Cause Of Foodborne Illness Research Articles

Norovirus Transfer between Foods and Food Contact Materials

Human infective noroviruses (NoVs) are a worldwide leading cause of foodborne illness and are frequently spread via infected food handlers preparing and manipulating food products such as deli sandwiches. The objective of the current study was to determine the efficiencies whereby NoV could be transferred between surfaces associated with the preparation of manually prepared foods such as deli sandwiches. Nonfood surfaces included gloves and stainless steel discs, and boiled ham, lettuce, and a sandwich bun were the ingredients of the deli sandwich. Both NoV GII.4 and the murine NoV 1 (MNV-1, a cultivable human NoV surrogate) were included in the presented study. Transfer of NoV GII.4 and MNV-1 between surfaces was performed by pressing an inoculated donor surface against an acceptor surface. To evaluate the effect of subsequent contact, donor surfaces were pressed a second time to an identical acceptor surface. Subsequently, NoV GII.4 and MNV-1 were detected using real-time reverse transcription PCR assays and plaque assays, respectively. Transfer of both viruses from gloves to stainless steel was inefficient, and virus transfer from food products to stainless steel occurred with more variability for NoV GII.4 than for MNV-1. Virus transfer from the stainless steel discs to the gloves was substantially more efficient than from the gloves to the stainless steel. NoV GII.4 and MNV-1 transfer from food products to the gloves occurred with varying efficiencies, although this variation was more evident for NoV GII.4. The MNV-1 inoculum was significantly less efficiently transferred to the acceptor surface at the second contact, which was not the case for NoV GII.4. The obtained transfer efficiency data may provide insights into the transfer of NoV during preparation of foods and can be included in risk assessment models describing the transmission of NoVs in this context.

Virus Inactivation on Hard Surfaces or in Suspension by Chemical Disinfectants: Systematic Review and Meta-Analysis of Norovirus Surrogates

Norovirus (NoV) infections are the leading cause of foodborne illness in the United States. Effective disinfection is important for controlling outbreaks caused by this highly infectious virus but can be difficult to achieve because NoV is very resistant to many common disinfection protocols. The inability of human NoV to replicate in tissue culture complicates NoV research, generally necessitating genome copy quantification, the use of surrogate viruses, or the use of other substitutes such as virus-like particles. To date, comprehensive comparisons among NoV surrogates and between surrogates and human NoV are missing, and it is not clear how best to extrapolate information from surrogate data. We conducted a systematic review and meta-analysis of comparisons of NoV surrogates with regard to their susceptibility to disinfection on hard surfaces or in suspension. Restricting our analysis to those studies in which two or more virus surrogates were compared allowed us to improve the signal-to-noise ratio in our analysis, similar to the epidemiological concept of matching. Using meta-analysis methods, our results indicate that hepatitis A virus, murine norovirus 1, and phage MS2 are significantly more resistant to disinfection than is feline calicivirus, but average differences in viral titer reduction appeared to be modest, 1.5 log PFU or less in all cases. None of the studies that compared surrogates and human NoV met our inclusion criteria, precluding a direct comparison between human NoV and NoV surrogates in this study. For all surrogates with sufficient data available to permit subgroup analyses, we detected strong evidence that the type of disinfectant impacted the relative susceptibility of the surrogates. Therefore, extrapolation of results between surrogates or from surrogates to human NoV must consider the type of disinfectant studied.

Prevalence of Hepatitis A Virus in Bivalve Molluscs Sold in Granada (Spain) Fish Markets

Viruses are the leading cause of foodborne illness associated with the consumption of raw or slightly cooked contaminated shellfish. The aim of this study was to evaluate the prevalence of hepatitis A virus in molluscs. Standard and real-time reverse transcription-polymerase chain reaction procedures were used to monitor bivalve molluscs from the Granada fish markets (southern Spain) for this human enteric virus. Between February 2009 and October 2010, we collected a total of 329 samples of different types of bivalve molluscs (mussels, smooth clams, striped venus, and grooved clams). The results showed the presence of hepatitis A virus in 8.5% of the 329 samples analyzed. We can therefore confirm that conventional fecal indicators are unreliable for demonstrating the presence or absence of viruses. The presence of hepatitis A virus in molluscs destined for human consumption is a potential health risk in southern Spain.

