Added insult to injury? The response of meat-associated pathogens to proposed antimicrobial interventions.

Modern requirements for 'green label' meat products have led to the design of novel antimicrobial innovations which prioritise quality, safety and longevity. Plasma-functionalised water (PFW), ultraviolet light and natural antimicrobial compositions have been investigated and optimised for control of foodborne pathogens like Campylobacter jejuni and Salmonella enterica serovar Typhimurium. However, given the adaptive mechanisms present in bacteria under external stresses, it is imperative to understand the effect that sublethal treatment may have on the bacterial transcriptome. In this study, Salmonella Typhimurium and C. jejuni were treated with sublethal doses of ultraviolet light, a citrus juice/essential oil marinade, and 'spark' or 'glow' cold plasma generation system-produced PFW. Immediately after treatment, cells were lysed and RNA was extracted and purified. mRNA was converted to cDNA by reverse transcription-PCR and sequenced by an Illumina MiSeq® system. Sequences were filtered and analysed using the Tuxedo workflow. Sublethal treatment of Campylobacter jejuni and Salmonella Typhimurium led to increased immediate cellular and metabolic activity, as well as diversification in protein and metabolic functioning. There was further expression of pathogenesis and virulence-associated traits associated with spark PFW and marinade treatment of Salmonella Typhimurium. However, similar concerns were not raised with glow PFW or UV-treated samples. This study provides science-based evidence of the efficacy of multi-hurdle antimicrobial system using green-label marinades and PFW or UV to inactivate pathogens without upregulating virulence traits in surviving cells. This study will inform policymakers and food industry stakeholders and reinforces the need to incorporate in-line novel technologies to ensure consumer safety. KEY POINTS: • Salmonella and C. jejuni showed increased cell activity in immediate response to stress. • Virulence genes showed increased expression when treated with natural antimicrobials and sPFW. • Reduced immediate transcriptomic response to gPFW and UV treatment indicates lower risk.

A Small Study on Clostridioides difficile in Spinach Field Soil and the Chemical and Microbial Factors that may Influence Prevalence.

Clostridioides difficile is a human pathogen that is ubiquitous in soil. Despite increasing infection rates and evidence of foodborne transmission, there is limited data on prevalence in soil or which factors influence persistence. The aim of this study was to investigate the prevalence of these bacteria in soil from three different spinach fields and to examine the chemical composition (carbon, organic carbon, nitrogen, organic matter, minerals and pH) and microbiota to gain insight into the factors that may promote/inhibit C. difficile. The overall C. difficile prevalence (10%) was lower than expected (based on international studies) and a significantly (P < 0.05) higher prevalence was obtained in Field 3 (20%) as compared to Fields 1 and 2 (5% each). Analysis of the soil suggested that the pH as well as organic matter, calcium and phosphorus content directly and indirectly (via the microbiota) influenced the prevalence of C. difficile in adjacent fields, where other factors (eg. climate) are similar. Although further studies are required to validate our findings, the data provides the first step in developing potential soil based control strategies.

The effect of cold storage and cooking on the viability of Clostridioides difficile spores in consumer foods.

The increased detection of clinical cases of Clostridioides difficile coupled with the persistence of clostridial spores at various stages along the food chain suggest that this pathogen may be foodborne. This study examined C. difficile (ribotypes 078 and 126) spore viability in chicken breast, beef steak, spinach leaves and cottage cheese during refrigerated (4 °C) and frozen (-20 °C) storage with and without a subsequent sous vide mild cooking (60 °C, 1 h). Spore inactivation at 80 °C in phosphate buffer solution, beef and chicken were also investigated to provide D80°C values and determine if PBS was a suitable model system for real food matrices. There was no decrease in spore concentration after chilled or frozen storage and/or sous vide cooking at 60 °C. Non-log-linear thermal inactivation was observed for both C. difficile ribotypes at 80 °C in phosphate buffer solution (PBS), beef and chicken. The predicted PBS D80°C values of 5.72±[2.90, 8.55] min and 7.50±[6.61, 8.39] min for RT078 and RT126, respectively, were in agreement with the food matrices D80°C values of 5.65 min (95% CI range from 4.29 to 8.89 min) for RT078 and 7.35 min (95% CI range from 6.81 to 7.01 min) for RT126. It was concluded that C. difficile spores survive chilled and frozen storage and mild cooking at 60 °C but may be inactivated at 80 °C. Moreover thermal inactivation in PBS was representative of that observed in real food matrices (beef and chicken).

