Temporal patterns in the occurrence of Salmonella in raw meat and poultry products and their relationship to human illnesses in the United States

The prevalence and level of microbial pathogens on various commodities often exhibit seasonal patterns. As a consequence, the incidence of foodborne illness tends to follow these trends. Of the various product classes, the occurrence of microbial contamination can be high on raw meat and poultry products, with Salmonella potentially occurring in all meat and poultry product classes. Since 1999, the Food Safety and Inspection Service in the United States has collected samples of meat and poultry products and analyzed them for the presence of Salmonella. This study uses a common modeling approach to estimate the seasonal change in the proportion of test-positive samples for seven classes of raw meat and poultry products. The results generally support the hypothesis of a seasonal increase of Salmonella during the summer months. The proportions of test-positive samples decrease rapidly in the late fall for all product classes except chicken and ground turkey, which remain somewhat elevated through late winter. A comparison of the pathogens' seasonal pattern in meat and poultry with human cases reveals that the seasonal increase in human cases precedes the seasonal increase in meat and poultry by between one and three months. These results suggest that while contaminated meat and poultry products may be responsible for a substantial number of human cases, they are not necessarily the primary driver of the seasonal pattern in human salmonellosis.     

Quantifying the size‐resolved dynamics of indoor bioaerosol transport and control

Understanding the bioaerosol dynamics of droplets and droplet nuclei emitted during respiratory activities is important for understanding how infectious diseases are transmitted and potentially controlled. To this end, we conducted experiments to quantify the size‐resolved dynamics of indoor bioaerosol transport and control in an unoccupied apartment unit operating under four different HVAC particle filtration conditions. Two model organisms (Escherichia coli K12 and bacteriophage T4) were aerosolized under alternating low and high flow rates to roughly represent constant breathing and periodic coughing. Size‐resolved aerosol sampling and settle plate swabbing were conducted in multiple locations. Samples were analyzed by DNA extraction and quantitative polymerase chain reaction (qPCR). DNA from both organisms was detected during all test conditions in all air samples up to 7 m away from the source, but decreased in magnitude with the distance from the source. A greater fraction of T4 DNA was recovered from the aerosol size fractions smaller than 1 μm than E. coli K12 at all air sampling locations. Higher efficiency HVAC filtration also reduced the amount of DNA recovered in air samples and on settle plates located 3‐7 m from the source.     

Hsp100 Molecular Chaperone ClpB and Its Role in Virulence of Bacterial Pathogens

This review focuses on the molecular chaperone ClpB that belongs to the Hsp100/Clp subfamily of the AAA+ ATPases and its biological function in selected bacterial pathogens, causing a variety of human infectious diseases, including zoonoses. It has been established that ClpB disaggregates and reactivates aggregated cellular proteins. It has been postulated that ClpB’s protein disaggregation activity supports the survival of pathogenic bacteria under host-induced stresses (e.g., high temperature and oxidative stress), which allows them to rapidly adapt to the human host and establish infection. Interestingly, ClpB may also perform other functions in pathogenic bacteria, which are required for their virulence. Since ClpB is not found in human cells, this chaperone emerges as an attractive target for novel antimicrobial therapies in combating bacterial infections.     

Efficacy of thyme oil-alginate-based coating in reducing foodborne pathogens on fresh-cut apples

In this study, the inhibition of an alginate-based edible coating (EC) containing thyme oil (0.05%, 0.35% and 0.65%) was evaluated against Listeria monocytogenes, Salmonella Typhimurium, Staphylococcus aureus and Escherichia coli O157:H7 inoculated onto fresh-cut apples. To investigate the antibacterial mechanism of thyme oil, the constituent compounds of that were analysed by gas chromatography-mass spectrometry (GC-MS), and the cellular damage of pathogens was observed by scanning electron microscopy (SEM). Results showed that alginate-based EC containing thyme oil effectively inhibited the growth of pathogens on fresh-cut apples. GC-MS analysis revealed thymol (47.23%) as the major compounds in thyme oil. SEM showed that the cell membrane of foodborne pathogens was damaged by thyme oil, causing their inactivation. Treatment with alginate-based EC containing 0.05% thyme oil preserved the sensory characteristics of fresh-cut apples. Therefore, using alginate-based EC with thyme oil may represent a potential approach to preserve and enhance the safety of fresh-cut apples.     

