Efficacy of high-intensity pulsed light for the microbiological decontamination of chicken, associated packaging, and contact surfaces

Nonthermal Sterilization of Animal-based Foods by Intense Pulsed Light Treatment

The consumption of meat has been increasing, leading to a dynamic meat and meat processing industry. To maintain the quality and safety of meat products, various technologies have been explored, including intense pulsed light (IPL) technology. Several factors affect the inactivation of microorganisms by IPL treatment, including light intensity (fluence), treatment duration, pulse frequency, and the distance between the lamp and the samples. Meat products have been studied for IPL treatment, resulting in microbial reductions of approximately 0.4-2.4 Log. There are also impacts on color, sensory attributes, and physico-chemical quality, depending on treatment conditions. Processed meat products like sausages and ham have shown microbial reductions of around 0.1-4 Log with IPL treatment. IPL treatment has minimal impact on color and lipid oxidation in these products. Egg products and dairy items can also benefit from IPL treatment, achieving microbial reductions of around 1-7.8 Log. The effect on product quality varies depending on the treatment conditions. IPL technology has shown promise in enhancing the safety and quality of various food products, including meat, processed meat, egg products, and dairy items. However, the research results on animal-based food are not diverse and fragmentary, this study discusses the future research direction and industrial application through a review of these researches.

Pulsed Ultraviolet Light Decontamination of Meat Conveyor Surfaces

Contact with continuous belt conveyors during processing results in opportunities for pathogenic and spoilage microorganisms to contaminate meat products. The objective of this project is to investigate the germicidal response on the surface of food-grade conveyor belt materials treated with pulsed ultraviolet (PUV) light. Four conveyor belt types including: a stainless-steel chain-link belt, a polytetrafluoroethylene (PTFE)-coated fabric belt, a solid pliable polymer belt, and a rigid-linked polymer belt, were evaluated for the inactivation of Escherichia coli K12-NSR strain and lactic acid bacteria (LAB). Prior to bacterial inoculation, samples were classified as soiled or unsoiled, based on the presence or absence of pork intramuscular fluid on the surfaces of the conveyor samples. Using a variable speed conveyor, equipped with a Xenon flashlamp positioned 10-cm above the surface, each belt sample was exposed to PUV light at three fixed conveyor speeds: 3.05, 15.24, and 30.48 cm/sec, resulting in a total energy exposure of 3.31, 0.66 and 0.33 J/cm², respectively. For samples inoculated with E. coli K12-NSR, the surface condition (soiled or unsoiled) by treatment interaction was significant for microbial inactivation on the surface of the rigid polymer linked belt (P < 0.05). For samples inoculated with the LAB cocktail, the same interaction was significant for the PTFE-coated fabric belt and the solid pliable polymer belt (P < 0.05). Microbial reduction ranged from 0.74 to 5.04 log₁₀ CFU/cm² for E. coli K12-NSR and 0.63 to 4.61 Log₁₀ CFU/cm² for LAB for the evaluated treatment parameters. The results of this project demonstrate that PUV light is an effective means of decontamination for conveyor belts during food processing.

