Outbreaks Of Foodborne Pathogens Research Articles

Development of Predictive Modeling for Removal of Multispecies Biofilms of Salmonella Enteritidis, Escherichia coli, and Campylobacter jejuni from Poultry Slaughterhouse Surfaces.

Salmonella Enteritidis, Escherichia coli, and Campylobacter jejuni are among the most common foodborne pathogens worldwide, and poultry products are strongly associated with foodborne pathogen outbreaks. These pathogens are capable of producing biofilms on several surfaces used in the food processing industry, including polyethylene and stainless steel. However, studies on multi-species biofilms are rare. Therefore, this study aimed to develop predictive mathematical models to simulate the adhesion and removal of multispecies biofilms. All combinations of microorganisms resulted in biofilm formation with differences in bacterial counts. E. coli showed the greatest ability to adhere to both surfaces, followed by S. Enteritidis and C. jejuni. The incubation time and temperature did not influence adhesion. Biofilm removal was effective with citric acid and benzalkonium chloride but not with rhamnolipid. Among the generated models, 46 presented a significant coefficient of determination (R2), with the highest R2 being 0.88. These results provide support for the poultry industry in creating biofilm control and eradication programs to avoid the risk of contamination of poultry meat.

Surveillance and source tracking of foodborne pathogens in the vegetable production systems of India

Fresh vegetables are prone to foodborne pathogen infection due to improper cultivation methods and poor post-harvest handling practices. This paper describes the prevalence of foodborne pathogens in three vegetables (tomato, brinjal, and lablab) cultivated by small-scale producers (SSP) of India. We assessed the possible entry of pathogens into the vegetable production chain. Samples from soil, manure, irrigation water, harvesting bins, and workers’ hands were assessed as sources of possible pathogen entry. In addition, further sampling was done to determine prevalence of these pathogens in the produce from the agricultural fields and markets. Total plate counts, yeast and mold count, total coliforms like general microbial indices, and possible foodborne pathogens like Salmonella, Escherichia coli O157, Staphylococcus aureus, Pseudomonas aeruginosa, and norovirus were assessed in all the samples by standard microbiological, biochemical, and molecular methods. The results revealed that among the three vegetables we studied, brinjal had the highest load of general microbial indicators. Moreover, the total coliforms count of market vegetables was higher than that of on-farm vegetables, indicating poor hygiene in post-harvest operations. The pathogen Pseudomonas aeruginosa was found in the market tomatoes (0.35 log10 cfu/g), and E. coli was detected in the market samples of brinjal (2.98–3.89 log10 cfu/g) and lablab (0.59–2.21 log10 cfu/g), thereby revealing fecal cross-contamination during pre or post-harvest operations. None of the vegetable samples were contaminated with E. coli O157:H7, Staphylococcus aureus, Salmonella sp., and norovirus. However, the microbiological source tracking of primary production farms showed that E. coli O157:H7 was present in manure (9/27), soil (6/27), harvest bins (6/27), and irrigation water samples (3/27) of SSP farms. In addition, soil (33%), manure (11%), and harvest bins (11%) had Pseudomonas aeruginosa. In conclusion, our study suggests that adequate knowledge of good agricultural practices for small-scale producers to cultivate microbiologically safe vegetable production and proper handling strategies for vegetable vendors is crucial to mitigate foodborne pathogen outbreaks through fresh vegetables.

Serovar-level identification of bacterial foodborne pathogens from full-length 16S rRNA gene sequencing.