Salmonella enterica Biofilm Formation and Density in the Centers for Disease Control and Prevention's Biofilm Reactor Model Is Related to Serovar and Substratum

Foodborne pathogens can attach to, and survive on, food contact surfaces for long periods by forming a biofilm. Salmonella enterica is the second most common cause of foodborne illness in Ireland. The ability of S. enterica to form a biofilm could contribute to its persistence in food production areas, leading to cross-contamination of products and surfaces. Arising from a large foodborne outbreak of S. enterica serovar Agona associated with a food manufacturing environment, a hypothesis was formulated that the associated Salmonella Agona strain had an enhanced ability to form a biofilm relative to other S. enterica. To investigate this hypothesis, 12 strains of S. enterica, encompassing three S. enterica serovars, were assessed for the ability to form a biofilm on multiple food contact surfaces. All isolates formed a biofilm on the contact surfaces, and there was no consistent trend for the Salmonella Agona outbreak strain to produce a denser biofilm compared with other strains of Salmonella Agona or Salmonella Typhimurium. However, Salmonella Enteritidis biofilm was considerably less dense than Salmonella Typhimurium and Salmonella Agona biofilms. Biofilm density was greater on tile than on concrete, polycarbonate, stainless steel, or glass.

Pathogen-specific risk of chronic gastrointestinal disorders following bacterial causes of foodborne illness

BackgroundThe US CDC estimates over 2 million foodborne illnesses are annually caused by 4 major enteropathogens: non-typhoid Salmonella spp., Campylobacter spp., Shigella spp. and Yersinia enterocoltica. While data suggest a number of costly and morbid chronic sequelae associated with these infections, pathogen-specific risk estimates are lacking. We utilized a US Department of Defense medical encounter database to evaluate the risk of several gastrointestinal disorders following select foodborne infections.MethodsWe identified subjects with acute gastroenteritis between 1998 to 2009 attributed to Salmonella (nontyphoidal) spp., Shigella spp., Campylobacter spp. or Yersinia enterocolitica and matched each with up to 4 unexposed subjects. Medical history was analyzed for the duration of military service time (or a minimum of 1 year) to assess for incident chronic gastrointestinal disorders. Relative risks were calculated using modified Poisson regression while controlling for the effect of covariates.ResultsA total of 1,753 pathogen-specific gastroenteritis cases (Campylobacter: 738, Salmonella: 624, Shigella: 376, Yersinia: 17) were identified and followed for a median of 3.8 years. The incidence (per 100,000 person-years) of PI sequelae among exposed was as follows: irritable bowel syndrome (IBS), 3.0; dyspepsia, 1.8; constipation, 3.9; gastroesophageal reflux disease (GERD), 9.7. In multivariate analyses, we found pathogen-specific increased risk of IBS, dyspepsia, constipation and GERD.ConclusionsThese data confirm previous studies demonstrating risk of chronic gastrointestinal sequelae following bacterial enteric infections and highlight additional preventable burden of disease which may inform better food security policies and practices, and prompt further research into pathogenic mechanisms.

Uptake and Retention of Vibrio parahaemolyticus in a Cohabitating Population of Ruditapes decussatus and Ruditapes philippinarum Under Experimental Conditions

The presence of Vibrio parahaemolyticus in bivalve mollusc is an important cause of foodborne illnesses, and their levels are influenced by environmental changes, such as temperature and salinity. Clams are common species in estuaries and are used in environmental monitoring programmes. Present study compared the uptake and retention of nonpathogenic V. parahaemolyticus by two species of clam (Ruditapes decussatus and R. philippinarum), cohabitating in a closed system. Results showed no significant differences were found between both species of clams. Bacterial levels are following a similar trend with values between 3.48 and 3.70logCFU/g for R. decussatus and between 3.15 and 3.49logCFU/g for R. philippinarum. So, in the absence of water renewal, high and stable levels of V. parahaemolyticus were observed in cultured clams after exposure. Changes in physical parameters should be taken into account to design surveillance programmes in bivalves, and sampling should focus on species that have faster filtration rates at that water temperature since they potentially represent the worst-case scenario.

