The monitoring of the microbial quality of fresh products in the industrial environment has mainly focused on bacterial indicators. Protozoa, such as Giardia duodenalis, Cryptosporidium spp., Toxoplasma gondii, and Cyclospora cayetanensis, are routinely excluded from detection and surveillance systems, despite guidelines and regulations that support the need for tracking and monitoring these pathogens in fresh food products. Previous studies performed by our laboratory, within the scope of the SafeConsume project, clearly indicated that consumption of fresh produce may be a source of T. gondii, thus posing a risk for the contraction of toxoplasmosis for susceptible consumers. Therefore, preliminary work was performed in order to assess the microbiological quality of vegetables, highlighting not only bacteria (Escherichia. coli, Listeria monocytogenes, and Salmonella spp.), but also the zoonotic protozoa G. duodenalis and Cryptosporidium spp. Although all samples were found to be acc...
Foods
Campylobacter is the leading bacterial cause of diarrheal disease worldwide and poultry remains t... more Campylobacter is the leading bacterial cause of diarrheal disease worldwide and poultry remains the primary vehicle of its transmission to humans. Due to the rapid increase in antibiotic resistance among Campylobacter strains, the World Health Organization (WHO) added Campylobacter fluoroquinolone resistance to the WHO list of antibiotic-resistant “priority pathogens”. This study aimed to investigate the occurrence and antibiotic resistance of Campylobacter spp. in meat samples from chickens reared in different production systems: (a) conventional, (b) free-range and (c) backyard farming. Campylobacter spp. was detected in all samples from conventionally reared and free-range broilers and in 72.7% of backyard chicken samples. Levels of contamination were on average 2.7 × 103 colony forming units (CFU)/g, 4.4 × 102 CFU/g and 4.2 × 104 CFU/g in conventionally reared, free-range and backyard chickens, respectively. Campylobacter jejuni and Campylobacter coli were the only species isola...
Water, 2022
Water contaminated with microbiological and chemical constituents can cause a variety of diseases... more Water contaminated with microbiological and chemical constituents can cause a variety of diseases. Water bodies may become contaminated by wild and domestic animal feces, agricultural runoff or sewage, and are often overlooked as a reservoir and source of human infection by pathogenic microorganisms. The objectives of this study were to evaluate the presence of the zoonotic pathogens, Salmonella spp. and Listeria monocytogenes, in various water bodies located in urban and rural areas in the north of Portugal. Water samples were collected from six sites, including natural and artificial ponds, in two different time periods. Several water quality physicochemical parameters, as well as fecal indicator bacteria, were evaluated. High levels of total coliforms (>1.78 log CFU/100 mL) were detected in all samples, and substantial numbers of Enterococcus (>2.32 log CFU/100 mL) were detected in two ponds located in a city park and in an urban garden. Escherichia coli counts ranged from ...
International Journal of Food Microbiology, 2021
Cross-contamination events of Campylobacter spp. in domestic kitchens associated with consumer ha... more Cross-contamination events of Campylobacter spp. in domestic kitchens associated with consumer handling practices of raw poultry
International Journal of Food Microbiology, 2021
About 40% of foodborne infections are acquired in the home. The aim of the present study was to t... more About 40% of foodborne infections are acquired in the home. The aim of the present study was to track contamination of pathogens during domestic food preparation and link the contamination to preparation practices. Research participants from 87 households in six European countries were observed and interviewed during shopping and preparation of a chicken and vegetable meal. The presence of Salmonella spp., Campylobacter spp. and norovirus on raw chicken, kitchen surfaces, cloths and sponges was determined. The prevalence of Campylobacter on raw chicken varied from 8.3% in Norway (NO) to 80% in France (FR) and Portugal (PT), with a mean prevalence of 57%. Campylobacter was found on half of the products that had been frozen and appeared to be less prevalent on chicken from supermarkets than other sources. Salmonella was found in 8.6% of raw chicken samples, exclusively from Hungary (HU). A relationship between observed practices and spread of pathogens to kitchen surfaces was found only for the use of cutting boards for chicken and/or vegetables. After food preparation, Campylobacter and Salmonella were isolated from 23% (samples derived from HU, RO, UK) and 8.7% (HU), respectively of cutting boards. Research participants in France and Portugal were more likely to buy products that fitted their recipe, with less need for using cutting boards. Using the same board and knife for vegetables after using it for chicken and without washing with detergent was common in Portugal and Romania, but not in the other