Pulsed Ultraviolet Light Treatment of Chicken Parts

With increasing production and consumption of chicken, it is appropriate to investigate the functionality and effectiveness of microbial reduction interventions and the qualitative effects they have on food. The effectiveness of pulsed ultraviolet (PUV) light applied to chicken on a moving conveyor was evaluated for inactivation of Escherichia coli on the surface of raw boneless/skinless (B/S) chicken breasts, B/S chicken thighs, and bone-in/skin-on chicken thighs. The conveyor height (distance from the flashlamp) and speed were set to deliver total energy fluences of 5, 10, 20, and 30 J/cm2 to the surface of the products. The product type by energy fluence interaction was significant (P = 0.015) for microbial reduction of E. coli. Exposure to PUV light for 5 and 30 J/cm2 resulted in Log10 reductions of 0.29 and 1.04 for B/S breasts, 0.34 and 0.94 for B/S thighs, and 0.10 and 0.62 for bone-in/skin-on thighs, respectively. Lipid oxidation and changes in color of chicken samples were evaluated after 30 J/cm2 of PUV light treatment. Lipid oxidation was measured at 0, 24, 48, and 120 h after the treatment. PUV light treatment did not produce significant (P &gt; 0.05) changes in lipid oxidation values for each product type. International Commission on Illumination L*, a*, and b* parameters were used to report lightness and color of samples before and after treatment for B/S breasts and thighs and bone-in/skin-on thighs. Color parameters were not significantly (P &gt; 0.05) affected by PUV light treatments. In conclusion, this study indicates that PUV light applied to the surface of raw chicken parts on a moving conveyor is an effective surface antimicrobial treatment while inducing minimal change in quality of the product over a 5-d storage period under aerobic conditions.

Review on Stress Tolerance in Campylobacter jejuni

Campylobacter spp. are the leading global cause of bacterial colon infections in humans. Enteropathogens are subjected to several stress conditions in the host colon, food complexes, and the environment. Species of the genus Campylobacter, in collective interactions with certain enteropathogens, can manage and survive such stress conditions. The stress-adaptation mechanisms of Campylobacter spp. diverge from other enteropathogenic bacteria, such as Escherichia coli, Salmonella enterica serovar Typhi, S. enterica ser. Paratyphi, S. enterica ser. Typhimurium, and species of the genera Klebsiella and Shigella. This review summarizes the different mechanisms of various stress-adaptive factors on the basis of species diversity in Campylobacter, including their response to various stress conditions that enhance their ability to survive on different types of food and in adverse environmental conditions. Understanding how these stress adaptation mechanisms in Campylobacter, and other enteric bacteria, are used to overcome various challenging environments facilitates the fight against resistance mechanisms in Campylobacter spp., and aids the development of novel therapeutics to control Campylobacter in both veterinary and human populations.

Edible Coating and Pulsed Light to Increase the Shelf Life of Food Products

The application of edible coatings (EC) in combination with pulsed light (PL) treatments represents an emerging approach for extending the shelf life of highly perishable but high value-added products, such as fresh-cut fruits and vegetables. The surface of these products would benefit from the protective effects of ECs and the PL decontamination capability. This review describes in detail the fundamentals of both EC and PL, focusing on the food engineering principles in the formulation and application of EC and the delivery of efficient PL treatments and the technological aspects related to the food characterization following these treatments and discussing the implementation of the two technologies, individually or in combination. The advantages of the combination of EC and PL are extensively discussed emphasizing the potential benefits that may be derived from their combination when preserving perishable foods. The downsides of combining EC and PL are also presented, with specific reference to the potential EC degradation when exposed to PL treatments and the screening effect of PL transmittance through the coating layer. Finally, the potential applications of the combined treatments to food products are highlighted, comparatively presenting the treatment conditions and the product shelf-life improvement.

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.

Decontamination of Chicken Thigh Meat by Pulsed Ultraviolet Light

Foodborne illness outbreaks associated with chicken can be reduced with effective decontamination interventions. The effectiveness of pulsed ultraviolet (PUV) light for destruction of Salmonella, E. coli, and Campylobacter on the surface of chicken thigh meat was investigated. Chicken thighs were inoculated to 6 to 7 log10 CFU/cm2 before exposure to PUV light for each of the above-mentioned pathogens. Treatment variables included the distance from the quartz window of the PUV light (8 and 13 cm) and treatment time (0, 5, 15, 30, and 45 s). Comparison of treated samples to control (0 s) samples allowed for quantification of microbial reduction due to PUV light treatment. Microbial reduction on lean surface chicken thighs (P < 0.05) with increasing duration of PUV light exposure for E. coli, Campylobacter, and Salmonella. Exposure to PUV light for 5 and 45 s on lean surface thighs resulted in log10 CFU/cm2 reductions of 1.22 and 2.02 for E. coli, 1.45 and 2.09 for Campylobacter, and 1.55 and 2.42 for Salmonella, respectively. Pulsed UV light exposure for 5 and 45 s on skin surface thighs resulted in log10 reductions of 1.19 and 1.96 for E. coli; 1.08 and 1.85 for Campylobacter, and 0.90 and 1.82 for Salmonella, respectively. Results indicate that PUV light is effective for reductions of bacterial populations on the surface of raw chicken meat.