Prevalence of Salmonella in Apparently Healthy Chickens in Mymensingh, Bangladesh

Salmonella spp. are the most frequently reported cause of food-borne illnesses worldwide that are closely associated with the consumption of contaminated poultry and egg products. This study was designed to isolate and identify Salmonella, and evaluate its prevalence in chickens of different lines and ages during summer and rainy seasons. Cloacal swab samples (n=200) of apparently healthy chickens were collected. Isolated Salmonella were characterized using cultural, biochemical and serological examinations. A total of 104 samples (52%) were found to be positive for Salmonella spp. The prevalence of Salmonella spp. was significantly higher (p<0.01) during summer (67.78%) as opposed to rainy season (39.09%). Prevalence of Salmonella was 71.11% in broiler, 38.89% in layer and 25% in indigenous chicken. Broilers showed significantly higher prevalence of Salmonella as compared to layer and indigenous chickens (p<0.01). Among the five age groups, the highest prevalence was observed in chickens of 18-week of age (65%) and the lowest was in chickens of 2-week age (16.67%). The data of this study showed higher prevalence of Salmonella in broilers and underscored the need for detail epidemiological investigations as well as strict hygienic practices in farm and live bird markets all over Bangladesh. DOI: http://dx.doi.org/10.3329/mh.v1i1.13711 Microbes and Health Vol.1(1) June 2012 pp.30-33

Unusual Occurrence of Staphylococcus warneri as Endophyte in Fresh Fruits along with Usual Bacillus spp

AbstractIn the present study, we obtained several bacterial isolates from direct plating (without enrichment) of the diluted extract of apples and oranges obtained from commercial market of major cities in Tamil Nadu, India. Based on the cultural growth characteristics in different selective media, the isolates were grouped into four groups. The 16S rRNA gene was amplified using universal primers. The expected amplified fragments were obtained in four isolates belonging to two culture groups and were sequenced. This resulted in the identification of Staphylococcus warneri and Bacillus pumilis in apples and B. flexus and B. subtilis in oranges. The different species of Bacillus are reported already as endophytes in plants and plant‐derived produce. However, the occurrence of S. warneri is unusual. The observation emphasizes the need to further our understanding of the changing ecology of bacteria, particularly human pathogenic Staphylococcus, which has adapted to inner tissues of fruits.Practical ApplicationIdentification and detection of human pathogenic bacteria like Staphylococcus in fresh fruits is applicable in creating awareness among the public about the route cause of foodborne illness because of consumption of unhealthful raw and unpasteurized juices. In addition, this study helps us to reevaluate the present production and handling practices of fruits. It also emphasizes the need for developing strategies based on a coordinated approach by the growers, distributors, retailers, importers and public health officials to eliminate or contain such human pathogenic bacteria in fresh fruits.

Epidemiology of foodborne disease outbreaks caused by Clostridium perfringens, United States, 1998-2010.

Clostridium perfringens is estimated to be the second most common bacterial cause of foodborne illness in the United States, causing one million illnesses each year. Local, state, and territorial health departments voluntarily report C. perfringens outbreaks to the U.S. Centers for Disease Control and Prevention through the Foodborne Disease Outbreak Surveillance System. Our analysis included outbreaks confirmed by laboratory evidence during 1998-2010. A food item was implicated if C. perfringens was isolated from food or based on epidemiologic evidence. Implicated foods were classified into one of 17 standard food commodities when possible. From 1998 to 2010, 289 confirmed outbreaks of C. perfringens illness were reported with 15,208 illnesses, 83 hospitalizations, and eight deaths. The number of outbreaks reported each year ranged from 16 to 31 with no apparent trend over time. The annual number of outbreak-associated illnesses ranged from 359 to 2,173, and the median outbreak size was 24 illnesses. Outbreaks occurred year round, with the largest number in November and December. Restaurants (43%) were the most common setting of food preparation. Other settings included catering facility (19%), private home (16%), prison or jail (11%), and other (10%). Among the 144 (50%) outbreaks attributed to a single food commodity, beef was the most common commodity (66 outbreaks, 46%), followed by poultry (43 outbreaks, 30%), and pork (23 outbreaks, 16%). Meat and poultry outbreaks accounted for 92% of outbreaks with an identified single food commodity. Outbreaks caused by C. perfringens occur regularly, are often large, and can cause substantial morbidity yet are preventable if contamination of raw meat and poultry products is prevented at the farm or slaughterhouse or, after contamination, if these products are properly handled and prepared, particularly in restaurants and catering facilities.