The efficiency of UV light-emitting diodes (UV-LED) in decontaminating Campylobacter and Salmonella and natural microbiota in chicken breast, compared to a UV pilot-plant scale device.

This study investigated the combined effect of Ultraviolet (UV) light-emitting diode (LED) technology treatment with refrigerated storage of chicken breast meat over 7 days on Campylobacter jejuni, Salmonella enterica serovar Typhimurium, total viable counts (TVC) and total Enterobacteriaceae counts (TEC). An optimised UV-LED treatment at 280 nm for 6 min decreased inoculated S. Typhimurium and C. jejuni populations by 0.6-0.64 log CFU/g, and TVC and TEC population by 1-1.2 log CFU/g in chicken samples. During a 7-day storage at 4 °C, a 0.73 log reduction in C. jejuni was achieved compared with non-treated samples. Moreover, the UV-LED effectiveness to reduce TVC and TEC during refrigerated storage was compared with a conventional UV lamp and a similar efficiency was observed. The impact of UV-LED and UV lamp devices on the microbial community composition of chicken meat during storage was further examined using 16 S rRNA gene amplicon sequencing. Although similar bacterial reductions were observed for both technologies, the microbial communities were impacted differently. Treatment with the UV conventional lamp increased the proportion of Brochothrix spp. In meat samples, whilst Photobacterium spp. Levels were reduced.

Stress response modulation: the key to survival of pathogenic and spoilage bacteria during poultry processing.

The control of bacterial contaminants on meat is a key area of interest in the food industry. Bacteria are exposed to a variety of stresses during broiler processing which challenge bacterial structures and metabolic pathways causing death or sublethal injury. To counter these stresses, bacteria possess robust response systems that can induce shifts in the transcriptome and proteome to enable survival. Effective adaptive responses, such as biofilm formation, shock protein production and metabolic flexibility, require rapid induction and implementation at a cellular and community level to facilitate bacterial survival in adverse conditions. This review aims to provide an overview of the scientific literature pertaining to the regulation of complex adaptive processes used by bacteria to survive the processing environment, with particular focus on species that impact the quality and safety of poultry products like Campylobacter spp., Salmonella enterica and Pseudomonas spp.

The efficacy of organic acid, medium chain fatty acid and essential oil based broiler treatments; in vitro anti-Campylobacter jejuni activity and the effect of these chemical-based treatments on broiler performance.

AIMS: This research tested the anti-Campylobacter properties of organic acids (OA), medium chain fatty acids (MCFA) and essential oils (EO) in vitro and commenced in vivo suitability testing focused on broiler performance. METHODS AND RESULTS: Nine active compounds were tested at different concentrations and times against Campylobacter jejuni in sterile distilled water, Mueller Hinton broth and grower feed digestate (GFD). Sodium caprate (1.5%, v/v), thymol (0.25% and 2.5%, v/v), carvacrol (1.25%, v/v) and potassium sorbate (1.5%, v/v) each achieved C. jejuni reductions of ≥4.5 log10  CFU per ml in GFD, the matrix most representative of the broiler gut, after 60 s. Similar reductions were achieved after 60 min with lactic acid (1.25%, v/v), formic acid (3.1%, v/v), sodium caprylate (1.5%, v/v) and carvacrol (1.25%, v/v). However, in vivo these compounds adversely affected broiler performance, resulting in dimished water intake and reduced weight. CONCLUSIONS: OA, MFCA and EO based compounds are effective anti-Campylobacter treatments in laboratory model studies but cannot be applied in vivo. SIGNIFICANCE AND IMPACT OF THE STUDY: This study illustrates that OAs, MCFAs and EOs can achieve significant reductions in Campylobacter in vitro but identifies a major issue, inhibition of broiler performance, preventing their use in practice.

Genomic diversity, virulence and source of Campylobacter jejuni contamination in Irish poultry slaughterhouses by whole genome sequencing.

