The occurrence of disease outbreaks involving low‐water‐activity (aw) foods has gained increased prominence due in part to the fact that reducing free water in these foods is normally a measure that controls the growth and multiplication of pathogenic microorganisms. Salmonella, one of the main bacteria involved in these outbreaks, represents a major public health problem worldwide and in Brazil, which highlights the importance of good manufacturing and handling practices for food quality. The virulence of this pathogen, associated with its high ability to persist in the environment, makes Salmonella one of the main challenges for the food industry. The objectives of this article are to present the general characteristics, virulence, thermoresistance, control, and relevance of Salmonella in foodborne diseases, and describe the so‐called low‐water‐activity foods and the salmonellosis outbreaks involving them.

Strains of Salmonella spp. with resistance to antimicrobial drugs are now widespread in both developed and developing countries. In developed countries it is now increasingly accepted that for the most part such strains are zoonotic in origin and acquire their resistance in the food-animal host before onward transmission to humans through the food chain. Of particular importance since the early 1990s has been a multiresistant strain of Salmonella typhimurium definitive phage type (DT) 104, displaying resistance to up to six commonly used antimicrobials, with about 15% of isolates also exhibiting decreased susceptibility to ciprofloxacin. Mutations in the gyrA gene in such isolates have been characterised by a PCR LightCycler-based gyrA mutation assay, and at least four different mutations have been identified. Multiple resistance (to four or more antimicrobials) is also common in the poultry-associated pathogens Salmonella virchow and Salmonella hadar, with an increasing number of strains of these serotypes exhibiting decreased susceptibility to ciprofloxacin. Multiple resistance is also being found in other serotypes in several other European countries, and has been associated with treatment failures. For Salmonella typhi, multiple drug resistance is now the norm in strains originating in the Indian subcontinent and south-east Asia. Such multiresistant strains have been responsible for several epidemics and some of these have been associated with contaminated water supplies. Furthermore, an increasing number of multiresistant strains of S. typhi are now exhibiting decreased susceptibility to ciprofloxacin, with concomitant treatment failures. In developed countries antimicrobial resistance in zoonotic salmonellas has been attributed to the injudicious use of antimicrobials in food-producing animals. It is hoped that the application of Codes of Practice for the use of such agents, which have been prepared by the pharmaceutical industry in response to widespread international concern about the development of drug resistance in bacterial pathogens, will now result in a widespread reduction in the incidence of drug-resistant salmonellas in food production animals and humans on an international scale.