Using Risk Factor Weighting to Target and Create Effective Public Health Policy for Campylobacteriosis Prevention in Ontario, Canada

Campylobacter is one of the major causes of foodborne illness globally, making prevention of Campylobacter infections a significant public health concern. Factors such as under-reporting and the low dose required to cause illness make surveillance and control of food-acquired campylobacteriosis challenging. A literature review was conducted to identify articles that included relevant information about the causes of foodborne illness, transmission of Campylobacter, specific risk factors associated with food-acquired Campylobacter infection and reported numbers of cases of Campylobacter. The majority of studies determine that specific demographic groups are at a higher risk for contracting foodborne illness, with age, gender and location being the most significant factors. Food-acquired campylobacteriosis accounts for up 74 to 85% of total cases, with poultry being the number one contributing vehicle. Location of food-acquired Campylobacter infection differs between countries. In Ontario, the majority of food-acquired campylobacteriosis cases are attributed to food prepared in the home. A risk factor diagram shows the source of Campylobacter organisms and the locations where people are exposed. It then shows causes of food-acquired Campylobacter infection, dividing them into human and non-human factors. Human factors are the major contributing causes of Campylobacter infection in people. Targeted policies should be developed which target these factors and address the specific groups that are at a higher risk for foodborne illness. Policy initiatives that focus on consumer level human factors will have the greatest impact on campylobacteriosis prevention. Further research needs to be conducted to determine the proportion of foodborne illness which can be attributed to specific risk factors and why consumers and food handlers do not follow proper procedures for minimizing exposure to Campylobacter organism. Targeted policies can provide a more cost-effective way to help prevent further cases of Campylobacter infection as well as improve disease surveillance.

Evaluation of whole-genome sequencing as a genotyping tool for Campylobacter jejuni in comparison with pulsed-field gel electrophoresis and flaA typing

Campylobacter jejuni is a leading cause of foodborne illness, with poultry and poultry products being leading sources of infection. Epidemiological efforts to trace Campylobacter can be challenging because of the extreme genetic diversity of this bacterium relative to other foodborne pathogens. To enhance tracking and epidemiological efforts, whole-genome sequencing has been used for other foodborne pathogens but not yet been evaluated for practicality with Campylobacter. Thus, the purpose of this study was to evaluate whole-genome sequencing as a genotyping method for C. jejuni by comparing it with 2 commonly used genotyping methods, namely pulsed-field gel electrophoresis (PFGE) and flaA typing. Whole-genome sequence data were generated using the Roche-454 sequencing platform to map Campylobacter strains (VOL_3, VOL_5, VOL_8, VOL_11, and VOL_20) isolated from conventional and organic poultry. Five additional isolates with published genomes were also compared. The PFGE profiles were created using Sma I digestion. For the flaA short variable region sequencing, standard PCR methods were used and high-quality Sanger reads were generated. The PFGE profiles of strains VOL_3 and VOL_11 were found to be indistinguishable, and strain VOL_20 was found indistinguishable from NCTC 11168. Whole-genome comparisons between strains VOL_20 and 11168 were in agreement with the obtained PFGE profiles, as these 2 isolates had very similar genome sizes, a number of shared genes (1,580), and very similar % G-C content (30.6). Of the 8 strains, 2 strains (VOL_3 and VOL_11) had identical flaA types. Whole-genome sequencing was the most discriminatory of the typing methods. However, the cost and time effort needed to sequence and assemble the genomes may hinder efforts, and therefore, we conclude that more bioinformatics tools need to be developed for whole-genome sequencing to be used as an epidemiological tool.