AIMS: The aim was to exploit whole genome sequencing (WGS) to assess genomic diversity, identify virulence genes and deduce the proportion of Campylobacter colonized broilers that directly contaminate their carcasses. METHODS AND RESULTS: Campylobacter jejuni isolates (107) from caeca and carcass neck skin samples (50 pairs from the same batch plus 7 individual caeca) sampled at three poultry slaughterhouses over a one-year period were selected for sequencing (MiSeq; Illumina). FastQ files were submitted to BioNumerics for analysis using the wgMLST scheme for allele calling. Campylobacter cgMLST and hierarchical clustering was performed by applying the single linkage algorithm. Sequence types (STs) were determined in silico from the WGS data and isolates were assigned into clonal complexes (CCs) using the Campylobacter PubMLST.org database. Virulence genes were determined by downloading core sequences from the virulence factor database (VFDB) and the National Center for Biotechnology Information (NCBI). A high degree of diversity was observed with 23 different STs identified. ST257 and CC-21 were the most common STs and CCs, respectively. cgMLST analysis suggested that 56% of carcass contamination was a direct result of contamination from caeca from the same batch. Virulence genes known to play a role in human C. jejuni infection were identified such as the wlaN gene and the genes associated with lipooligosaccharide synthesis, which were identified in 30% of isolates. CONCLUSIONS: Caecal colonization was the more plausible occurring source of C. jejuni contamination of broiler carcasses, compared with cross-contamination from another batch or the environment. The high rate of genetic diversity observed amongst caecal isolates is consistent with a wide variety of Campylobacter strains circulating in poultry flocks in Ireland. SIGNIFICANCE AND IMPACT OF STUDY: The results will further inform broiler processors and regulators about the influence and importance of on-farm colonization versus slaughterhouse cross-contamination and the relationship between C. jejuni in caeca and carcasses during processing.

The effect of four alternative chilling regimes on the bacterial load on beef carcasses.

The objective of this study was to compare the effect of current (10 °C for 10 h followed by 0 °C with a low fan speed) versus four alternative beef carcass chilling regimes, ranging from -6 °C to 0 °C and wind speeds between 1.5 and 6 m/s on the microbiology of beef carcasses. The temperature and relative humidity (RH) in the chillers, the carcass core and surface temperature, pH, water activity (aw) and carcass weight (drip) loss were recorded. Bacterial concentrations (total viable counts (TVC), total Enterobacteriaceae counts (TEC), Pseudomonas spp., lactic acid bacteria (LAB) and Brochothrix thermosphacta) were also monitored. Similar pH, aw and drip loss (2%) values were obtained regardless of chilling regime. For the most part, bacterial concentrations were also similar and, where statistically significant (P < 0.05) counts occurred, the reductions were low (≤1 log10 cfu/cm2). It was concluded that the current chilling regime was as effective as the tested alternatives in terms of the bacterial quality of the carcasses.

An investigation of the environmental niches of blown pack spoilage causing Clostridium estertheticum and Clostridium gasigenes on New Zealand beef and sheep farms.

The transfer of blown pack spoilage causing Clostridium spores from the farm to the meat plant is of growing concern to the meat industry. This study investigated the environmental niches of these Clostridium spp., specifically Clostridium estertheticum and Clostridium gasigenes in the beef and sheep farm environments in New Zealand. Faecal, soil, grass, drinking water, puddle water and feed (fodder beet, hay, bailage and silage, where available) samples were collected on five beef and sheep farms during Winter and Spring in 2018, in North and South Island, respectively. Beef and sheep farm samples were tested for C. estertheticum and C. gasigenes using enrichment plus PCR, qPCR and direct plating. C. estertheticum was detected in bovine faecal (4%), soil (2-18%) and grass (0-12%) samples at concentration of up to 2.0 log10 cfu/g. C. gasigenes were found in 18-46% of faecal, 16-82% of soil, 12-44% of grass, 0-44.4% of drinking water and 0-58.3% of puddle water samples tested and the direct counts ranged from 2.4 log10 cfu/ml in puddle water to 3.4 log10 cfu/g in soil. C. estertheticum were detected by qPCR in sheep farms in ovine feces (2.3%), soil (2.3%) and fodder beet (10%). All other sample types (grass, drinking water, puddle water, baleage, hay, silage and fodder beet) were negative using direct and enrichment plus PCR methods. In contrast C. gasigenes was detected in of faecal (22.7-38.6%), soil (22.7-84.1%), grass (17.5-34.1%) drinking water (35.7-78.6%), puddle water (33.3-40%), hay baleage (57%), silage (2%) and fodder beet (10%) at concentrations of up to 3.7 log10 cfu/g/ml. It was concluded that C. estertheticum and C. gasigenes were common on beef and sheep farms with the latter having higher incidence and mean concentration.