Reviewing Interventions against Enterobacteriaceae in Broiler Processing: Using Old Techniques for Meeting the New Challenges of ESBL E. coli?

Extended-spectrum beta-lactamase- (ESBL-) producing Enterobacteriaceae are frequently detected in poultry and fresh chicken meat. Due to the high prevalence, an impact on human colonization and the spread of antibiotic resistance into the environment is assumed. ESBL-producing Enterobacteriaceae can be transmitted along the broiler production chain but also their persistence is reported because of insufficient cleaning and disinfection. Processing of broiler chickens leads to a reduction of microbiological counts on the carcasses. However, processing steps like scalding, defeathering, and evisceration are critical concerning fecal contamination and, therefore, cross-contamination with bacterial strains. Respective intervention measures along the slaughter processing line aim at reducing the microbiological load on broiler carcasses as well as preventing cross-contamination. Published data on the impact of possible intervention measures against ESBL-producing Enterobacteriaceae are missing and, therefore, we focused on processing measures concerning Enterobacteriaceae, in particular E. coli or coliform counts, during processing of broiler chickens to identify possible hints for effective strategies to reduce these resistant bacteria. In total, 73 publications were analyzed and data on the quantitative reductions were extracted. Most investigations concentrated on scalding, postdefeathering washes, and improvements in the chilling process and were already published in and before 2008 (n=42, 58%). Therefore, certain measures may be already installed in slaughterhouse facilities today. The effect on eliminating ESBL-producing Enterobacteriaceae is questionable as there are still positive chicken meat samples found. A huge number of studies dealt with different applications of chlorine substances which are not approved in the European Union and the reduction level did not exceed 3 log10 values. None of the measures was able to totally eradicate Enterobacteriaceae from the broiler carcasses indicating the need to develop intervention measures to prevent contamination with ESBL-producing Enterobacteriaceae and, therefore, the exposure of humans and the further release of antibiotic resistances into the environment.

High intensity light pulses to reduce microbial load in fresh cheese

The present study focused on the utilisation of High Intensity Light Pulses (HILP) treatment to preserve mozzarella cheese. First, the susceptibility of Pseudomonas fluorescens and Enterobacteriaceae to HILP (fluences from 0·39 to 28·0 J/cm2) in a transparent liquid was evaluated (in-vitro tests). Afterwards, the effects on inoculated mozzarella cheese were also assessed. Then untreated (Control) and HILP treated samples were packaged and stored at 10 °C for 2 weeks. Enterobacteriaceae, Pseudomonas spp. and pH were monitored during storage. In a transparent liquid (in-vitro tests) there was a significant microbial inactivation just with 2 s of treatment. On the inoculated cheese a relevant microbial reduction of about 1 log cycle was observed, according to the exposure to the treatments. For Pseudomonas spp. in particular, in the treated samples, the microbiological acceptability limit (106 cfu/g) was never reached after 2 weeks of refrigerated storage. To sum up, the efficacy of this treatment is very interesting because a microbial reduction was observed in treated samples. HILP treatment is able to control the microbial growth and may be considered a promising way to decontaminate the surface of mozzarella cheese.

