The Impact of Wage Bargaining Regime on Firm-Level Competitiveness and Wage Inequality: The Case of Ireland. ESRI WP266. December 2008

This paper uses a linked employer-employee dataset to analyse the impact of institutional wage bargaining regimes on levels of average labour costs and within firm wage dispersion in private sector companies in Ireland. The results show that while centralised bargaining reduced labour costs within both the indigenous and foreign-owned sectors, the relative advantage was greater among foreign-owned firms. The analysis suggests that there are potentially large competitiveness gains to multinational companies that choose to locate in countries implementing a centralised bargaining system. Furthermore, the results provide additional support to the view that collective bargaining reduces within firm wage inequality

Characterisation of Listeria monocytogenes food-associated isolates to assess environmental fitness and virulence potential

The ability of Listeria monocytogenes isolates to survive within the food production environment (FPE), as well as virulence, varies greatly between strains. There are specific genetic determinants that have been identified which can strongly influence a strains ability to survive in the FPE and/or within human hosts. In this study, we assessed the FPE fitness and virulence potential, including efficacy of selected hygiene or treatment intervention, against 52 L. monocytogenes strains isolated from various food and food environment sources. Phenotypic tests were performed to determine the minimum inhibitory concentration of cadmium chloride and benzalkonium chloride and the sensitivities to five clinically relevant antibiotics. A genomic analysis was also performed to identify resistance genes correlating to the observed phenotypic resistance profiles, along with genetic determinants of interest which may elude to the FPE fitness and virulence potential. A transposon element containing a novel cadmium resistance gene, cadA7, a Tn916 variant insert in the hypervariable Listeria genomic island 1 region and an LGI2 variant were identified. Resistance to cadmium and disinfectants was prevalent among isolates in this study, although no resistance to clinically important antimicrobials was observed. Potential hypervirulent strains containing full length inlA, LIPI-1 and LIPI-3 were also identified in this study. Cumulatively, the results of this study show a vast array of FPE survival and pathogenicity potential among food production-associated isolates, which may be of concern for food processing operators and clinicians regarding L. monocytogenes strains colonising and persisting within the FPE, and subsequently contaminating food products then causing disease in at risk population groups

Changes of the bacterial community diversity on chicken carcasses through an Australian poultry processing line

Understanding the bacterial community profile through poultry processing could help the industry to produce better poultry products. In this study, 10 chicken carcasses were randomly sampled from before and after scalding, before and after immersion chilling, and after air chilling each through a modern commercial processing line, along with the contents of 10 caeca. The sampled processing line effectively reduced the bacterial counts by > 4.6 Log10 CFU/ml for each of Total Viable Counts, Escherichia coli and Campylobacter. However, the metagenomics results suggested that Lactobacillus, Staphylococcus and unclassified Lachnospiraceae persisted at all sampling stages. Pseudomonas, Paeniglutamicibacter, Chryseobacterium and Pseudarthrobacter comprised 47.2% in the bacterial community on samples after air chilling compared to 0.3% on samples after immersion chilling, whereas TVCs were the same. Overall, the current interventions of the investigated poultry processing line were unable to eliminate persistence of certain foodborne pathogens, despite a significant reduction of the overall bacterial counts. Chilling is an important controlling point in contamination/cross-contamination, particularly extended air chilling. Lastly, the large presence of Pseudomonas on chickens after air chilling may lead to downstream spoilage related issues, which needs more investigation to explore quantitatively the effect on the shelf life of poultry products

Novel Biocontrol Methods for Listeria monocytogenes Biofilms in Food Production Facilities