The prevalence of Clostridioides difficile on farms, in abattoirs and in retail foods in Ireland.

An increasing proportion of Clostridioides difficile infections (CDI) are community acquired. This study tested farm, abattoir and retail food samples for C. difficile, using peer reviewed culture and molecular methods. The contamination rate on beef, sheep and broiler farms ranged from 2/30 (7%) to 25/30 (83%) in faeces, soil and water samples, while concentrations ranged from 2.9 log10 cfu/ml to 8.4 log10 cfu/g. The prevalence and associated counts were much lower in abattoir samples. Although 26/60 were C. difficile positive by enrichment and PCR, only 6 samples yielded counts by direct plating (1.1 log10 cfu/cm2 to 5.1 log10 cfu/g). At retail, 9/240 samples were C. difficile positive, including corned beef (1), spinach leaves (2), iceberg lettuce, little gem lettuce, wild rocket, coleslaw, whole milk yogurt and cottage cheese (1 sample each), with counts of up to 6.8 log10 cfu/g. The tcdA, tcdB, cdtA, cdtB, tcdC and tcdR genes were detected in 41%, 99.2%, 33.6%, 32%, 46.7% and 31.1%, respectively, of the 122 C. difficile isolates obtained. It was concluded that although the prevalence of C. difficile decreased along the food chain, retail foods were still heavily contaminated. This pathogen may therefore be foodborne, perhaps necessitating dietary advice for potentially vulnerable patients.

The impact of key processing stages and flock variables on the prevalence and levels of Campylobacter on broiler carcasses.

This study examined the impact of key processing stages and flock variables on the prevalence of Campylobacter on broiler carcasses. Overall, the prevalence of Campylobacter was 62% in caeca, and 68%, 65% and 62% in neck skin samples collected after evisceration, final wash and carcass chilling, respectively. Campylobacter were found in 32% of caeca, and 52%, 40% and 32% of neck skin samples collected after evisceration, final wash and carcass chilling, respectively from first thin broiler batches. Final thin broiler batches were more frequently contaminated with prevalences of 83% found in caeca, 80% in neck skin samples collected after evisceration and 83% found in neck skin samples collected after both final wash and carcass chilling stages (p < 0.05). Thinning status had a significant effect on Campylobacter counts with significantly higher counts observed in samples from final thin batches (p < 0.05). Highest Campylobacter concentrations in neck skin samples were observed at the evisceration stage in both first and final thin samples, with counts ranging from 2.0 to 3.8 log10 CFU/g and 2.3 to 4.8 log10 CFU/g in first and final thin batches, respectively. All first thin samples had counts below the European Union (EU) Process Hygiene Criterion threshold level of 3 log10 CFU/g after chilling while 52% of final thin batches had counts above this limit.

Quantitative microbial human exposure model for faecal indicator bacteria and risk assessment of pathogenic Escherichia coli in surface runoff following application of dairy cattle slurry and co-digestate to grassland.

Animal waste contains high numbers of microorganisms and therefore can present a potential biological threat to human health. During episodic rainfall events resulting in runoff, microorganisms in the waste and soil may migrate into surface runoff, contaminating surface water resources. A probabilistic human exposure (HE) model was created to determine exposure to faecal indicator bacteria (FIB): total coliforms (TC), E. coli and enterococci following application of bio-based fertiliser (dairy cattle slurry, digestate) to grassland; using a combination of experimental field results and literature-based data. This step was followed by a quantitative microbial risk assessment (QMRA) model for pathogenic E. coli based on a literature-based dose-response model. The results showed that the maximum daily HE (HEdaily) is associated with E. coli for unprocessed slurry (treatment T1) on day 1, the worst-case scenario where the simulated mean HEdaily was calculated as 2.84 CFU day -1. The results indicate that the overall annual probability of risk (Pannual) of illness from E. coli is very low or low based on the WHO safe-limit of Pannual as 10 -6. In the worst-case scenario, a moderate risk was estimated with simulated mean Pannual as 1.0 × 10 -5. Unpasteurised digestate application showed low risk on day 1 and 2 (1.651 × 10 -6, 1.167 × 10 -6, respectively). Pasteurised digestate showed very low risk in all scenarios. These results support the restriction imposed on applying bio-based fertiliser if there is any rain forecast within 48 h from the application time. This study proposes a future extension of the probabilistic model to include time, intensity, discharge, and distance-dependant dilution factor. The information generated from this model can help policymakers ensure the safety of surface water sources through the quality monitoring of FIB levels in bio-based fertiliser.