The resolution of variation within species is critical for interpreting and acting on many microbial measurements. In the key foodborne pathogens Salmonella and Escherichia coli, the primary subspecies classification scheme used is serotyping: differentiating variants within these species by surface antigen profiles. Serotype prediction from whole-genome sequencing (WGS) of isolates is now seen as comparable or preferable to traditional laboratory methods where WGS is available. However, laboratory and WGS methods depend on an isolation step that is time-consuming and incompletely represents the sample when multiple strains are present. Community sequencing approaches that skip the isolation step are, therefore, of interest for pathogen surveillance. Here, we evaluated the viability of amplicon sequencing of the full-length 16S rRNA gene for serotyping Salmonella enterica and E. coli. We developed a novel algorithm for serotype prediction, implemented as an R package (Seroplacer), which takes as input full-length 16S rRNA gene sequences and outputs serovar predictions after phylogenetic placement into a reference phylogeny. We achieved over 89% accuracy in predicting Salmonella serotypes on in silico test data and identified key pathogenic serovars of Salmonella and E. coli in isolate and environmental test samples. Although serotype prediction from 16S rRNA gene sequences is not as accurate as serotype prediction from WGS of isolates, the potential to identify dangerous serovars directly from amplicon sequencing of environmental samples is intriguing for pathogen surveillance. The capabilities developed here are also broadly relevant to other applications where intraspecies variation and direct sequencing from environmental samples could be valuable.IMPORTANCEIn order to prevent and stop outbreaks of foodborne pathogens, it is important that we can detect when pathogenic bacteria are present in a food or food-associated site and identify connections between specific pathogenic bacteria present in different samples. In this work, we develop a new computational technology that allows the important foodborne pathogens Escherichia coli and Salmonella enterica to be serotyped (a subspecies level classification) from sequencing of a single-marker gene, and the 16S rRNA gene often used to surveil bacterial communities. Our results suggest current limitations to serotyping from 16S rRNA gene sequencing alone but set the stage for further progress that we consider likely given the rapid advance in the long-read sequencing technologies and genomic databases our work leverages. If this research direction succeeds, it could enable better detection of foodborne pathogens before they reach the public and speed the resolution of foodborne pathogen outbreaks.

Unveiling the gender gap in research: a bibliometric analysis of the 100 most-cited articles on food-borne pathogen outbreaks from 1990 to 2020.

Despite a recent increase in the representation of female authors in scientific literature, a significant gap persists concerning the inclusion of women in research. This necessitates the analysis of published literature from a gender perspective. This study aimed to provide gender distribution in authorship in the 100 most-cited articles on food-borne pathogen outbreaks from 1990 to 2020. Bibliometric analysis was conducted using the Scopus database. Two reviewers were selected to search the database. We included the 100 most-cited articles on foodborne outbreak investigations. The analysis was conducted using Statistical Package for Social Sciences (SPSS) version 26 and Microsoft Excel version 2016. The citation data, including total citations, citations per year, and representation of women as first and senior authors, was analyzed in terms of frequencies, mean, median, and interquartile range. The correlation between journal impact factor and the representation of women in high-impact factor journals was determined. A p-value of <0.05 was considered significant. Most of the top-cited articles were published between 2001 and 2010 (n=47). The top 3 most-cited articles were from the USA. Of the total 100 articles, women were the first and last authors in 46% and 28% of the articles, respectively, reflecting a significant gender gap. However, the proportion of females as principal investigators gradually increased from 25% (n=10/30) to 52% (n=24/47) during the period 2001-2010 and to 92% (n=12/13) during 2011-2020. The USA had the highest number of included articles (n=48), and women were principal authors in 56% (n=27) of them. The lowest representation of women was observed in Austria, Denmark, Japan, Netherlands, New Zealand, Nigeria, Portugal, and the United Kingdom. Women are under-represented in published literature on food-borne pathogen outbreaks. Although the representation of women as principal authors has recently increased, disparities still exist at the senior-author level, calling for women's advancement in academic science.

Novel next generation sequencing panel method for the multiple detection and identification of foodborne pathogens in agricultural wastewater.