countries. Contamination with Campylobacter to other kitchen surfaces or washing utensils were found in five households (UK, RO, PT). Rinsing chicken in sinks was common in three countries (PT, HU, RO), and washing vegetables in the same sink was also usual. Prevalence of Norovirus was low, with detection in one out of 451 samples. The participants' awareness of the risk posed by pathogens from raw chicken differed among the six countries, with higher awareness in Norway and the UK than the other countries studied. In conclusion, practices intended to avoid cross-contamination from chicken to kitchen surfaces and washing utensils are not established among consumers in all European countries. Nevertheless, cross-contamination events that disseminate infectious doses of pathogens seems to be rare, probably due to the relatively low levels of pathogens in food combined with food preferences. Food safety interventions must consider the national food culture, preferences, practices and the prevalence and levels of pathogens in food. Emphasis should be on
PLOS ONE, 2021
Campylobacter spp. are the most common bacterial pathogens associated with human gastroenteritis ... more Campylobacter spp. are the most common bacterial pathogens associated with human gastroenteritis in industrialized countries. Contaminated chicken is the food vehicle associated with the majority of reported cases of campylobacteriosis, either by the consumption of undercooked meat or via cross- contamination of ready-to-eat (RTE) foods during the handling of contaminated raw chicken parts and carcasses. Our results indicate that cooking salt (used for seasoning) is a potential vehicle for Campylobacter spp. cross-contamination from raw chicken to lettuce, through unwashed hands after handling contaminated chicken. Cross-contamination events were observed even when the chicken skin was contaminated with low levels of Campylobacter spp. (ca. 1.48 Log CFU/g). The pathogen was recovered from seasoned lettuce samples when raw chicken was contaminated with levels ≥ 2.34 Log CFU/g. We also demonstrated that, once introduced into cooking salt, Campylobacter spp. are able to survive in a cu...
Comprehensive Reviews in Food Science and Food Safety, 2021
Nontyphoidal salmonellae are among the most prevalent foodborne pathogens causing gastrointestina... more Nontyphoidal salmonellae are among the most prevalent foodborne pathogens causing gastrointestinal infections worldwide. A high number of cases and outbreaks of salmonellosis are associated with the consumption of eggs and egg products, and several of these occur at the household level. The aim of the current study is to critically evaluate the current status of knowledge on Salmonella in eggs from a consumer's perspective, analyzing the hazard occurrence and the good practices that should be applied to reduce salmonellosis risk. Following a HACCP (Hazard Analysis and Critical Control Point) based approach, some steps along the food journey were identified as Critical Consumer Handling (CCH)-steps in which consumers, through their behavior or choice, can significantly reduce the level of Salmonella in eggs and egg products. From shopping/collecting to consumption, each of these steps is discussed in this review to provide an evidence-based overview of risk factors of human salmonellosis related to egg consumption. The main message to consumers is to choose Salmonella-free eggs (those that some official entity or producer guarantees that does not contain Salmonella), when available, especially for dishes that are not fully heat treated. Second, as guaranteed Salmonella-free eggs are only available in a few countries, refrigerated storage from the point of collection and proper cooking will significantly reduce the risk of salmonellosis. This will require a revision of the actual recommendations/regulations, as not all ensure that eggs are maintained at temperatures that prevent growth of Salmonella from collection until the time of purchasing. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Foods, 2020
In addition to environmental pollution issues, social concerns about the sustainability, safety, ... more In addition to environmental pollution issues, social concerns about the sustainability, safety, and quality of conventionally grown fruits and vegetables have been increasing. In order to evaluate if there were any microbiological differences between samples of organic and conventional lettuce, a wide range of parameters were tested, including pathogens and indicator organisms: the enumeration of Escherichia coli; the detection of Salmonella spp.; the detection/enumeration of Listeria monocytogenes; the enumeration of lactic acid bacteria, Pseudomonas spp. yeasts and molds, and Enterobacteriaceae. This study also evaluated the chemical safety of the lettuce samples, quantifying the nitrate concentration and 20 pesticides (14 organochlorine and 6 organophosphorus pesticides). Significant differences (p < 0.05) between the conventional and organic samples were only detected for the counts of total microorganisms at 30 °C. Pathogens were absent in all the samples. The analytical me...