Individual and herd-level milk ELISA test status for Johne's disease in Ireland after correcting for non-disease-associated variables.

Antibody-detecting tests for Mycobacterium avium ssp. paratuberculosis (MAP) have low sensitivity and imperfect specificity for detection of infection. Sensitivity increases as the disease progresses. Aside from infection status and stage of disease, several factors affect test performance. These factors have not yet been studied in dairy cows producing lower volumes of milk with higher solids concentration, such as those managed in low-input, pasture-based production systems. Furthermore, the effect of correcting for these associations on individual and herd test status is also unknown. The first objective of this study was to examine the relationship between MAP antibody response in milk and milk yield, somatic cell count (SCC), fat and protein contents, and stage of lactation in dairy cows enrolled in the national Johne's Disease Control Programme (JDCP) in Ireland. The second objective was to examine the effect of correcting the antibody response for these associations on the test status of individual cows and herds, given that individual tests are often used to define a herd's status. Data were extracted for herds in the JDCP from January 2014 to December 2015 inclusive, consisting of 42,657 milk recordings from 18,569 cows across 187 dairy herds. Two linear regression models were constructed to investigate the association between log-transformed MAP sample-to-positive ratio and milk recording data and in primi- and multiparous cows. Days in milk was modeled as a B-spline in each model, and cow and herd were included as random effects. Across both models, natural log-transformed MAP antibody response was negatively associated with milk yield, positively associated with protein and fat production, and had a curvilinear association with log-transformed SCC. The association between MAP antibody response and days in milk varied over the course of the lactation. However, when combined, these variables explained only 5.1% of the variation in the antibody response of the population. After correcting for these associations, 93 multiparous cows and 20 primiparous cows changed category (negative, suspect, or positive). When considered at the herd-test level, out of a total of 531 herd tests, 1 herd changed from negative to positive, and 5 herds changed from positive to negative. This study provides useful information to aid in the interpretation of antibody results for herds testing animals for the presence of MAP infection. At an overall population level, correction of the serological response for non-disease-associated factors has the potential to change the status of only a small number of cows. At the herd level, the proportion of herds changing status was minimal. However, depending on the implications of a herd-level serological diagnosis, consideration should be given to correcting for these non-disease-associated variables within the context of national JD control programs.

Strategies and novel technologies to control Campylobacter in the poultry chain: A review.

Campylobacteriosis is one of the most common bacterial infections worldwide causing economic costs. The high prevalence of Campylobacter spp. in poultry meat is a result of several contamination and cross-contamination sources through the production chain. Moreover, survival mechanisms, such as biofilm formation, viable but nonculturable state, and antimicrobial resistance, enable its persistence during food processing. Therefore, mitigation strategies are necessary in order to avoid and/or inactivate Campylobacter at farm, abattoir, industry, and retail level. In this review, a number of potential strategies and novel technologies that could reduce the prevalence of Campylobacter in poultry meat have been identified and evaluated to provide a useful overview. At farm level for instance, biosecurity, bacteriocins, probiotics, feed and water additives, bacteriophages, and vaccination could potentially reduce colonization in chicken flocks. However, current technologies used in the chicken slaughter and processing industry may be less effective against this foodborne pathogen. Novel technologies and strategies such as cold plasma, ultraviolet light, high-intensity light pulses, pulsed electric fields, antimicrobials, and modified atmosphere packaging are discussed in this review for reducing Campylobacter contamination. Although these measures have achieved promising results, most have not been integrated within processing operations due to a lack of knowledge or an unwillingness to implement these into existing processing systems. Furthermore, a combination of existing and novel strategies might be required to decrease the prevalence of this pathogen in poultry meat and enhance food safety. Therefore, further research will be essential to assess the effectiveness of all these strategies.