Detecting and identifying the origins of foodborne pathogen outbreaks is a challenging. The Next-Generation Sequencing (NGS) panel method offers a potential solution by enabling efficient screening and identification of various bacteria in one reaction. In this study, new NGS panel primer sets that target 18 specific virulence factor genes from six target pathogens (Bacillus cereus, Yersinia enterocolitica, Staphylococcus aureus, Vibrio cholerae, Vibrio parahaemolyticus, and Vibrio vulnificus) were developed and optimized. The primer sets were validated for specificity and selectivity through singleplex PCR, confirming the expected amplicon size. Crosscheck and multiplex PCR showed no interference in the primer set or pathogenic DNA mixture. The NGS panel analysis of spiked water samples detected all 18 target genes in a single reaction, with pathogen concentrations ranging from 108 to 105 colony-forming units (CFUs) per target pathogen. Notably, the total sequence read counts from the virulence factor genes showed a positive association with the CFUs per target pathogen. However, the method exhibited relatively low sensitivity and occasional false positive results at low pathogen concentrations of 105 CFUs. To validate the detection and identification results, two sets of quantitative real-time PCR (qPCR) analyses were independently performed on the same spiked water samples, yielding almost the same efficiency and specificity compared to the NGS panel analysis. Comparative statistical analysis and Spearman correlation analysis further supported the similarity of the results by showing a negative association between the NGS panel sequence read counts and qPCR cycle threshold (Ct) values. To enhance NGS panel analysis for better detection, optimization of primer sets and real-time NGS sequencing technology are essential. Nonetheless, this study provides valuable insights into applying NGS panel analysis for multiple foodborne pathogen detection, emphasizing its potential in ensuring food safety.

Tunable Magneto-Plasmonic Nanosensor for Sensitive Detection of Foodborne Pathogens.

Frequent outbreaks of food-borne pathogens, particularly E. coli O157:H7, continue to impact human health and the agricultural economy tremendously. The required cell count for this pathogenic strain of E. coli O157:H7 is relatively low and hence it is vital to detect at low colony forming unit (CFU) counts. Available detection methods, though sensitive, fall short in terms of timeliness and often require extensive sample processing. To overcome these limitations, we propose a novel magneto-plasmonic nanosensor (MPnS) by integrating surface plasmon resonance (SPR) properties with spin-spin magnetic relaxation (T2 MR) technology. We engineered MPnS by encapsulating several gold nanoparticles (GNPs) within the polymer-coating of iron oxide nanoparticles (IONPs). First, the polyacrylic acid (PAA)-coated IONPs were synthesized using a solvent precipitation method, then gold chloride solution was used to synthesize GNPs and encapsulate them within the PAA-coatings of IONPs in one step. A magnetic separation technique was used to purify the MPnS and the presence of GNPs within IONPs was characterized using transmission electron microscopy (TEM), energy dispersive x-ray spectroscopy (EDS), and other spectroscopic methods. The synthesized MPnS exhibits MR relaxation properties while possessing amplified optical properties than conventional GNPs. This allows for rapid and ultrasensitive detection of E. coli O157:H7 by SPR, T2 MR, and colorimetric readout. Experiments conducted in simple buffer and in milk as a complex media demonstrated that our MPnS-based assay could detect as low as 10 CFUs of this pathogenic strain of E. coli O157:H7 in minutes with no cross-reactivity. Overall, the formulated MPnS is robust and holds great potential for the ultrasensitive detection of E. coli O157:H7 in a simple and timely fashion. Moreover, this platform is highly customizable and can be used for the detection of other foodborne pathogens.

Microfluidic Sampling and Biosensing Systems for Foodborne Escherichia coli and Salmonella.

Developments of portable biosensors for field-deployable detections have been increasingly important to control foodborne pathogens in regulatory environment and in early stage of outbreaks. Conventional cultivation and gene amplification methods require sophisticated instruments and highly skilled professionals; while portable biosensing devices provide more freedom for rapid detections not only in research laboratories but also in the field; however, their sensitivity and specificity are limited. Microfluidic methods have the advantage of miniaturizing instrumental size while integrating multiple functions and high-throughput capability into one streamlined system at low cost. Minimal sample consumption is another advantage to detect samples in different sizes and concentrations, which is important for the close monitoring of pathogens at consumer end. They improve measurement or manipulation of bacteria by increasing the ratio of functional interface of the device to the targeted biospecies and in turn reducing background interference. This article introduces the major active and passive microfluidic devices that have been used for bacteria sampling and biosensing. The emphasis is on particle-based sorting/enrichment methods with or without external physical fields applied to the microfluidic devices and on various biosensing applications reported for bacteria sampling. Three major fabrication methods for microfluidics are briefly discussed with their advantages and limitations. The applications of these active and passive microfluidic sampling methods in the past 5 years have been summarized, with the focus on Escherichia coli and Salmonella. The current challenges to microfluidic bacteria sampling are caused by the small size and nonspherical shape of various bacterial cells, which can induce unpredictable deviations in sampling and biosensing processes. Future studies are needed to develop rapid prototyping methods for device manufacturing, which can facilitate rapid response to various foodborne pathogen outbreaks.