El propósito de esta investigación fue determinar el perfil microbiológico de alimentos de baja actividad de agua (Aw) y a su vez conocer el comportamiento de Salmonella en estos productos. Frutos secos (nueces y cacahuetes), frutas deshidratadas (pasas y jitomates secados al sol) y muestras de chocolate. Se recolectaron 350 muestras de productos vendidos a granel en mercados de la ciudad de Querétaro. Se cuantificó el contenido de bacterias mesófilas aerobias (BMA), coliformes totales (CT), Escherichia coli, hongos y levaduras, así como la detección por métodos convencionales, de Salmonella enterica y Staphylococcus aureus. Adicionalmente, se realizó la estandarización de una técnica de detección molecular para norovirus en muestras de cacahuates, nueces, pasas y jitomate secado al sol. Los valores de las medianas de los microorganismos indicadores en los cinco productos oscilaron entre 3.1 a 5.2 Log UFC/g para BMA, 0.6-1.2 Log NMP/g para CT, 0.5-0.9 Log NMP/g para E. coli, 1.7-2.4 Log UFC/g para los hongos, 2.0-2.8 Log UFC/g para levaduras levaduras. En ninguna muestra se detectó S. aureus. Por el contrario la presencia de Salmonella de detectó en cacahuates (31 %), nueces (40 %), pasas (30 %), tomate secado al sol (56 %) y chocolate (26 %). El método que resultó efectivo para la detección de Norovirus Murino (MNV-1) consistió en extracción de RNA seguida por RT-PCR; se lograron detectar concentraciones de 2.6, ~0.6, <1 y <1 Log PFU/g en cacahuates, nueces, tomates secados al sol y pasas. | The purpose of this investigation was to determine the microbiological profile of low water activity food items and to know the surveillance of Salmonella in these products. Nuts (pecans and peanuts), dehydrated fruits (raisins and sun-dried tomatoes) and chocolate samples (a total of 350) sold in bulk were collected in city markets. Aerobic Plate Count (APC), Coliforms (TC), E. coli, molds and yeasts quantifications and Salmonella spp. and Staphylococcus aureus detection were carried out by conventional methods. In addition the standardization of a molecular detection technique for norovirus from peanuts, pecans, raisins and sun dried tomato samples was carried out. For the determination of indicator microorganisms the medians observed for the five products are between the values 3.1-5.2 Log CFU/g for APC, 0.6-1.2 Log MPN/g for TC, 0.5-0.9 Log MPN/g for E. coli, 1.7-2.4 Log CFU/g for molds, 2.0-2.8 Log CFU/g for yeasts; there was no detection of positive thermonuclease S. aureus in any sample. Salmonella spp was detected in all the analyzed products: peanuts 31 %, pecans 40 %, raisins 30 %, sun-dried tomato 56 %, and chocolate 26 %. RNA extraction followed by RT-PCR was able to detect the minimum MNV-1 concentrations: peanuts and pecans up to 2.6 Log PFU/g and up to ~0.6 Log PFU/g, respectively. Sun-dried tomatoes showed detection to <1 Log PFU/g and raisins to <1 Log PFU/g.

Salmonella can survive for extended periods of time in low-moisture environments posing a challenge for modern food production. This dangerous pathogen must be controlled throughout the production chain with a minimal risk of dissemination. Limited information is currently available describing the behavior and characteristics of this important zoonotic foodborne bacterium in low-moisture food production environments and in food. In our study, the phenotypes related to low-moisture survival of 46 Salmonella isolates were examined. Most of the isolates in the collection could form biofilms under defined laboratory conditions, with 57% being positive for curli fimbriae production and 75% of the collection positive for cellulose production, which are both linked with stronger biofilm formation. Biocides in the factory environment to manage hygiene were found to be most effective against planktonic cells but less so when the same bacteria were surface dried or present as a biofilm. Cellulose-producing isolates were better survivors when exposed to a biocide compared with cellulose-negative isolates. Examination of Salmonella growth of these 18 serotypes in NaCl, KCl, and glycerol found that glycerol was the least inhibitory of these three humectants. We identified a significant correlation between the ability to survive in glycerol and the ability to survive in KCl and biofilm formation, which may be important for food safety and the protection of public health.

Lateral flow immunoassays (LFIAs) are advantageous over conventional detection methods in terms of their simplicity and rapidity. These assays have been reported using various types of labels but colloidal gold nanoparticles are still the preferred choice as a label because of their easy synthesis, visual detection and stability. Bacterial contamination of food and drinking water is a major threat and hindrance towards ensuring food and water safety. Enterobacteriaceae family members are mainly transmitted by the consumption of contaminated water and food and implicated in various food or water borne infections. The LFIAs have been popularly used for detection of bacterial cells in different matrices. Therefore, this review intends to provide an analysis of the gold nanoparticle based lateral flow assays developed for detecting enterobacteriaceae family members in food and water samples. The review includes detailed data and discusses the factors that influence the performance of LFIAs and their shortcomings.