Food Control, 2019
Cleaning is a method at the disposal of domestic cooks for curtailing the dispersal of foodborne ... more Cleaning is a method at the disposal of domestic cooks for curtailing the dispersal of foodborne pathogens in the process of preparing food. The observation of visible dirt/soil 'in the wrong place' operates as one of the stimuli for action. This paper makes a transdisciplinary contribution to understandings of cleaning as a practice for ensuring safety in the kitchen, and it is mainly focused on the (in)visibility of soil or dirt. The social science research included analysis of a consumer survey in 10 European countries where 9966 respondents were asked about motivations for cleaning in the kitchen. This paper draws also on three microbiological tests. First, Portuguese (n = 7) and Norwegian (6) consumers evaluated the visible cleanliness of 10 surface areas in their kitchens, directly and through the visible residue and total bacterial numbers accumulated on a white cotton swab after swabbing the surface areas. Secondly, 15 Norwegian consumers tested if they could visually detect different types of food soils, as these dried on kitchen surfaces. Finally, the survival of Campylobacter and Salmonella in the same soil types was tested under lab conditions as the soil dried out. Cleaning food preparation surfaces "after food preparation" (73%), "before preparing food" (53%) and "when they are dirty" (43%) were the three most common self-reported behaviours. Routine was the most common motivation to clean, but this was age dependent. There was low correlation between visual detection of dirt/soil and bacterial enumeration. Visual detection of soils was dependent on type and concentration of food soils and material of the surface; the soils were more easily detected on laminate surfaces than plastic and wood. Campylobacter died rapidly, while Salmonella survived for at least one week in food soils drying on a countertop laminate surface. Presence of food soils in concentrations that can be detected visually, protected Salmonella against drying. In conclusion, selecting materials where soil/dirt can easily be detected visually in the kitchen surfaces, may motivate consumers to clean and will reduce risk, but establishing a habit to clean surfaces soon after food preparation is also important from a food safety perspective.
Food microbiology, 2018
The application of lytic phages as biocontrol agents is emerging as a promising strategy towards ... more The application of lytic phages as biocontrol agents is emerging as a promising strategy towards elimination or reduction of foodborne pathogens in a variety of food products. This technology is particularly advantageous for minimally processed and ready-to-eat (RTE) foods. In this study, the potential use of Listex™ P100 combined with high hydrostatic pressure (HPP), to enhance the control of Listeria monocytogenes in food was evaluated. For that, the effect of three pressures (200, 300 or 400 MPa; 5 min, 10 °C) on phage P100 stability was tested when inoculated in six different matrices: phosphate buffered saline (PBS, pH 7.4); apple juice (pH 3.41); orange/carrot nectar (pH 3.54); UHT whole milk (pH 6.73); and, two traditional Portuguese fermented products, "Serra da Estrela" cheese (pH 5.66) and "Alheira", a meat sausage (pH 6.07). The results showed that treatment at 400 MPa reduced phage titres to below the detection level in all matrices, whereas at milder...
Eurosurveillance, 2015
In Portugal, listeriosis has been notifiable since April 2014, but there is no active surveillanc... more In Portugal, listeriosis has been notifiable since April 2014, but there is no active surveillance programme for the disease. A retrospective study involving 25 national hospitals led to the detection of an outbreak that occurred between March 2009 and February 2012. The amount of time between the start of the outbreak and its detection was 16 months. Of the 30 cases of listeriosis reported, 27 were in the Lisbon and Vale do Tejo region. Two cases were maternal/neonatal infections and one resulted in fetal loss. The mean age of the non-maternal/neonatal cases was 59 years (standard deviation: 17); 13 cases were more than 65 years-old. The case fatality rate was 36.7%. All cases were caused by molecular serogroup IVb isolates indistinguishable by pulsed-field gel electrophoresis and ribotype profiles. Collaborative investigations with the national health and food safety authorities identified cheese as the probable source of infection, traced to a processing plant. The magnitude of t...