Formation of Oleic Acid Chlorohydrins in Vegetables during Postharvest Chlorine Disinfection.

High chlorine doses (50-200 mg/L) are used in postharvest washing facilities to control foodborne pathogen outbreaks. However, chlorine can react with biopolymers (e.g., lipids) within the produce to form chlorinated byproducts that remain in the food. During chlorination of micelles of oleic acid, an 18-carbon alkene fatty acid, chlorine added rapidly across the double bond to form the two 9,10-chlorohydrin isomers at a 100% yield. The molar conversion of lipid-bound oleic acid to 9,10-chlorohydrins in chlorine-treated glyceryl trioleate and produce was much lower, reflecting the restricted access of chlorine to lipids. Yields from spinach treated with 100 mg/L chlorine at 7.5 °C for 2 min increased from 0.05% (0.9 nmol/g-spinach) for whole leaf spinach to 0.11% (2 nmol/g) when shredding increased chlorine access. Increasing temperature (21 °C) and chlorine contact time (15 min) increased yields from shredded spinach to 0.83% (22 nmol/g) at 100 mg/L chlorine and to 1.8% (53 nmol/g) for 200 mg/L chlorine. Oleic acid 9,10-chlorohydrin concentrations were 2.4-2.7 nmol/g for chlorine-treated (100 mg/L chlorine at 7.5 °C for 2 min) broccoli, carrots, and butterhead lettuce, but 0.5-1 nmol/g for cabbage, kale, and red leaf lettuce. Protein-bound chlorotyrosine formation was higher in the same vegetables (5-32 nmol/g). The Chinese hamster ovary cell chronic cytotoxicity LC50 value for oleic acid 9,10-chlorohydrins was 0.106 mM. The cytotoxicity associated with the chlorohydrins and chlorotyrosines in low masses (9-52 g) of chlorine-washed vegetables would be comparable to that associated with trihalomethanes and haloacetic acids at levels of regulatory concern in drinking water.

Antimicrobial nanoparticles and biodegradable polymer composites for active food packaging applications.

The food industry faces numerous challenges to assure provision of tasty and convenient food that possesses extended shelf life and shows long-term high-quality preservation. Research and development of antimicrobial materials for food applications have provided active antibacterial packaging technologies that are able to meet these challenges. Furthermore, consumers expect and demand sustainable packaging materials that would reduce environmental problems associated with plastic waste. In this review, we discuss antimicrobial composite materials for active food packaging applications that combine highly efficient antibacterial nanoparticles (i.e., metal, metal oxide, mesoporous silica and graphene-based nanomaterials) with biodegradable and environmentally friendly green polymers (i.e., gelatin, alginate, cellulose, and chitosan) obtained from plants, bacteria, and animals. In addition, innovative syntheses and processing techniques used to obtain active and safe packaging are showcased. Implementation of such green active packaging can significantly reduce the risk of foodborne pathogen outbreaks, improve food safety and quality, and minimize product losses, while reducing waste and maintaining sustainability.