Diversity and composition of the gut microbiota of Atlantic salmon (Salmo salar) farmed in Irish waters.

AIMS: Information on the gut microbiota of salmon is essential for optimizing nutrition while maintaining host health and welfare. This study's objectives were to characterize the microbiota in the GI tract of Atlantic salmon (Salmo salar) farmed in waters off the west coast of Ireland and to investigate whether there is a difference in microbiota diversity between the proximal and distal regions of the intestine. METHODS AND RESULTS: The microbiota from the proximal and distal intestine (PI and DI, respectively) of Atlantic salmon was examined using MiSeq Illumina high-throughput sequencing of the 16S ribosomal RNA gene. The PI region had greater bacterial diversity than the DI region. Six phyla were present in the DI samples, dominated by Tenericutes and Firmicutes. These six phyla were also amongst the 12 phyla detected in the PI samples. The PI microbiota was dominated by Tenericutes, Firmicutes, Bacteroidetes and Proteobacteria. A core microbiota of 20 operational taxonomic units (OTUs) common to both regions was observed. CONCLUSIONS: It was concluded that Tenericutes were the dominant phylum in both PI and DI samples, and the PI region had greater Shannon and Simpson diversity of bacteria. However, further work is required to identify the functionality of the salmon microbiota. SIGNIFICANCE AND IMPACT OF THE STUDY: Our study determined the composition and diversity of the intestinal microbiota in adult salmon from a commercial fishery and provides data to improve our understanding of their contributions to the nutrition, health and welfare of Atlantic salmon farmed in Irish waters.

Spoilage indicator bacteria in farmed Atlantic salmon (Salmo salar) stored on ice for 10 days.

This study investigated the growth of indicator and spoilage bacteria on whole Atlantic salmon (Salmo salar) stored aerobically at 2 °C. On days 0, 2, 3, 6, 8 and 10 microbiological analysis was carried out on inner flesh and outer skin samples as well as outer skin swabs (25 cm2 surface areas). Mesophilic total viable counts (TVCm) on skin, flesh and swab samples increased from 1.9, 1.1 and 2.7 log10 CFUcm2 to 6.0, 5.1 and 5.7 log10 CFU/cm2 after 10 days, respectively. Psychrotrophic counts (TVCp), increased from 2.2, 1.8 and 3.1 log10 CFU/cm2 to 6.2, 5.3 and 5.9 log10 CFU/cm2, for skin, flesh and swab samples respectively. Hydrogen sulphide producing bacteria (HSPB), lactic acid bacteria (LAB), Pseudomonas spp., Brochothrix thermosphacta and Photobacterium spp. grew well with similar growth rates (mean generation times of 17.2-26 h). It was concluded that the shelf-life of salmon at 2 °C was approximately 10 days and that HSPB, LAB, Pseudomonas spp., Br. thermosphacta and Photobacterium spp. may be a better indicator of fish spoilage rather than TVC growth, with a count of 5-6 log10 CFU/cm2 indicating the end of shelf-life.

An investigation of vtx2 bacteriophage transduction to different Escherichia coli patho-groups in food matrices and nutrient broth.

This study investigated bacteriophage (phage) mediated transfer of the vtx2 gene from a donor Escherichia coli (C600φ3538(Δvtx2::cat)) to enteropathogenic (EPEC), enterotoxigenic (ETEC), enteroaggregative (EAEC), enteroinvasive (EIEC) and diffusely adherent (DAEC) E. coli strains in LB broth, milk, ground beef and lettuce. Two bacterial concentrations for both the E. coli donor and recipient strains, 3 and 5 log10 CFU/ml (LB broth and milk)/g (beef) or/cm2 (lettuce), were used. When transductants were obtained, the location of insertion of the phage (insertion sites wrbA, yehA, sbcB, yecE and/or Z2577) in the E. coli chromosome was investigated by PCR. The vtx2 gene was readily transferred to EAEC O104:H4 (E99518) in all matrices and inserted into the chromosome at the sbcB locus. At higher cell concentrations, transductants were also obtained with ETEC E4683, ETEC E8057 (insertion site unknown) and DAEC O75:H- E66438 (insertion site unknown) in LB broth and milk. It was concluded that the vtx2 gene may be transferred by bacteriophage to different E. coli pathotypes in laboratory and food matrices, resulting in the spread of the vtx2 gene and the emergence of novel foodborne pathogens.

