Browsing by Author "Esteves, Alexandra"
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- Comprehensive typing and genetic analysis of L. monocytogenes isolates: implication for food safety and antibiotic resistance surveillancePublication . Silva, Adriana; Silva, Vanessa; Borges, Vítor; Coelho, Anabela; Batista, Rita; Esteves, Alexandra; Igrejas, Gilberto; Saraiva, Cristina; Gomes, João Paulo; Poeta, PatríciaListeria species are commonly found in various environments and contaminated food, with livestock serving as a significant source of foodborne pathogens. Among these species, Listeria monocytogenes (L. monocytogenes) is particularly noteworthy as it can affect both livestock and humans. Antibiotics are frequently used in food animals for disease treatment and prevention on a large scale. This practice can lead to the selection of antibiotic-resistant bacterial strains, which can then spread to humans through the food chain. Consequently, L. monocytogenes, a ubiquitous foodborne pathogen, has been associated with global outbreaks of foodborne illnesses. To address this concern, the aim of the study was to conduct comprehensive typing and genetic analysis of 13 L. monocytogenes isolates obtained from food and food-processing environments.Among the 13 L. monocytogenes isolates, eight sequence types (ST) were identified: two isolates were identified as belonging to ST9; one as ST155; four as ST3, two as ST121, one as ST8; one as ST87; one as ST1; and one new ST belonging to CC121. Core-genome clustering analysis of L. monocytogenes was made to assess the genetic relatedness among the isolates. The core genome Multilocus Sequence Typing (cgMLST) analysis revealed three genetic clusters of high closely related isolates (≤7 allelic differences (ADs)): cluster 1. Regarding L. monocytogenes typing, ST3 was the most prevalent among the isolates, found in 4 isolates, followed by ST9 and ST121. Some of these isolates, like ST1, ST9 and ST87, were previously associated with human clinical cases. We used Whole Genome Sequencing (WGS) alongside epidemiological data to link strains to human illnesses and potential food sources. Through cgMLST analysis, we identified genetic clusters of closely related isolates, all linked to the same producers. This approach helped us pinpoint common sources of contamination and gain insights into the transmission dynamics of L. monocytogenes in the context of food safety and public health. The escalating antibiotic resistance in Listeria species, particularly in L. monocytogenes, emphasizes the need for heightened surveillance and improved hygiene practices in the food industry to curb the spread of antibiotic resistance and ensure food safety.
- Hygiene Indicators and Salmonellae on Surfaces of Swine Carcasses from Two Slaughterhouses in Northern PortugalPublication . Moura-Alves, Márcio; Carvalho, Marta; Baggio Ribeiro, Deise Helena; Barbosa, Joana; Silveira, Leonor; Pista, Ângela; Pinto, Helena Patrícia; Saraiva, Cristina; Teixeira, Paula; Esteves, AlexandraAbstract: The monitoring of carcass surface contamination along the slaughter line enables verification of slaughter operation hygiene and the use of good manufacturing practices. Pork meat is a common source of human nontyphoidal salmonellosis, one of the most frequently reported foodborne illnesses worldwide. This study was conducted to gather data on microbial loads before and after evisceration on the surfaces of swine carcasses in two slaughterhouses. The presence of Salmonella enterica was evaluated only after evisceration on carcass surfaces and in livers and floor drains (environmental samples) because pigs are common carriers of this pathogen. The contamination of carcass surfaces was evaluated by delimitation of surface area with sterilized templates (100 cm2), and surface samples were collected with gauze swabs. Total aerobic mesophilic bacteria, Enterobacteriaceae, and Escherichia coli were enumerated. Significant differences (P < 0.05) in counts of mesophilic bacteria, Enterobacteriaceae, and E. coli were found on the external carcass surfaces, with higher counts after evisceration. The neck and abdominal areas had higher levels of mesophilic bacteria, Enterobacteriaceae, and E. coli and a high prevalence of Salmonella. Salmonella was detected in only one of the studied slaughterhouses; 19 (7.3%) of 259 analyzed carcass samples were positive for Salmonella, and Salmonella was detected in two livers and two floor drains. A total of 52 Salmonella isolates (44 from carcasses, 5 from livers, and 3 from drains) were recovered. Three Salmonella serovars (Typhimurium 4,5:i- , Wernigerone, and Derby) were identified, and 53.8% of the 52 isolates were multidrug resistant. The results reveal the need for continuous improvement of slaughtering operations and implementation of good manufacturing practices to ensure the safety of pork produced in Portugal.
- Listeria monocytogenes from Food Products and Food Associated Environments: Antimicrobial Resistance, Genetic Clustering and Biofilm InsightsPublication . Silva, Adriana; Silva, Vanessa; Gomes, João Paulo; Coelho, Anabela; Batista, Rita; Saraiva, Cristina; Esteves, Alexandra; Martins, Ângela; Contente, Diogo; Diaz-Formoso, Lara; Cintas, Luis M.; Igrejas, Gilberto; Borges, Vítor; Poeta, PatríciaListeria monocytogenes, a foodborne pathogen, exhibits high adaptability to adverse environmental conditions and is common in the food industry, especially in ready-to-eat foods. L. monocytogenes strains pose food safety challenges due to their ability to form biofilms, increased resistance to disinfectants, and long-term persistence in the environment. The aim of this study was to evaluate the presence and genetic diversity of L. monocytogenes in food and related environmental products collected from 2014 to 2022 and assess antibiotic susceptibility and biofilm formation abilities. L. monocytogenes was identified in 13 out of the 227 (6%) of samples, 7 from food products (meat preparation, cheeses, and raw milk) and 6 from food-processing environments (slaughterhouse-floor and catering establishments). All isolates exhibited high biofilm-forming capacity and antibiotic susceptibility testing showed resistance to several classes of antibiotics, especially trimethoprim-sulfamethoxazole and erythromycin. Genotyping and core-genome clustering identified eight sequence types and a cluster of three very closely related ST3 isolates (all from food), suggesting a common contamination source. Whole-genome sequencing (WGS) analysis revealed resistance genes conferring resistance to fosfomycin (fosX), lincosamides (lin), fluoroquinolones (norB), and tetracycline (tetM). In addition, the qacJ gene was also detected, conferring resistance to disinfecting agents and antiseptics. Virulence gene profiling revealed the presence of 92 associated genes associated with pathogenicity, adherence, and persistence. These findings underscore the presence of L. monocytogenes strains in food products and food-associated environments, demonstrating a high virulence of these strains associated with resistance genes to antibiotics, but also to disinfectants and antiseptics. Moreover, they emphasize the need for continuous surveillance, effective risk assessment, and rigorous control measures to minimize the public health risks associated to severe infections, particularly listeriosis outbreaks. A better understanding of the complex dynamics of pathogens in food products and their associated environments can help improve overall food safety and develop more effective strategies to prevent severe health consequences and economic losses.