High mortality and hospitalization rates have seen Listeria monocytogenes as a foodborne pathogen of public health importance for many years and of particular concern for high-risk population groups. Food manufactures face an ongoing challenge in preventing the entry of L. monocytogenes into food production environments (FPEs) due to its ubiquitous nature. In addition to this, the capacity of L. monocytogenes strains to colonize FPEs can lead to repeated identification of L. monocytogenes in FPE surveillance. The contamination of food products requiring product recall presents large economic burden to industry and is further exacerbated by damage to the brand. Poor equipment design, facility layout, and worn or damaged equipment can result in Listeria hotspots and biofilms where traditional cleaning and disinfecting procedures may be inadequate. Novel biocontrol methods may offer FPEs effective means to help improve control of L. monocytogenes and decrease cross contamination of food. Bacteriophages have been used as a medical treatment for many years for their ability to infect and lyse specific bacteria. Endolysins, the hydrolytic enzymes of bacteriophages responsible for breaking the cell wall of Gram-positive bacteria, are being explored as a biocontrol method for food preservation and in nanotechnology and medical applications. Antibacterial proteins known as bacteriocins have been used as alternatives to antibiotics for biopreservation and food product shelf life extension. Essential oils are natural antimicrobials formed by plants and have been used as food additives and preservatives for many years and more recently as a method to prevent food spoilage by microorganisms. Competitive exclusion occurs naturally among bacteria in the environment. However, intentionally selecting and applying bacteria to effect competitive exclusion of food borne pathogens has potential as a biocontrol application. This review discusses these novel biocontrol methods and their use in food safety and prevention of spoilage, and examines their potential to control L. monocytogenes within biofilms in food production facilities

Effect of peracetic acid on Campylobacter in food matrices mimicking commercial poultry processing

Campylobacter persistence through poultry processing is an important food safety issue in many developed countries. This investigation aimed to determine the effectiveness of peracetic acid (PAA) in reducing Campylobacter during processing. Campylobacter jejuni was tested against PAA using laboratory-based food matrices under conditions that mimicked commercial poultry processing interventions, including scalding and chilling. The assessments utilised two Campylobacter poultry strains (2674 and 2704) with testing performed in three different food matrices (Buffered peptone water (BPW), chicken breast meat and meat-based broth) and under eight processing conditions. Campylobacter inactivation was measured across eight processing conditions which mimicked scalding (3.5 min, 54.5 °C and 57 °C) and chilling (30 min, 4 °C, with/without 80 ppm PAA), and combinations of scalding and chilling (with/without 80 ppm PAA). The organic matter in the meat-based broth protected Campylobacter against PAA, resulting in less Campylobacter inactivation compared to BPW and meat matrices. Processing conditions with PAA demonstrated a greater Campylobacter inactivation compared to those without PAA. Chilling with PAA, without prior scalding, led to a greater Campylobacter inactivation than any other processing conditions within BPW and with meat. This suggests a potential mechanism that heat exposure cross-protects Campylobacter allowing them to better survive subsequent PAA treatment. Importantly, strain 2674, known to be relatively resistant to chlorine, was more susceptible to PAA than strain 2704. This investigation suggests PAA to be an effective processing alternative applicable to secondary immersion chilling tanks when little or no organic matter accumulates and may be able to achieve greater Campylobacter inactivation. The study demonstrates PAA could be beneficial in controlling Campylobacter during poultry processing

Global Genome Response of <i>Escherichia coli</i> O157∶H7 Sakai during Dynamic Changes in Growth Kinetics Induced by an Abrupt Temperature Downshift

<div><p><i>Escherichia coli</i> O157∶H7 is a mesophilic food-borne pathogen. We investigated the growth kinetics of <i>E. coli</i> O157∶H7 Sakai during an abrupt temperature downshift from 35°C to either 20°C, 17°C, 14°C or 10°C; as well as the molecular mechanisms enabling growth after cold stress upon an abrupt downshift from 35°C to 14°C in an integrated transcriptomic and proteomic analysis. All downshifts caused a lag period of growth before growth resumed at a rate typical of the post-shift temperature. Lag and generation time increased with the magnitude of the shift or with the final temperature, while relative lag time displayed little variation across the test range. Analysis of time-dependent molecular changes revealed, in keeping with a decreased growth rate at lower temperature, repression of genes and proteins involved in DNA replication, protein synthesis and carbohydrate catabolism. Consistent with cold-induced remodelling of the bacterial cell envelope, alterations occurred in the expression of genes and proteins involved in transport and binding. The RpoS regulon exhibited sustained induction confirming its importance in adaptation and growth at 14°C. The RpoE regulon was transiently induced, indicating a potential role for this extracytoplasmic stress response system in the early phase of low temperature adaptation during lag phase. Interestingly, genes previously reported to be amongst the most highly up-regulated under oxidative stress were consistently down-regulated. This comprehensive analysis provides insight into the molecular mechanisms operating during adaptation of <i>E. coli</i> to growth at low temperature and is relevant to its physiological state during chilling in foods, such as carcasses.</p></div