Development of an Enteric Bacterial Enrichment Broth and Its Performance for Isolation of Clinically Significant Bacterial Pathogens from Stool

Background: Early detection and accurate identification of foodborne pathogen outbreaks is an important public health function. Increased clinical adoption of multiplex PCR assays or culture independent diagnostic tests (CIDT) correlates to more stool specimens sent to public health laboratories (PHL) for characterization. Isolation and confirmation of enteric bacterial pathogens can prove difficult to consistently recover. The purpose of this study was to evaluate the performance of a broad-use laboratory developed enrichment broth for isolation of Campylobacter, Salmonella, Shigella, and Yersinia strains from stool specimens. Methods: The study compared differences in positivity rates among media and enrichment combinations at specific time points. Comparison of direct inoculation (DI), enrichment using a lab-developed Enteric Bacterial Enrichment (EBE) broth and gold-standard isolation methods were conducted to test current utility of this established practice with stool specimens heat injured and non-injured. Results: A total of 234 spiked stool samples, 175 non-injured and 59 heat injured, were tested with varying bacterial concentrations. For non-injured stools, direct inoculation performed better for Campylobacter and Yersinia than enrichment. Conversely, Salmonella and Shigella recovery and limit of detection increased with enrichment. Campylobacter had the highest percent recovery while Shigella being the lowest from direct plating at 6-hour and 24-hour enrichment periods. Among broths, EBE performed the best for Yersinia and similar to Selenite broth for Salmonella and Shigella. Generally, heat injured stool had a significantly lower percent of recovery than non-heat injured with a higher limit of detection across organisms. Conclusion: Our data suggest there is an only utility for targeted enrichment of CIDT positive Salmonella stool specimens. We highlight the difficulties of formulating an enrichment broth capable of supporting a variety of enteric pathogens with standardized incubation. Increasing demands on PHL infrastructure warrant further examination of enhancing organism isolation and cost analyses for CIDT positive specimens.

The Role of Peridomestic Rodents as Reservoirs for Zoonotic Foodborne Pathogens.

Although rodents are well-known reservoirs and vectors for a number of zoonoses, the functional role that peridomestic rodents serve in the amplification and transmission of foodborne pathogens is likely underappreciated. Clear links have been identified between commensal rodents and outbreaks of foodborne pathogens throughout Europe and Asia; however, comparatively little research has been devoted to studying this relationship in the United States. In particular, regional studies focused on specific rodent species and their foodborne pathogen reservoir status across the diverse agricultural landscapes of the United States are lacking. We posit that both native and invasive species of rodents associated with food-production pipelines are likely sources of seasonal outbreaks of foodborne pathogens throughout the United States. In this study, we review the evidence that identifies peridomestic rodents as reservoirs for foodborne pathogens, and we call for novel research focused on the metagenomic communities residing at the rodent-agriculture interface. Such data will likely result in the identification of new reservoirs for foodborne pathogens and species-specific demographic traits that might underlie seasonal enteric disease outbreaks. Moreover, we anticipate that a One Health metagenomic research approach will result in the discovery of new strains of zoonotic pathogens circulating in peridomestic rodents. Data resulting from such research efforts would directly inform and improve upon biosecurity efforts, ultimately serving to protect our food supply.

Label-Free Immunoassay for Multiplex Detections of Foodborne Bacteria in Chicken Carcass Rinse with Surface Plasmon Resonance Imaging.

The frequent outbreaks of foodborne pathogens have stimulated the demand of biosensors capable of rapid and multiplex detection of contaminated food. In this study, surface plasmon resonance imaging (SPRi) was used in simultaneous label-free detection of multiple foodborne pathogens, mainly Salmonella spp. and Shiga-toxin producing Escherichia coli (STEC), in commercial chicken carcass rinse. The antibodies were immobilized on the same SPRi sensor chip as a label-free immunoassay. Their immobilization concentrations were optimized to be ranging from 0.25 to 1.0 mg/mL, and independent of pH values. This label-free immunoassay achieved 106 colony-forming unit (CFU)/mL limit of detection for Salmonella, which was further improved to 1.0 CFU/mL with overnight bacteria enrichment. The injected samples with different bacteria, Salmonella Enteritidis, STEC, and Listeria monocytogenes, have been identified by the same biochip. Moreover, the SPRi signals revealed complex interference effects among coexisting bacteria species in heterogeneous bacteria solutions. This SPRi-based immunoassay demonstrates the great potential in high-throughput screening of multiple pathogenic bacteria coexisting in chicken carcass rinse. The reliability of antibody immobilization and cross-reactions of different antibodies on the same biochip are the major challenges of practical application of SPRi.