A Study of Salmonella Carriage among Asymptomatic Food-Handlers in Southern Ethiopia

Background: Salmonella is the most frequently reported cause of food borne illness in Ethiopia. Objective: The aim of this study was to screen food handlers in the Dilla area of Southern Ethiopia and to assess the scale of carriage of Salmonella species and to offer prophylaxis followed by re-testing and advice on personal and food hygiene as appropriate. Method: Stool samples were collected from a total of 107 food handlers from various establishments in the area. Enrichment culture using Selenite broth and sub-culture on to Deoxycholate Citrate agar was used followed by identification to genus level by use of a commercially available biochemical kit and polyvalent antisera. Result: Salmonella was isolated from one food handler only and this person could not be traced having left her employment and not having left a forwarding address. Conclusion: As food poisoning is a main issue in Ethiopia further epidemiological research, to monitor those found to be infected is mandatory.

Electron Microscopic Study of <i>Kudoa septempunctata</i> Infecting <i>Paralichthys olivaceus</i> (Olive Flounder)

Kudoa septempunctata is a myxosporean parasite of Paralichthys olivaceus (olive flounder) that causes more than 50 cases of foodborne illness in Japan each year. For quantitatively assessing the presence of K. septempunctata spores in the causative fish at food poisoning outbreaks, both a direct observation method using microscopy and a quantitative real-time PCR (qRT-PCR) method are officially accepted in Japan. However, lower correlations have been often noticed between the number of spores counted using the direct observation method and the DNA amount determined using the qRT-PCR method. To elucidate the cause of this discrepancy, we observed muscle tissues of infected olive flounders with K. septempunctata by transmission electron microscopy. The images demonstrated unsynchronized development of K. septempunctata spores in plasmodia found within myofibers; in other words, the plasmodium contained not only developed spores with completed shell valves but also developing spores (sporoblasts) composed of spore-forming cells without shell valves. Furthermore, the ratio between developed spores and sporoblasts varied at different parts of muscles. The direct microscopic observation method could count developed spores, whereas the qRT-PCR method could quantify the amount of not only spores but also sporoblastic cells regardless of the cellular development and differentiation. Considering that the food toxicity caused by K. septempunctata is induced by viable spores passing through the gastric environment, the direct observation method counting only developed spores is better than the qRT-PCR method for assessing the cause of foodborne illness at the outbreak as well as the risk of human illness in monitoring surveys of aquacultured or natural-water fish.

Multiplex PCR (mPCR) for the Detection of Salmonella spp. and the Differentiation of the Typhimurium and Enteritidis Serovars in Chicken Meat

AbstractSalmonella enterica subspecies enterica serovars Enteritidis and Typhimurium are important causes of foodborne illness. Methods for simultaneous detection of these serovars may contribute for the adoption of measures to prevent these diseases. The polymerase chain reaction to detect individually or simultaneously the serovars Enteritidis and Typhimurium in foods have been standardized; however, the majority of assays employ the fliC gene as a target for detection of serovar Typhimurium. The detection of these sorovars in a few hours allows the food supply chain to take appropriate measures to prevent the distribution of contaminated food. The aim of this study was to develop a new multiplex PCR (mPCR) for the simultaneous detection and differentiation of Salmonella spp., S. Enteritidis and S. Typhimurium in chicken meat. The mPCR assays showed high specificity and differentiated S. Typhimurium from 22 Salmonella serovars tested, including S. Kentucky, showing that it's an alternative to reduce the time required to obtain presumptive positive results.Practical ApplicationsThe fliC gene used as target for the detection of serovar Typhimurium is questionable as it has also been described for S. Kentucky. The amplification of STM4492 gene in this study, instead of fliC gene, exhibited high specificity to detect S. Typhimurium. The developed mPCR is an efficient means for the simultaneous detection and differentiation of Salmonella spp., S. Enteritidis and S. Typhimurium in chicken meat after 24 h of enrichment. The mPCR has the potential to be used in routine diagnostic laboratories to obtain presumptive positive results and for identification of Enteritidis and Typhimurium strains isolated by the conventional method.