Light based technologies for microbial inactivation of liquids, bead surfaces and powdered infant formula.

This study evaluates the potential of continuous wave Ultraviolet C light (UV-C) and broad-spectrum intense pulsed light (in this study referred to as High Intensity Light Pulses, HILP) for the inactivation of pathogens of public concern in powdered infant formula (PIF) producers. To achieve this goal a sequential set of experiments were performed, firstly in clear liquid media, secondly on the surface of spherical beads under agitation and, finally in PIF. L. innocua was the most sensitive microorganism to both technologies under all conditions studied with reductions exceeding 4 log10 cycles in PIF. In the clear liquid medium, the maximum tolerance to light was observed for C. sakazakii against UV-C light and for B. subtilis spores against HILP, with a fluence of approximately 17 mJ/cm2 required for a 1 log10 cycle inactivation (D value) of each species. In PIF it was possible to inactivate >99% of the vegetative cell populations by HILP with a fluence of 199 mJ/cm2 and of B. subtilis spores by doubling the fluence. By contrast, for UV-C treatments a fluence of 2853 mJ/cm2 was needed for 99.9% reduction of C. sakazakii, which was the most light-resistant microorganism to UV-C. Results here obtained clearly show the potential for light-based interventions to improve PIF microbiological safety.

The microbiology of beef carcasses and primals during chilling and commercial storage.

The primary objective of this study was to characterise (microbiology and physical parameters) beef carcasses and primals during chilled storage. A minor aim was to compare observed growth of key spoilage bacteria on carcasses with that predicted by ComBase and the Food Safety Spoilage Predictor (FSSP). Total viable count (TVC), total Enterobacteriacae count (TEC), Pseudomonas spp., lactic acid bacteria (LAB), Brochothrix thermosphacta and Clostridium spp. were monitored on beef carcasses (n = 30) and primals (n = 105) during chilled storage using EC Decision 2001/471/EC and ISO sampling/laboratory procedures. The surface and/or core temperature, pH and water activity (aw) were also recorded. Clostridium (1.89 log10 cfu/cm2) and Pseudomonas spp. (2.12 log10 cfu/cm2) were initially the most prevalent bacteria on carcasses and primals, respectively. The shortest mean generation time (G) was observed on carcasses with Br. thermosphacta (20.3 h) and on primals with LAB (G = 68.8 h) and Clostridium spp. (G = 67 h). Over the course of the experiment the surface temperature decreased from 37 °C to 0 °C, pH from 7.07 to 5.65 and aw from 0.97 to 0.93 The observed Pseudomonas spp. and Br. thermosphacta growth was more or less within the range of predictions of Combase. In contrast, the FSSP completely overestimated the growth of LAB. This study contributes to the very limited microbiological data on beef carcasses and primals during chilling.

Relative importance of herd-level risk factors for probability of infection with paratuberculosis in Irish dairy herds.

Control of paratuberculosis is challenging due to the relatively poor performance of diagnostic tests, a prolonged incubation period, and protracted environmental survival. Prioritization of herd-level interventions is not possible because putative risk factors are often not supported by risk factor studies. The objective for this study was to investigate the relative importance of risk factors for an increased probability of herd paratuberculosis infection. Risk assessment data, comprehensive animal purchase history, and diagnostic test data were available for 936 Irish dairy herds. Both logistic regression and a Bayesian ß regression on the outcome of a latent class analysis were conducted. Population attributable fractions and proportional reduction in variance explained were calculated for each variable in the logistic and Bayesian models, respectively. Routine use of the calving area for sick or lame cows was found to be a significant explanatory covariate in both models. Purchasing behavior for the previous 10 yr was not found to be significant. For the logistic model, length of time calves spend in the calving pen (25%) and routine use of the calving pen for sick or lame animals (14%) had the highest attributable fractions. For the Bayesian model, the overall R2 was 16%. Dry cow cleanliness (7%) and routine use of the calving area for sick or lame cows (6%) and had the highest proportional reduction in variance explained. These findings provide support for several management practices commonly recommended as part of paratuberculosis control programs; however, a large proportion of the observed variation in probability of infection remained unexplained, suggesting other important risks factors may exist.