Chicken fillets subjected to UV-C and pulsed UV light: Reduction of pathogenic and spoilage bacteria, and changes in sensory quality

We have compared the efficacy of continuous ultraviolet (UV-C) (254 nm) and pulsed UV light in reducing the viability of Salmonella Enteritidis, Listeria monocytogenes, Staphylococcus aureus, enterohemorrhagic Escherichia coli, Pseudomonas spp., Brochothrix thermospacta, Carnobacterium divergens, and extended-spectrum β-lactamase producing E. coli inoculated on chicken fillet surface. Fluences from 0.05 to 3.0 J/cm2 (10 mW/cm2, from 5 to 300 s) used for UV-C light resulted in average reductions from 1.1 to 2.8 log cfu/cm2. For pulsed UV light, fluences from 1.25 to 18.0 J/cm2 gave average reductions from 0.9 to 3.0 log cfu/cm2. A small change in the odor characterized as sunburnt and increased concentration of volatile compounds associated with burnt odor posed restrictions on the upper limit of UV treatment, however no sensory changes were observed after cooking the meat. Treatments under modified atmosphere conditions using a UV permeable top film gave similar or slightly lower bacterial reductions.

PRACTICAL APPLICATIONS

Ultraviolet (UV) light may be used for decontaminating the surface of food products and reduce viability of pathogenic and spoilage bacteria. Exposure of raw chicken fillet surface to various doses of continuous UV-C or pulsed UV light proposed in the present work represent alternatives for microbiological improvement of this product. Chicken fillets can be treated in intact packages covered with UV permeable top film, thus avoiding recontamination of the meat. UV-C light treatment is a low cost strategy with low maintenance, whereas pulsed UV light involves more elaborate equipment, but treatment times are short and less space is required. Both methods can be helpful for producers to manage the safety and quality of chicken fillets.

Recent findings in pulsed light disinfection

Nonthermal disinfection technologies are gaining increasing interest in the field of minimally processed food in order to improve the microbial safety or to extend the shelf life. Especially fresh-cut produce or meat and fish products are vulnerable to microbial spoilage, but, due to their sensitivity, they require gentle preservation measures. The application of intense light pulses of a broad spectral range comprising ultraviolet, visible and near infrared irradiation is currently investigated as a potentially suitable technology to reduce microbial loads on different food surfaces or in beverages. Considerable research has been performed within the last two decades, in which the impact of various process parameters or microbial responses as well as the suitability of pulsed light (PL) for food applications has been examined. This review summarizes the outcome of the latest studies dealing with the treatment of various foods including the impact of PL on food properties as well as recent findings about the microbicidal action and relevant process parameters.

Pulsed Light Treatment of Different Food Types with a Special Focus on Meat: A Critical Review

Today, the increasing demand for minimally processed foods that are at the same moment nutritious, organoleptically satisfactory, and free from microbial hazards challenges the research and development to establish alternative methods to reduce the level of bacterial contamination. As one of the recent emerging nonthermal methods, pulsed light (PL) constitutes a technology for the fast, mild, and residue-free surface decontamination of food and food contact materials in the processing environment. Via high frequency, high intensity pulses of broad-spectrum light rich in the UV fraction, viable cells as well as spores are inactivated in a nonselective multi-target process that rapidly overwhelms cell functions and subsequently leads to cell death. This review provides specific information on the technology of pulsed light and its suitability for unpackaged and packaged meat and meat products as well as food contact materials like production surfaces, cutting tools, and packaging materials. The advantages, limitations, risks, and essential process criteria to work efficiently are illustrated and discussed with relation to implementation on industrial level and future aspects. Other issues addressed by this paper are the need to take care of the associated parameters such as alteration of the product and utilized packaging material to satisfy consumers and other stakeholders.