Cattle Drive Salmonella Infection in the Wildlife–Livestock Interface

The genus Salmonella is found throughout the world and is a potential pathogen for most vertebrates. It is also the most common cause of food-borne illness in humans, and wildlife is an emerging source of food-borne disease in humans due to the consumption of game meat. Wild boar is one of the most abundant European game species and these wild swine are known to be carriers of zoonotic and food-borne pathogens such as Salmonella. Isolation of the pathogen, serotyping and molecular biology are necessary for elucidating epidemiological connections in multi-host populations. Although disease management at population level can be addressed using a number of different strategies, such management is difficult in free-living wildlife populations due to the lack of experience with the wildlife-livestock interface. Herein, we provide the results of a 4-year Salmonella survey in sympatric populations of wild boar and cattle in the Ports de Tortosa i Beseit National Game Reserve (NE Spain). We also evaluated the effects of two management strategies, cattle removal and increased wild boar harvesting (i.e. by hunting and trapping), on the prevalence of the Salmonella serovar community. The serovars Meleagridis and Anatum were found to be shared by cattle and wild boar, a finding that was confirmed by 100% DNA similarity patterns using pulse field gel electrophoresis. Cattle removal was more efficient than the culling of wild boar as a means of reducing the prevalence of shared serotypes, which underlines the role of cattle as a reservoir of Salmonella for wild boar. To our knowledge, this is the first attempt to manage Salmonella in the wild, and the results have implications for management.

Hazard Identification and Exposure Assessment for Bacterial Risk Assessment of Informally Marketed Milk in Abidjan, Côte d'Ivoire

Animal-source foods are important causes of food-borne illness, and milk and dairy products can contain pathogenic microorganisms. We conducted a stochastic assessment of the risk of ingesting milk contaminated with specific microbial pathogens (Escherichia coli, Staphylococcus aureus, and Enterococcus spp.) in Abidjan, Côte d'Ivoire. We carried out structured interviews and focus group discussions with farmers (n = 15), vendors (n = 17), and consumers (n = 188) to characterize dairy production systems and milk consumption behavior. Microbiological sampling was conducted at different points between milking and sale. A risk model was developed, and the risk of consuming contaminated raw milk was estimated by Monte Carlo simulation. The investigation into local raw milk consumption patterns showed that the proportion of raw milk consumption was 51.6% in people who consume milk. The probability of ingestion of marketed raw milk that failed to meet standards for this group of bacteria was 29.9% and about 652 consumers per day were estimated to ingest contaminated milk. Microbiological tests from the farm showed that 7.2% of samples taken from milkers' hands, 4.4% of water samples (water used to rinse milk containers or milking utensils (calabash, plastic bottle, filters, buckets), 4.4% of environmental samples (air pollution), 13.2% of samples from milking utensils, and 4.9% of samples from cows' udders were contaminated with one or more of these pathogens. About 624.6 L of marketed raw milk would need to be discarded per day if discarding milk was chosen as the option of risk reduction. The destruction of this milk would result in a potential loss of Euro623.9 per day for all producers. The risk of human illness from consumption of raw milk could be mitigated by raising awareness about heat treatment of milk and good hygiene practices in the dairy chain.

Restaurant food cooling practices.

Improper food cooling practices are a significant cause of foodborne illness, yet little is known about restaurant food cooling practices. This study was conducted to examine food cooling practices in restaurants. Specifically, the study assesses the frequency with which restaurants meet U.S. Food and Drug Administration (FDA) recommendations aimed at reducing pathogen proliferation during food cooling. Members of the Centers for Disease Control and Prevention's Environmental Health Specialists Network collected data on food cooling practices in 420 restaurants. The data collected indicate that many restaurants are not meeting FDA recommendations concerning cooling. Although most restaurant kitchen managers report that they have formal cooling processes (86%) and provide training to food workers on proper cooling (91%), many managers said that they do not have tested and verified cooling processes (39%), do not monitor time or temperature during cooling processes (41%), or do not calibrate thermometers used for monitoring temperatures (15%). Indeed, 86% of managers reported cooling processes that did not incorporate all FDA-recommended components. Additionally, restaurants do not always follow recommendations concerning specific cooling methods, such as refrigerating cooling food at shallow depths, ventilating cooling food, providing open-air space around the tops and sides of cooling food containers, and refraining from stacking cooling food containers on top of each other. Data from this study could be used by food safety programs and the restaurant industry to target training and intervention efforts concerning cooling practices. These efforts should focus on the most frequent poor cooling practices, as identified by this study.