A comparison of saturated steam and superheated steam for inactivation of Escherichia coli O157:H7, Salmonella Typhimurium,and Listeria monocytogenes biofilms on polyvinyl chloride and stainless steel

This study was performed to compare the effectiveness of saturated steam (SS) and superheated steam (SHS) in the inactivation of Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes biofilms on polyvinyl chloride (PVC) and stainless steel. Biofilms were formed on PVC and stainless steel coupons by using a mixture of three strains each of three foodborne pathogens at 25 °C. After biofilm development, PVC and stainless steel coupons were treated with SS at 100 °C and SHS at 125, 150, 175, and 200 °C for 5, 10, 20, and 30 s on both sides. The viable cell numbers of biofilms were significantly (p < 0.05) reduced as SHS temperature and exposure time increased. For all biofilm cells, SHS treatment resulted in an additional log reduction compared to SS treatments. After exposure to 200 °C steam for 30 s or 10 s on PVC or stainless steel, respectively, the numbers of biofilm cells were reduced to below the detection limit (1.48 log). This study demonstrated that SHS treatment effectively reduced populations of biofilm cells and reduced disinfection time compared to SS treatments and further evaluated its potential as an excellent intervention for controlling microbial biofilms and enhancing safety in the food processing industry.     

Microbial benefits and risks of raw milk cheese

Consumer preference for raw milk cheese is continually growing, owing to its more intense and varied flavor than pasteurized milk cheese. Flavor development in raw milk cheese is mainly governed by its naturally existing microbial community, which also contributes to the inhibition of food-borne pathogenic bacterial growth. Lactic acid bacteria, the dominant indigenous microorganisms of raw milk cheese, produce pathogen-inhibiting substances such as bacteriocin, organic acids, and hydrogen peroxide, and it is possible to manufacture cheese with desirable microbiological qualities. Nonetheless, outbreaks of food-borne illnesses have been linked to the consumption of raw milk cheese, and concerns have been raised regarding the microbiological safety of cheese manufactured from raw milk. Consequently, efficient and accurate methods for detecting contaminated bacterial pathogens in raw milk cheese have been promptly developed, including conventional plating, PCR-based technology, and immunoassay-integrated methods. The microbiological risk of the cheese can be reduced by proper ripening processing. However, additionally, hygiene in the environments for milk production and cheesemaking and the post-manufacturing stage needs to be constantly microbiologically monitored.     

Rapid and standardized methods for detection of foodborne pathogens and mycotoxins on fresh produce

Due to the increase in consumption of fresh produce regarding to the health demand in the last decades, a considerable portion of foodborne outbreaks has been trackbacked to contaminated fresh produce, which have appeared as highly possible vehicles for foodborne outbreaks nowadays. Delays in detection of pathogens and mycotoxins on fresh produce hindered the trace-back investigations in finding the source and revealed the urgent need of rapid and reliable methods. In the frame of this review, we summarized available fast, reliable and standardized methods (conventional, molecular, rapid and recently developed methods) used for detection of the most common foodborne pathogens and mycotoxins which are the most likely causative agents of outbreaks caused by contaminated fresh produce.     