Influence of Host Ecology and Behavior on Campylobacter jejuni Prevalence and Environmental Contamination Risk in a Synanthropic Wild Bird Species

Campylobacter jejuni is a foodborne pathogen that often leads to human infections through the consumption of contaminated poultry. Wild birds may play a role in the transmission of C. jejuni by acting as reservoir hosts. Despite ample evidence that wild birds harbor C. jejuni, few studies have addressed the role of host ecology in transmission to domestic animals or humans. We tested the hypothesis that host social behavior and habitat play a major role in driving transmission risk. C. jejuni infection and host ecology were studied simultaneously in wild American crows (Corvus brachyrhynchos) in Davis, CA, over 3 years. We found that 178 of 337 samples tested were culture positive (53%), with infection varying by season and host age. Among adult crows, infection rates were highest during the winter, when migrants return and crows form large communal roosts. Nestlings had the highest risk of infection, and whole-genome sequencing supports the observation of direct transmission between nestlings. We deployed global positioning system (GPS) receivers to quantify habitat use by crows; space use was nonrandom, with crows preferentially occupying some habitats while avoiding others. This behavior drastically amplified the risk of environmental contamination from feces in specific locations. This study demonstrates that social behavior contributes to infection within species and that habitat use leads to a heterogeneous risk of cross-species transmission.

IMPORTANCE

Campylobacter jejuni is the most common cause of gastroenteritis in industrialized countries. Despite efforts to reduce the colonization of poultry flocks and eventual infection of humans, the incidence of human C. jejuni infection has remained high. Because wild birds can harbor strains of C. jejuni that eventually infect humans, there has long been speculation that wild birds might act as an important reservoir in the C. jejuni infection cycle. We simultaneously studied infection prevalence, social behavior, and movement ecology in wild American crows (Corvus brachyrhynchos). We found that social behavior contributed to patterns of infection and that movement behavior resulted in some areas having a high risk of transmission while others had a low risk. The incorporation of ecological data into studies of C. jejuni in wild birds has the potential to resolve when and how wild birds contribute to domestic animal and human C. jejuni infection, leading to better control of initial poultry contamination.

Previous Homologous and Heterologous Stress Exposure Induces Tolerance Development to Pulsed Light in Listeria monocytogenes

As one of the emerging non-thermal technologies, pulsed light (PL) facilitates rapid, mild and residue-free microbial surface decontamination of food and food contact materials. While notable progress has been made in the characterization of the inactivation potential of PL, experimental data available on the tolerance development to the same (homologous) stress or to different (heterologous) stresses commonly applied in food manufacturing (e.g., acid, heat, salt) is rather controversial. The findings of the present study clearly indicate that both the homologous tolerance development against PL as well as the heterologous tolerance development from heat to PL can be triggered in Listeria monocytogenes. Further, conducted kinetic analysis confirmed that the conventionally applied log-linear model is not well suited to describe the inactivation of L. monocytogenes, when exposed to PL. Instead, the Weibull model as well as the log-linear + tail model were identified as suitable models. Transmission electron microscopic (TEM) approaches allow suggestions on the morphological alterations in L. monocytogenes cells after being subjected to PL.

Postharvest intervention technologies for safety enhancement of meat and meat based products; a critical review

Globally, the demand for safe, healthy and nutritious meat and allied products possesses improved taste with extended shelf life is mounting. Microbial safety is among the imperative challenges that prevails in meat products because they provide an ideal medium for the growth of microorganisms particularly pathogenic bacteria. The incidence of these microbes can result quality deterioration of products leading towards food borne diseases when consumed by peoples. Several preservation technologies like chemical and biological interventions are effective to retard or inactivate the growth of micro-organisms most commonly related to food-borne diseases. Despite these, innovative approaches like hydrostatic pressure processing, active packaging, pulse electric field, hurdle approach and use of natural antimicrobials can be deployed to enhance the safety of meat and meat products. The objective of review is to describe the current approaches and developing technologies for enhancing safety of meat and allied meat products.