First Detection ofoqxABin Salmonella spp. Isolated from Food

Food-borne salmonellosis is an important public health problem worldwide and the second leading cause of food-borne illnesses in Hong Kong. In this study, the prevalence and antimicrobial resistance of Salmonella in meat products in Hong Kong were determined. Interestingly, a plasmid-mediated quinolone resistance (PMQR) gene combination, oqxAB, which mediates resistance to nalidixic acid, chloramphenicol, and olaquindox, was for the first time detectable on the chromosomes of two Salmonella enterica serovar Derby isolates. Further surveillance of oqxAB in Salmonella will be needed.

Samsung Salmonella Detection Kit

Salmonella, one of the most common causes of foodborne illness, is a significant public health concern worldwide. There is a need in the food industry for methods that are simple, rapid, and sensitive for the detection of foodborne pathogens. In this study, the Samsung Salmonella Detection Kit, a real-time PCR assay for the detection of Salmonella, was evaluated according to the current AOAC guidelines. The validation consisted of lot-to-lot consistency, stability, robustness, and inclusivity/exclusivity studies, as well as a method comparison of 10 different food matrixes. In the validation, the Samsung Salmonella Detection Kit was used in conjunction with the Applied Biosystems StepOnePlus PCR system and the Samsung Food Testing Software for the detection of Salmonella species. The performance of the assays was compared to the U.S. Department of Agriculture/Food Safety and Inspection Service-Microbiology Laboratory Guidebook (USDA/FSIS-MLG) 4.05: Isolation and Identification of Salmonella from Meat, Poultry, Pasteurized Egg, and Catfish and the and U.S. Food and Drug Administration/Bacteriological Analytical Manual (FDA/BAM) Chapter 5 Salmonella reference methods. The validation was conducted using an unpaired study design for detection of Salmonella spp. in raw ground beef, raw pork, raw ground pork, raw chicken wings, raw salmon, alfalfa sprouts, pasteurized orange juice, peanut butter, pasteurized whole milk, and shell eggs. The Samsung Salmonella Detection Kit demonstrated lot-to-lot consistency among three independent lots as well as ruggedness with minor modifications to changes in enrichment incubation time, enrichment incubation temperature, and DNA sample volume for PCR reaction. Stability was observed for 13 months at -20 degrees C and 3 months at 5 degrees C. For the inclusivity/exclusivity study, the Samsung Salmonella Detection Kit correctly identified 147 Salmonella species isolates out of 147 isolates tested from each of three different enrichment broths (a total of 441 isolates detected), and correctly excluded all 31 nontarget strains analyzed. For the method comparison, statistical analysis was conducted according to the Mantel-Haenszel Chi-square formula for unpaired test portions, and there was no significant difference in the number of positive samples detected between the Samsung Salmonella Detection Kit and the USDA/FSIS-MLG and FDA/BAM reference methods for all 10 food matrixes.

Behavior of different Shiga toxin-producing Escherichia coli serotypes in various experimentally contaminated raw-milk cheeses.

Shiga toxin-producing Escherichia coli (STEC) is an important cause of food-borne illness. The public health implication of the presence of STEC in dairy products remains unclear. Knowledge of STEC behavior in cheeses would help to evaluate the human health risk. The aim of our study was to observe the growth and survival of experimentally inoculated STEC strains in raw-milk cheeses manufactured and ripened according to five technological schemes: blue-type cheese, uncooked pressed cheese with long ripening and with short ripening steps, cooked cheese, and lactic cheese. Cheeses were contaminated with different STEC serotypes (O157:H7, O26:H11, O103:H2, and O145:H28) at the milk preparation stage. STEC growth and survival were monitored on selective media during the entire manufacturing process. STEC grew (2 to 3 log(10) CFU · g(-1)) in blue-type cheese and the two uncooked pressed cheeses during the first 24 h of cheese making. Then, STEC levels progressively decreased in cheeses that were ripened for more than 6 months. In cooked cheese and in lactic cheese with a long acidic coagulation step (pH < 4.5), STEC did not grow. Their levels decreased after the cooking step in the cooked cheese and after the coagulation step in the lactic cheese, but STEC was still detectable at the end of ripening and storage. A serotype effect was found: in all cheeses studied, serotype O157:H7 grew less strongly and was less persistent than the others serotypes. This study improves knowledge of the behavior of different STEC serotypes in various raw-milk cheeses.