Global Genome Response of <i>Escherichia coli</i> O157∶H7 Sakai during Dynamic Changes in Growth Kinetics Induced by an Abrupt Downshift in Water Activity

<div><p>The present study was undertaken to investigate growth kinetics and time-dependent change in global expression of <i>Escherichia coli</i> O157∶H7 Sakai upon an abrupt downshift in water activity (a_w). Based on viable count data, shifting <i>E. coli</i> from a_w 0.993 to a_w 0.985 or less caused an apparent loss, then recovery, of culturability. Exponential growth then resumed at a rate characteristic for the a_w imposed. To understand the responses of this pathogen to abrupt osmotic stress, we employed an integrated genomic and proteomic approach to characterize its cellular response during exposure to a rapid downshift but still within the growth range from a_w 0.993 to a_w 0.967. Of particular interest, genes and proteins with cell envelope-related functions were induced during the initial loss and subsequent recovery of culturability. This implies that cells undergo remodeling of their envelope composition, enabling them to adapt to osmotic stress. Growth at low a_w, however, involved up-regulating additional genes and proteins, which are involved in the biosynthesis of specific amino acids, and carbohydrate catabolism and energy generation. This suggests their important role in facilitating growth under such stress. Finally, we highlighted the ability of <i>E. coli</i> to activate multiple stress responses by transiently inducing the RpoE and RpoH regulons to control protein misfolding, while simultaneously activating the master stress regulator RpoS to mediate long-term adaptation to hyperosmolality. This investigation extends our understanding of the potential mechanisms used by pathogenic <i>E. coli</i> to adapt, survive and grow under osmotic stress, which could potentially be exploited to aid the selection and/or development of novel strategies to inactivate this pathogen.</p></div

Colonisation dynamics of Listeria monocytogenes strains isolated from food production environments

Listeria monocytogenes is a ubiquitous bacterium capable of colonising and persisting within food production environments (FPEs) for many years, even decades. This ability to colonise, survive and persist within the FPEs can result in food product cross-contamination, including vulnerable products such as ready to eat food items. Various environmental and genetic elements are purported to be involved, with the ability to form biofilms being an important factor. In this study we examined various mechanisms which can influence colonisation in FPEs. The ability of isolates (n = 52) to attach and grow in biofilm was assessed, distinguishing slower biofilm formers from isolates forming biofilm more rapidly. These isolates were further assessed to determine if growth rate, exopolymeric substance production and/or the agr signalling propeptide influenced these dynamics and could promote persistence in conditions reflective of FPE. Despite no strong association with the above factors to a rapid colonisation phenotype, the global transcriptome suggested transport, energy production and metabolism genes were widely upregulated during the initial colonisation stages under nutrient limited conditions. However, the upregulation of the metabolism systems varied between isolates supporting the idea that L. monocytogenes ability to colonise the FPEs is strain-specific

Gene expression fold changes resulting from microarray analysis and qRT-PCR for three selected genes.

a<p>Microarray results are expressed in fold change for ease of comparison.</p>b<p>NDE, not differentially expressed.</p

The growth response of exponential phase <i>E. coli</i> O157∶H7 Sakai upon an abrupt temperature downshift from 35°C to either 20°C, 17°C, 14°C or 10°C; as determined by optical density.

<p>The growth response of exponential phase <i>E. coli</i> O157∶H7 Sakai upon an abrupt temperature downshift from 35°C to either 20°C, 17°C, 14°C or 10°C; as determined by optical density.</p