Efficacy and mechanisms of murine norovirus inhibition by pulsed-light technology

Pulsed light is a nonthermal processing technology recognized by the FDA for killing microorganisms on food surfaces, with cumulative fluences up to 12 J cm(-2). In this study, we investigated its efficacy for inactivating murine norovirus 1 (MNV-1) as a human norovirus surrogate in phosphate-buffered saline, hard water, mineral water, turbid water, and sewage treatment effluent and on food contact surfaces, including high-density polyethylene, polyvinyl chloride, and stainless steel, free or in an alginate matrix. The pulsed-light device emitted a broadband spectrum (200 to 1,000 nm) at a fluence of 0.67 J cm(-2) per pulse, with 2% UV at 8 cm beneath the lamp. Reductions in viral infectivity exceeded 3 log10 in less than 3 s (5 pulses; 3.45 J cm(-2)) in clear suspensions and on clean surfaces, even in the presence of alginate, and in 6 s (11 pulses; 7.60 J cm(-2)) on fouled surfaces except for stainless steel (2.6 log10). The presence of protein or bentonite interfered with viral inactivation. Analysis of the morphology, the viral proteins, and the RNA integrity of treated MNV-1 allowed us to elucidate the mechanisms involved in the antiviral activity of pulsed light. Pulsed light appeared to disrupt MNV-1 structure and degrade viral protein and RNA. The results suggest that pulsed-light technology could provide an effective alternative means of inactivating noroviruses in wastewaters, in clear beverages, in drinking water, or on food-handling surfaces in the presence or absence of biofilms.

Efficacy of three light technologies for reducing microbial populations in liquid suspensions

The aim of the current study was to evaluate the effectiveness of three nonthermal light technologies (NUV-Vis, continuous UV, and HILP) on their ability to inactivate Escherichia coli K12 and Listeria innocua.  E. coli K12 was selected as a representative microorganism for the enterohaemorrhagic foodborne pathogen E. coli O157:H7 and L. innocua as a surrogate microorganism for the common foodborne pathogen Listeria monocytogenes, respectively. The liquid matrix used for the disinfection experiments was a liquid matrix (MRD solution). The results of the present study show that the HILP treatment inactivated both E. coli and L. innocua more rapidly and effectively than either continuous UV-C or NUV-vis treatment. With HILP at 2.5 cm from the lamp, E. coli and L. innocua populations were reduced by 3.07 and 3.77 log10 CFU/mL, respectively, after a 5 sec treatment time, and were shown to be below the limit of detection (<0.22 log10 CFU/mL) following 30 sec exposure to HILP (106.2 J/cm(2)). These studies demonstrate the bactericidal efficacy of alternative nonthermal light technologies and their potential as decontamination strategies in the food industry.

Modeling the inactivation of Salmonella Typhimurium, Listeria monocytogenes, and Salmonella Enteritidis on poultry products exposed to pulsed UV light

Pulsed UV light inactivation of Salmonella Typhimurium on unpackaged and vacuum-packaged chicken breast, Listeria monocytogenes on unpackaged and vacuum-packaged chicken frankfurters, and Salmonella Enteritidis on shell eggs was explained by log-linear and Weibull models using inactivation data from previous studies. This study demonstrated that the survival curves of Salmonella Typhimurium and L. monocytogenes were nonlinear exhibiting concavity. The Weibull model was more successful than the log-linear model in estimating the inactivations for all poultry products evaluated, except for Salmonella Enteritidis on shell eggs, for which the survival curve was sigmoidal rather than concave, and the use of the Weibull model resulted in slightly better fit than the log-linear model. The analyses for the goodness of fit and performance of the Weibull model produced root mean square errors of 0.059 to 0.824, percent root mean square errors of 3.105 to 21.182, determination coefficients of 0.747 to 0.989, slopes of 0.842 to 1.042, bias factor values of 0.505 to 1.309, and accuracy factor values of 1.263 to 6.874. Overall, this study suggests that the survival curves of pathogens on poultry products exposed to pulsed UV light are nonlinear and that the Weibull model may generally be a useful tool to describe the inactivation patterns for pathogenic microorganisms affiliated with poultry products.