Assessment of foodborne pathogen presence in the peach supply chain and its potential risk to the end consumer

Peaches are popular, nutritious and widely consumed. Being a tree crop, it is considered a low risk fruit, with no direct water contact, and no previous foodborne disease outbreaks associated with its consumption. However, in 2014 the pioneer association between stone fruit and a foodborne illness was reported, linking Listeria monocytogenes to stone fruit. This highlights the need for better understanding of risk associated with contaminated fresh stone fruit, in order to implement adequate preventative measures. No information is available on the presence of foodborne pathogens on peaches in the supply chain. A case study approach was therefore followed to assess foodborne pathogen presence on the farm, focusing on the impact of irrigation water, facility sanitation and hygiene by collecting various fruit and environmental samples (n = 428). This study demonstrates the effectiveness of integrating basic microbial testing with safety management and risk assessment tools that can be collectively used to improve the food safety management system. No Salmonella Typhimurium was detected from samples, however, Escherichia coli O157:H7, Listeria spp. and Staphylococcus aureus were detected on fruit and environmental samples. Despite the GlobalG.A.P. certification status of the farm, livestock frequented water sources which lead to E. coli O157:H7 contamination. This conclusion was based on positive detection of foodborne pathogens from the water sources and subsequent removal of livestock which resulted in a definite decrease in pathogen detection. A number of E. coli O157:H7 and S. aureus were detected during the second year of monitoring from environmental samples and it was observed that the personal hygiene and facility sanitation was not adequately enforced. Based on feedback given to the farmer, enforcement was improved and a definite decrease in foodborne pathogens was observed in the following sampling cycle. Areas of risk that were still identified following the fourth year of monitoring included the water source used for irrigation and poor sanitation in the production and processing facilities. Limited foodborne pathogen prevalence on peaches over the full study period as well as the extended export supply chain at controlled temperatures resulted in low-to-medium calculated consumer risk. The correct and meticulous implementation of integrated and holistic pre- and post-harvest food safety management systems is therefore essential to prevent produce contamination, reduce the consumer risk and therefore ensure overall product safety.     

Estimated exposure to hepatitis E virus through consumption of swine liver and liver sausages

A quantitative risk assessment was undertaken following the Codex Alimentarius principles in order to predict the exposure of consumers to hepatitis E virus (HEV) through food consumption. Taking into account the tropism of HEV, fresh liver and liver sausages were regarded as having a higher risk of contamination. The model entailed a hypothetical food pathway and was based on worst case scenario where the intake of contaminated food derived from a 100% HEV-infected pig population was estimated. As no data on the prevalence of infectious HEV was available, the HEV-RNA prevalence in food matrices and the seroprevalence of HEV-specific antibodies in swine were assessed and adjusted for diagnostic misclassification and sampling uncertainty. Considering a HEV prevalence of 100% in pigs and excluding further cross-contamination events, a food portion consisting of 130 gr of liver or of 32.5 gr of sausage (containing 30% of liver) yielded an estimated exposure of 8047 and 210 RNA copies (median values), respectively. These findings take into account the effect of thermal treatment on the HEV-RNA concentration of food. Due to the lack of information concerning the correlation between HEV-RNA concentration and the amount of infectious virus as well as the dose-response relationship of HEV, the calculated RNA copies do not allow direct conclusions to be drawn on the risk of infection following ingestion of these food types. The true prevalence was estimated for Switzerland and Germany, leading to an overall prevalence of HEV-RNA in food of 6.2% (90% Highest Density Intervals (HDIs): 2.5%–11.2%). In comparison with fresh liver, liver sausages showed a higher prevalence, most likely due to the presence of more than one liver within the same sausage. The true prevalence of anti-HEV IgG ranged between 59.4% (HDIs 56.5%–62.4%) and 62.6% (HDIs 58.8%–64.3%) and between 7.6% (HDIs 3.3%–13.2%) and 30.5% (HDIs 23.2%–38.2%) in pigs and wild boars, respectively. The high prevalence of antibodies support the evidence that these animals can act as reservoirs for HEV and can contribute epidemiologically to the maintenance of the virus in the surroundings. This study is a preliminary investigation and highlights the major existing gaps needed to be filled in order to enable a refined HEV risk assessment that can drive future decisions for the implementation of food safety and of control measures.