In Japan, strategies for ensuring food safety have been developed without reliable scientific evidence on the relationship between foodborne diseases and food sources. This study aimed to provide information on the proportions of foodborne diseases caused by seven major causative pathogens (Campylobacter spp., Salmonella, enterohemorrhagic Escherichia coli [EHEC], Vibrio parahaemolyticus, Clostridium perfringens, Staphylococcus aureus, and norovirus) attributed to foods and to explore factors affecting changes in these source attribution proportions over time using analysis of outbreak surveillance data. For the calculation of the number of outbreaks attributed to each source, simple-food outbreaks were assigned to the single-food category in question, and complex-food outbreaks were classified under each category proportional to the estimated probability. During 2007 to 2018, 8,730 outbreaks of foodborne diseases caused by seven pathogens were reported, of which 6,690 (76.6%) were of unknown source. We estimated the following source attribution proportions of foodborne diseases: chicken products (80.3%, 95% uncertainty interval [UI] 80.1 to 80.4) for Campylobacter spp.; beef products (50.1%, UI 47.0 to 51.5) and vegetables (42.3%, UI 40.9 to 45.5) for EHEC; eggs (34.6%, UI 27.8 to 41.4) and vegetables (34.4%, UI 27.8 to 40.8) for Salmonella; finfish (50.3%, UI 33.3 to 66.7) and shellfish (49.7%, UI 33.3 to 66.7) for V. parahaemolyticus; grains and beans (57.8%, UI 49.7 to 64.9) for S. aureus; vegetables (63.6%, UI 48.5 to 74.6), chicken products (12.7%, UI 4.6 to 21.5), and beef products (11.1%, UI 8.5 to 13.1) for C. perfringens; and shellfish (75.5%, UI 74.7 to 76.2) for norovirus. In this study, we provide the best available evidence-based information to evaluate the link between foodborne diseases and foods. Our results on source attribution for Campylobacter spp. and EHEC suggest that the strict health regulations for raw beef were reflected in the proportions of these diseases attributed to this food.

Alkaline electrolyzed water (REW) is known for its cleaning action. The aim of this work was to assess REW effectiveness in reducing microbial load on surfaces intended for contact with food. Stainlesssteel surfaces were experimentally contaminated, bacterial inactivation was tested before and after treatment with REW. Treatment with REW was operated spraying it on the contaminated plates until drying. Tests were conducted for Salmonella spp., Listeria spp., Staphylococcus aureus and Escherichia coli. The treatment revealed different degrees of sanitizing activity of REW on different bacterial species, with higher efficacy on E. coli and Salmonella spp. than S. aureus, Listeria spp.. Statistical analysis revealed a significant microbial load reduction (p<0.01) after treatment with REW, suggesting that it has a good disinfectant activity which, along with its easy and safe use, makes it a good alternative to many other more widely used disinfectants.