Adaptation of Pseudomonas aeruginosa to a pulsed light-induced stress

AIMS

Pulsed light (PL) technology is an efficient surface decontamination process. Used in low transmitted energy conditions, PL induces a stress that can be perceived by bacteria. The effect of such a PL stress was investigated on the highly environmental adaptable germ Pseudomonas aeruginosa PAO1.

METHODS AND RESULTS

Pulses of transmitted energy (fluence) reaching 1·8Jcm(-2) can kill 10(9) bacteria. Application of a lower sublethal PL dose allowed the bacteria to resist and survive more efficiently to a subsequent dose of PL. This sublethal dose was not increasing the mutation frequency of Ps. aeruginosa, but altered the abundance of 15 proteins as revealed by a global proteome analysis, including stress-induced proteins, phage-related proteins, energy and carbon metabolisms, cell motility, and transcription and translation regulators.

CONCLUSIONS

A response to a low-energy PL dose takes place in Ps. aeruginosa, reducing the energy conversion systems, while increasing transcription and translation processes to produce proteins involved in chaperone mechanisms and phage-related proteins, probably to protect the bacterium against a new PL-induced stress.

SIGNIFICANCE AND IMPACT OF THE STUDY

Taken together, these results suggest that a low-energy PL dose is sufficient to provoke adaptation of Ps. aeruginosa, leading to enhancing its resistance to a subsequent lethal treatment.

Development of flexible antimicrobial packaging materials against Campylobacter jejuni by incorporation of gallic acid into zein-based films

In this study, antimicrobial films were developed against Campylobacter jejuni by incorporation of gallic acid (GA) into zein-based films. The zein and zein-wax composite films containing GA between 2.5 and 10 mg/cm(2) were effective on different C. jejuni strains in a concentration-dependent manner. Zein and zein-wax composite films showed different release profiles in distilled water but quite similar release profiles at solid agar medium. Depending on incorporated GA concentration, 60-80% of GA released from the films, while the remaining GA was bound or trapped by film matrix. The GA at 2.5 and 5 mg/cm(2) caused a considerable increase in elongation (57-280%) of all zein films and eliminated their classical flexibility problems. The zein-wax composite films were less flexible than zein films, but the films showed similar tensile strengths and Young's modulus. Scanning electron microscopy indicated different morphologies of zein and zein-wax composite films. This study clearly showed the good potential of zein and GA to develop flexible antimicrobial films against C. jejuni.

Following an imaginary Campylobacter population from farm to fork and beyond: a bacterial perspective

It has been known for decades that poultry meat is the most common single source for campylobacteriosis, yet the problem has not been solved. This review identifies some of the reasons why our attempts to reduce the incidence of this pathogen have largely failed. Based on the literature, the events a virtual population of Campylobacter may encounter, from growing in the gut of a broiler to eventually infecting humans and causing disease, are reviewed. Most steps in the farm-to-fork process are well studied, though there are gaps in our knowledge about survival and spread of Campylobacter populations before they enter the farm. Key events in the farm-to-fork chain that are suitable targets for prevention and control, to reduce food-borne campylobacteriosis, are indicated. Novel insights into the pathogenic mechanism responsible for disease in humans are summarized, which hypothesize that an overactive immune response is the reason for the typical inflammatory diarrhoea. A role of genetic microheterogeneity within a clonal population in this chain of events is being proposed here. The human host is not necessary for the survival of the bacterial species, nor have these bacteria specifically evolved to cause disease in that host. More likely, the species evolved for a commensal life in birds, and human disease can be considered as collateral damage owing to an unfortunate host-microbe interaction. The indirect environmental burden that results from poultry production should not be ignored as it may pose a diffuse, but possibly significant risk factor for disease.