When Pet Snacks Look Like Children's Toys! The Potential Role of Pet Snacks in Transmission of Bacterial Zoonotic Pathogens in the Household.

Recent foodborne pathogen outbreaks associated with dry pet food and treats have focused the attention on these products as vehicles of pathogens for both pets and their owners. This study investigates the purchasing habits of dog owners and determines if and in what form pet snacks can be potentially dangerous for humans, especially for children. For these purposes, questionnaires collected from 406 dog owners were evaluated and microbiological analyses were performed on 120 dry pet snacks. The shape of the pet snack affects the purchase (median score, Mdn = 6.4) and the star bone was the preferred one (Mdn = 7.1). Most of the participants (76.0%; p < 0.001) stated that snacks are attractive to their children and that the possibility for children to get in contact with pet snacks is rare, but not implausible (Mdn = 3.1). Indeed, more than 6% of respondents admitted that there had been incidents of involuntary ingestion of pet snacks, with fever and gastrointestinal manifestations. Microbiological analyses showed that 119 dry pet snacks analyzed of a total of 120 (99.2%) were in good sanitary condition except for one sample where the presence of Listeria ivanovii was confirmed. The upward trend in the presence of pets in households and the strong and continuous growth in value and volume of the pet food market led researchers to analyze possible public health issues. Children and infants in particular are the most exposed subjects as they are more likely to come into contact with pet snacks, attracted by a shape similar to that of a toy. For this reason, although our findings did not highlight important microbiological contamination of pet snacks, it would be useful to standardize food safety criteria with those for human food from a One Health perspective.

A Visual and Sensitive Detection of Escherichia coli Based on Aptamer and Peroxidase-like Mimics of Copper-Metal Organic Framework Nanoparticles

In order to monitor and respond rapidly to outbreaks of food-borne pathogens, establishing rapid and sensitive detection methods is becoming increasingly urgent. In this work, through the synthesis of copper-based metal-organic framework nanoparticles (Cu-MOF NPs) and functionalized with aptamers, we developed a colorimetric protocol to detect Escherichia coli. In a typical experimental procedure, aptamer 1 was immobilized onto microplate to act as capture probes. Cu-MOF NPs were synthesized and functionalized with streptavidin and biotinylated aptamer 2 to form the signal probes. In the presence of E. coli, aptamers on both capture and signal probes bind with E. coli and form a sandwich-type complex. The Cu-MOF NPs enable to catalyze the colorless peroxidase substrate to yield a colorimetric output signal. This peroxidase-like mimics-based colorimetric aptasensor showed a rapid and sensitive quantification of E. coli in the concentration range of 16~1.6 × 106 cfu/mL with a limit of quantitation (LOQ) of 16 cfu/mL and limit of detection (LOD) of 2 cfu/mL. The application of the developed assay for colorimetric measuring of milk samples was evaluated with satisfactory results. The developed Cu-MOF NPs-assisted visual method can be expected as a powerful alternative and promising tool for foodborne pathogen detection and control.

The Influences of Organic Matter Concentrations in Juices for Pathogen Detection Using Phage-Based Biosensors