El agua electrolizada neutra (AEN) ha mostrado gran capacidad para la inactivación de microorganismos relevantes en alimentos. En este proyecto se evaluó la eficiencia del AEN para inactivar Salmonella y alargar la vida útil del queso Oaxaca y la jícama cortada; así como su efecto sobre los principales componentes de los alimentos con la posible formación de compuestos tóxicos. Con la exposición a AEN (56 ppm), Salmonella inoculada en la superficie del queso Oaxaca y trozos de jícama se redujo 0.85 y 1.25 Log UFC/porción, respectivamente. En las bacterias lácticas (BAL) naturalmente presentes en jícama se logró una inactivación de ~ 0.8 Log UFC/porción empleando AEN a 35 y 56 ppm; mientras que en queso Oaxaca se obtuvo una reducción máxima de 0.3 Log UFC/ml cuando se aplicó AEN a 35 ppm. Alargar el tiempo de exposición de 5 a 10 minutos, no mejoró el efecto antimicrobiano sobre Salmonella, ni sobre las BAL. El efecto antimicrobiano del AEN fue similar en todos los casos a una solución de hipoclorito en concentración equivalente, pero el AEN muestra mayor capacidad para conservar su actividad en presencia de materia orgánica. En jícama expuesta a AEN por 5 y 10 minutos no se detectó la formación de hidroperóxidos, mientras que en queso sumergido por 10 min se generaron estos compuestos en 0.4 ppm; en todos los casos la concentración de hidroperóxidos fue menor que en el alimento expuesto a cloro. Cambios en el perfil electroforético de las proteínas solubles del queso sólo se observaron cuando el queso se expuso a AEN por 10 min. La aplicación de AEN (6 y 35 ppm) no marcó una diferencia en las características de color del queso, ni en el comportamiento de las BAL durante el almacenamiento tanto a 30, como a 4°C; sin embargo, se observó un efecto de inhibición de la producción de hidroperóxidos en ambas temperaturas. La aplicación de AEN (6 y 35 ppm) sobre jícama cortada retrasó el deterioro aproximadamente 4 días en el almacenamiento a 4°C, sin cambios en la textura del alimento. La aplicación de AEN a queso y jícama muestra potencial para ser usada como una estrategia complementaria a las prácticas sanitarias en el control de la inocuidad y la vida útil de estos alimentos. | Neutral electrolyzed water (NEW) has shown good capacity for the inactivation of relevant microorganisms in food. In this project, the efficiency of NEW to inactivate Salmonella and to extend shelflife of Oaxaca cheese and cut jicama was evaluated; as well as its effect on toxic productos formation due to interaction with main compounds. With NEW exposition (56ppm), Salmonella on the surface of the Oaxaca cheese and jicama pieces was reduced 0.84 and 1.25 Log CFU/portion, respectively. A reduction of ~ 0.8 Log CFU/portion in lactic acid bacteria (LAB) naturally present in jicama was achieved employing NEW at 35 and 56 ppm; while only a maximum reduction of 0.3 Log CFU/ml was obtained when NEW at 35 ppm was applied. Extending exposure time from 5 to 10 min did not improve the antimicrobial effect. The antimicrobial effect of NEW was similar to a solution of a chloride solution at equivalent concentration in all cases, but NEW showed better capacity to preserve its activity in the presence of organic matter. Hydroperoxides formation was not detected in jicama exposed to NEW for 5 and 10 minutes, while these compounds were generated at 0.4 ppm in cheese immersed for 10 minutes; but in all cases, it was less than hidroperoxide concentration in food exposed to chloride solution. Changes in the electrophoretic profile of soluble proteins of cheese were only observed when the food was exposed to NEW for 10 minutes. NEW application (6 and 35 ppm) did not make a difference in the color characteristics of the cheese, nor in the behavior of the BAL during storage both at 30 and 4 ºC; nevertheless, an inhibition effect was observed in the production of hydroperoxides in both temperatures. The application of NEW (6 and 35 ppm) on cut jicama slowed the spoilage for approximately 4 days at 4ºC storage, without changes in food texture The application of NEW on cheese and jicama shows potential to be used as a complementary strategy to sanitarian practices within food safety control system and its shelflife.

A polymerase chain reaction (PCR) assay with two nested pairs of primers selected from conserved sequences within a 2.3 kb randomly cloned DNA fragment from the Salmonella typhimurium chromosome was developed. The nested PCR assay correctly identified 128 of a total of 129 Salmonella strains belonging to subspecies I, II, IIIb and IV. One strain of Salm. arizona (ssp. IIIa) tested negative. No PCR products were obtained from any of the 31 non-Salmonella strains examined. The sensitivity of the assay was 2 cfu, as determined by analysis of proteinase K-treated boiled lysates of Salm. typhimurium. The performance of the assay was evaluated for environmental water, sewage and food samples spiked with Salm. typhimurium. Water and sewage samples were filtered and filters were enriched overnight in a non-selective medium. Prior to PCR, the broth cultures were subjected to a rapid and simple preparation procedure consisting of centrifugation, proteinase K treatment and boiling. This assay enabled detection of 10 cfu 100 ml(-1) water with background levels of up to 8700 heterotrophic organisms ml(-1) and 10000 cfu of coliform organisms 100 ml(-1) water. Spiked food samples were analysed with and without overnight enrichment in a non-selective medium using the same assay as above. Nested PCR performed on enriched broths enabled detection of < 10 cfu g(-1) food. Variable results were obtained for food samples examined without prior enrichment and most results were negative. This rapid and simple assay provides a sensitive and specific means of screening drinking water or environmental water samples, as well as food samples, for the presence of Salmonella spp.