Microorganisms in Industry and Environment - From Scientific and Industrial Research to Consumer Products - Proceedings of the III International Conference on Environmental, Industrial and Applied Microbiology (BioMicroWorld2009), 2010
Healthy adults and children occasionally get infected with Listeria, but they rarely become serio... more Healthy adults and children occasionally get infected with Listeria, but they rarely become seriously ill.
Objective. A total of 725 Listeria monocytogenes isolates, 607 from various foods and 118 from cl... more Objective. A total of 725 Listeria monocytogenes isolates, 607 from various foods and 118 from clinical cases of listeriosis, were investigated concerning their ability to form biofilms, at 4 ∘ C during 5 days and at 37 ∘ C during 24 h. Methods. Biofilm production was carried out on polystyrene tissue culture plates. Five L. monocytogenes isolates were tested for biofilm formation after being exposed to acidic and osmotic stress conditions. Results. Significant differences (< 0.01) between clinical and food isolates were observed. At 37 ∘ C for 24 h, most food isolates were classified as weak or moderate biofilm formers whereas all the clinical isolates were biofilm producers, although the majority were weak. At 4 ∘ C during 5 days, 65 and 59% isolates, from food and clinical cases, respectively, were classified as weak. After both sublethal stresses, at 37 ∘ C just one of the five isolates tested was shown to be more sensitive to subsequent acidic exposure. However, at 4 ∘ C both stresses did not confer either sensitivity or resistance. Conclusions. Significant differences between isolates origin, temperature, and sublethal acidic stress were observed concerning the ability to form biofilms. Strain, origin, and environmental conditions can determine the level of biofilm production by L. monocytogenes isolates.
Journal of Food Protection, 2014
Over the last 10 to 15 years, increasing evidence suggests that persistence of Listeria monocytog... more Over the last 10 to 15 years, increasing evidence suggests that persistence of Listeria monocytogenes in food processing plants for years or even decades is an important factor in the transmission of this foodborne pathogen and the root cause of a number of human listeriosis outbreaks. L. monocytogenes persistence in other food-associated environments (e.g., farms and retail establishments) may also contribute to food contamination and transmission of the pathogen to humans. Although L. monocytogenes persistence is typically identified through isolation of a specific molecular subtype from samples collected in a given environment over time, formal (statistical) criteria for identification of persistence are undefined. Environmental factors (e.g., facilities and equipment that are difficult to clean) have been identified as key contributors to persistence; however, the mechanisms are less well understood. Although some researchers have reported that persistent strains possess specifi...
Foodborne Pathogens and Disease, 2013
The aim of this study was to characterize a broad collection of isolates of Listeria monocytogene... more The aim of this study was to characterize a broad collection of isolates of Listeria monocytogenes, of different serotypes, recovered in Portugal between 2003 and 2007 from foods (n=353) and from clinical cases of human listeriosis (n=95), in terms of antimicrobial susceptibility. All the isolates were susceptible to ampicillin, the preferred agent to treat listeriosis. Resistances to nitrofurantoin (n=99), to ciprofloxacin (n=18), to erythromycin (n=10), to tetracycline (n=2), to gentamicin (n=1) and to rifampicin (n=1) were observed. One hundred (28.3%) and 20 (21.0%) food and clinical isolates, respectively, were resistant to at least one antibiotic. Eight isolates (1.8%) were resistant to two or more antimicrobials of different classes, and all were collected from foods. Serogroup IVb included the highest percentage of isolates resistant to erythromycin. The highest percentages of isolates resistant to nitrofurantoin were of serogroup IVb and IIc. It was demonstrated that the incidence of antibiotic-resistant isolates of L. monocytogenes, during the period 2003 to 2007, was low in Portugal but still higher than that observed in other countries. Given the increasing population at greater risk of listeriosis, namely, the elderly, the high mortality rate of the infection and the detection of resistant isolates, monitoring for antibiotic resistance in strains of L. monocytogenes on a large scale, and assessing the risk of infection by these strains, is highly recommended.