Fruit and vegetables are playing an important role of today’s healthy diet. Juices are the liquid extracts from fruit and vegetables, which contain lots of organic matters, such as vitamins, minerals and plant chemicals (phytonutrients). Commercial bottle juices usually contain different percentages of real juices in their juice products. Therefore, the amount of organic matter content in juices are different in various brands of juices. The foodborne pathogen outbreaks through the consumption of fruit or vegetable juices continue to be reported (CDC, 2016). It indicates that pathogens like Salmonella can be packaged with juices even with current manufacture microbial-inactivation process. According to several studies, the acidity in tomatoes juice and the phyto-chemicals (like chlorophyll) from damage leaves in leafy greens samples can affect the sensitivity of pathogen detection in juices. For example, chlorophyll is one of the substances in leafy green juice that inhibits PCR reaction for pathogen detection. This made the pathogen detection in some juices a difficult task to achieve. The phage magnetoelastic (ME) biosensors are wireless sensors, whose resonance oscillation and resonance frequency are actuated and detected through magnetic fields. These biosensors have been shown to be highly sensitive and specific in pathogen detection including Salmonella on various food surfaces or liquids (Li et al., 2010). Therefore, in this study, different concentrations of juices from tomatoes and spinach with artificially spiked Salmonella (at the concentration of 104 cfu/ml) was tested by ME biosensors. The influence of pathogen detection capability was then studied by comparing the bacterial capture rates on biosensors. In tomato juice, the results showed that the capture rate of Salmonella can be reached up to 90.68% by using 100 ME biosensors in a tube rocking experiment with 10% tomato juice content. In spinach juice, the capture rate of Salmonella showed similar results as 90.68% in the same 10% juice concentration. However, when the juice concentration of spinach went up to 15% and 20%, the bacterial capture rate slightly decreased. The Salmonella capture rate were shown as 89.82% and 89.065, respectively. The decreasing of capture rate was obvious by using 50 ME sensors for the 15% and 20% spinach juices. In conclusion, by using 100 phage ME biosensors, the detection platform can detect as high as 89% Salmonella in high juice concentration (15 % and 20%) of both tomato and spinach juice samples. While in the moderate juice concentration zone (5-10%), the ME biosensors show very promising results of detecting 90% Salmonella in both juices.

In vitro and in vivo characterisation of Listeria monocytogenes outbreak isolates

Listeriosis is an important food-borne disease responsible for high rates of morbidity and mortality. L. monocytogenes has been the cause of several foodborne outbreaks and its ability to adapt and survive in a wide range of environmental conditions makes eradication difficult. Many L. monocytogenes strains are avirulent but have the ability to increase their virulence if exposed to environmental stresses. The aim of this study was to explain the observed increase in virulence of outbreak L. monocytogenes isolates by using phenotypic assays and whole genome sequencing. Four L. monocytogenes isolates from sweetcorn and one isolate from a raw milk (control) were sequenced and characterised using a range of phenotypic assays. The four L. monocytogenes sweetcorn isolates displayed a significant increase for in vitro adhesion and invasion of epithelial cells compared to the control isolate. They also showed a higher level of colonisation of the liver and spleen in vivo. In addition, the four L. monocytogenes isolates displayed an increased ability to form biofilms, resist heat stress and resist a combination of antimicrobials. Investigation of the genomes of the four L. monocytogenes sweet corn isolates identified Single Nucleotide Polymorphisms (SNPs) in genes, which may have a role in the observed phenotypes characteristic of these strains, particularly in response to survival properties within the environment or in terms of virulence. We highlight the importance of combining whole genomic sequencing with phenotypic characterisation as a key element in the investigation of outbreaks of foodborne pathogens.

Cost estimation of listeriosis (Listeria monocytogenes) occurrence in South Africa in 2017 and its food safety implications

Periodic outbreaks of foodborne pathogens have resulted in food safety concerns, due to health implications and cost consequences. Occurrence of Listeria monocytogenes in foods and listeriosis have been reported in developed countries; however, documentation of listeriosis in South Africa is limited. In 2017–2018, Listeria was reported on polony (processed deli meat) and listeriosis was observed in South Africa (L. monocytogenes sequence type 6 (ST-6) was identified as the causal agent for listeriosis). Due to its potential effects, we conducted cost estimates to assess the implications of listeriosis outbreak with respect to illnesses, hospitalizations and deaths, and productivity losses. Cost estimates were computed on publicly available data by using USDA-ERS cost computation model for Listeria. Listeriosis had significant impacts, as mortality of 204 individuals with confirmed listeriosis cases was reported, with infants having the highest percent of fatalities (42%). The cost valuation of fatality cases was over US$ 260 million. Hospitalization costs associated with one-month recovery from listeriosis were estimated at US$ 10.4 million. Productivity losses attributed to listeriosis for humans and export value losses for food processors were in excess of US$ 15 million. Increase of food safety measures in South Africa could reduce foodborne disease outbreaks. Pre-emptive pathogen detection, sanitary procedures and bacterial inactivation can enhance control of L. monocytogenes in food processing environments.

Strategies to reduce microbial risk and improve quality of fresh and processed strawberries: A review

Strawberries are one of the most important fruits in the Mediterranean diet and have been widely investigated for their nutritional and nutraceutical properties. Concern about the safety of fresh and processed strawberries has increased in recent years due to the emergence of several outbreaks of foodborne pathogens linked to their consumption. The use of chlorine as a disinfectant has been identified as a concern due to public health issues and limited efficacy at removing contamination, and preventing cross-contamination. This has led to the development of novel alternatives to chlorine disinfection and thermal treatments, which include, among others, the use of organic acids, high pressure processing, intense pulsed light, or pulsed electric fields. These technologies do not generally affect the nutritional and organoleptic properties of the product and some of these have been reported to stimulate the production of valuable compounds in strawberries and to improve their overall quality.

Combination Effect of High-Pressure Processing and Essential Oil (Melissa officinalis Extracts) or Their Constituents for the Inactivation of Escherichia coli in Ground Beef

The inactivation of a five-strain cocktail of Escherichia coli by high-pressure processing (HPP) and Melissa officinalis leaf extracts (MoEOs) or their similar chemical constituents (CCs; citral, geraniol, β-caryophyllene or a mixture) in fresh ground beef was investigated. The pathogenic bacteria post-process growth and survival were further determined at 4 °C, 7 days storage. Ground beef pressurized at 300, 350, and 400 MPa for 15 min in combination with 0.5 and 1.0% of MoEOs or CCs was investigated. A 5-log CFU/g reduction was achieved with properly selected pressure and MoEOs, CCs, or MIX [a reconstituted mixture of 1/3 citral, 1/3 geraniol, and 1/3 β-caryophyllene (weight basis)] concentration. Without the HPP, the inactivation potential of citral, geraniol, MoEOs, or MIX was similar and negligible, while under pressure, the inactivation potential increased significantly as the pressure and concentration increased. The Escherichia coli strains tested include Shiga toxin-producing E. coli (STEC) O157, O111, O121, O128, and O145, which are involved in many food-borne pathogen outbreaks worldwide. For 24 h under refrigeration, 1.0% citral, 1.0% geraniol, 1.0% MIX, and 1.0% MoEOs with 350 and 400 MPa could reduce ca. 3–6 log CFU/g of E. coli. The inactivation potential continued to show effectiveness during the low-temperature storage test (e.g., 4 °C, 7 days). In conclusion, the combination treatment of HPP and M. officinalis extracts was found to be significantly effective in the inactivation of E. coli. Transmission electron microscope (TEM) images further demonstrated the cell structure damaged under HPP and antimicrobial compound stresses.

Electrodeposition of a magnetic and redox-active chitosan film for capturing and sensing metabolic active bacteria

Rapid and portable detection of viable pathogen is highly desired to minimize the risk of foodborne pathogen outbreaks. Here we report a proof-of-concept fabrication methodology of a multifunctional film that allows established methods from bacterial recognition (antibodies) and nanotechnology (magnetic nanoparticles) to be coupled with electrochemical signal processing methods for detection of viable bacteria. Specifically, we enlist a sequence of externally applied electrical and magnetic signals to: i) guide the self-assembly of stimuli-responsive biopolymer; ii) incorporate magnetic nanoparticles to form a magnetic layer; iii) electro-synthesize a signal processing layer (redox-capacitor). The function of the magnetic layer is collecting and concentrating MMP-bacteria through magnetic attractions between MMP-bacteria and the magnetic layer. The function of the signal processing layer is amplifying electrochemical detection of the collected bacteria by engaging the redox-active mediators with the redox capacitor. Importantly, the fabrication demonstrated here is simple, controllable, and reagentless.