Lifestyle of Listeria monocytogenes and food safety: Emerging listericidal technologies in the food industry.

Listeria monocytogenes, a causative agent of listeriosis, is a major foodborne pathogen. Among pathogens, L. monocytogenes stands out for its unique ecological and physiological characteristics. This distinct lifestyle of L. monocytogenes has a significant impact on food safety and public health, mainly through the ability of this pathogen to multiply at refrigeration temperature and to persist in the food processing environment. Due to a combination of these characteristics and emerging trends in consumer preference for ready-to-eat and minimally processed food, there is a need to develop effective and sustainable approaches to control contamination of food products with L. monocytogenes. Implementation of an efficient and reliable control strategy for L. monocytogenes must first address the problem of cross-contamination. Besides the preventive control strategies, cross-contamination may be addressed with the introduction of emerging post packaging non-thermal or thermal hurdles that can ensure delivery of a listericidal step in a packed product without interfering with the organoleptic characteristics of a food product. This review aims to present the most relevant findings underlying the distinct lifestyle of L. monocytogenes and its impact on food safety. We also discuss emerging food decontamination technologies that can be used to better control L. monocytogenes.

Kiwifruit Skin and Flesh Contributions to Fecal Bulking and Bacterial Abundance in Rats.

Changes in fecal bulk and bacterial abundance due to separately consumed skin and flesh of four kiwifruit cultivars was determined using a rat model designed to estimate the fecal bulking potential of human foods. Dry matter contribution by skin to 100 g of fresh kiwifruit was less than 5% in all cultivars, whereas flesh dry matter contributed up to 20% of fresh fruit weight. Dietary fiber was 35-49% of skin compared with 8-23% of flesh on a dry weight basis. The skin significantly increased whole fruit fecal bulking, but the total bulk per 100 g kiwifruit was less than 10% of daily fecal bulk recommended for optimal gut health. Kiwifruit (skin or flesh) substantially increased the abundance of Lachnospiraceae and Lactobacillus spp. within the gut. Fermentation and prebiosis therefore probably play a greater role than fermentation-resistant dietary fiber in gut health benefits of kiwifruit.

Effects of Blackcurrant and Dietary Fibers on Large Intestinal Health Biomarkers in Rats.

This study examined the effects of anthocyanin-rich blackcurrant extract and dietary fibers individually and their combinations on biomarkers of large intestinal health in rats. After six weeks of feeding, rats fed diets with blackcurrant gained significantly less body weight and reduced their food intake resulting in a lower food efficiency compared with those rats fed control diets. Combining dietary fiber (apple or broccoli) with blackcurrant in the diet was more effective in reducing the body weight gain and food intake. Cecal bacterial populations and short-chain fatty acids differed between the experimental diets. Blackcurrants significantly altered the bacterial populations by increasing the abundance of Bacteroides-Prevotella-Porphyromonas group and Lactobacillus spp., while decreasing the abundance of Bifidobacterium spp. and Clostridium perfringens. Propionic acid concentrations were increased by the diets with blackcurrant. Butyric acid concentrations were increased by dietary fiber supplementation. Dietary fiber increased the number of goblet cells in the colon. Diets with blackcurrant were more effective in altering the biomarkers of large intestinal health than those without blackcurrant.

Influence of Dietary Avocado on Gut Health in Rats.

This study investigated the impact of diets containing various levels of avocado (5, 10 and 15%) on gut health in rats fed for six weeks. Avocado-fed rats had significantly higher food intakes while their body weights remained similar to the control diet-fed rats. No significant changes in intestinal bacterial populations (ileum, cecum and colon) were found in rats fed avocado diets compared to the control diet. Ileum and colon tissues of rats fed avocado diets showed significantly higher expression of genes (ß-defensin 1, mucin 3 or mucin 4) and a greater number of mucin-producing goblet cells in the colon. The percentage of avocado in the diet had varying effects in altering the biomarkers, whereby diet containing 15% avocado was the more effective diet. This study delivers new knowledge on the role of avocado on gut health in rats.

Dietary flavonoids from modified apple reduce inflammation markers and modulate gut microbiota in mice.

Apples are rich in polyphenols, which provide antioxidant properties, mediation of cellular processes such as inflammation, and modulation of gut microbiota. In this study we compared genetically engineered apples with increased flavonoids [myeloblastis transcription factor 10 (MYB10)] with nontransformed apples from the same genotype, "Royal Gala" (RG), and a control diet with no apple. Compared with the RG diet, the MYB10 diet contained elevated concentrations of the flavonoid subclasses anthocyanins, flavanol monomers (epicatechin) and oligomers (procyanidin B2), and flavonols (quercetin glycosides), but other plant secondary metabolites were largely unaltered. We used these apples to investigate the effects of dietary flavonoids on inflammation and gut microbiota in 2 mouse feeding trials. In trial 1, male mice were fed a control diet or diets supplemented with 20% MYB10 apple flesh and peel (MYB-FP) or RG apple flesh and peel (RG-FP) for 7 d. In trial 2, male mice were fed MYB-FP or RG-FP diets or diets supplemented with 20% MYB10 apple flesh or RG apple flesh for 7 or 21 d. In trial 1, the transcription levels of inflammation-linked genes in mice showed decreases of >2-fold for interleukin-2 receptor (Il2rb), chemokine receptor 2 (Ccr2), chemokine ligand 10 (Cxcl10), and chemokine receptor 10 (Ccr10) at 7 d for the MYB-FP diet compared with the RG-FP diet (P < 0.05). In trial 2, the inflammation marker prostaglandin E(2) (PGE(2)) in the plasma of mice fed the MYB-FP diet at 21 d was reduced by 10-fold (P < 0.01) compared with the RG-FP diet. In colonic microbiota, the number of total bacteria for mice fed the MYB-FP diet was 6% higher than for mice fed the control diet at 21 d (P = 0.01). In summary, high-flavonoid apple was associated with decreases in some inflammation markers and changes in gut microbiota when fed to healthy mice.

Apple polyphenol extracts protect against aspirin-induced gastric mucosal damage in rats.

The protective role of two apple polyphenol extracts, Douglas-FB (FB) and Douglas-EF (EF), on gastric mucosal damage following aspirin ingestion was investigated in healthy rats. Polyphenol content of the apple extracts varied, with the EF extract having 20% w/w polyphenols and a high proportion of flavanols as epicatechin and procyanidin, whereas the FB extract comprised 12% w/w polyphenols, which were mostly flavonols as quercetin glycosides. Male Sprague-Dawley rats were allocated to control, FB and EF groups and fed the experimental diet during the 10-day trial. Control treatment rats received 1 mL of deionised water, whereas apple polyphenol treatment group rats, FB and EF received a concentration of 10(-2) m polyphenols in 1 mL deionised water daily via oral gavage. At the end of 10-day feeding period, rats were fasted overnight, and the following morning, aspirin (200 mg/kg) was given by oral gavage. Four hours after aspirin administration, the animals were euthanised, and samples taken for analysis. Both apple polyphenol extracts significantly reduced the ulcer area, ulcer lesion index and gastric injury score. The glutathione in gastric mucosa was increased significantly in rats given FB apple extract. Despite their different polyphenol compositions, FB and EF apple extracts assisted in protecting the gastric mucosa following acute aspirin administration in rats.

In vitro utilization of gold and green kiwifruit oligosaccharides by human gut microbial populations.

We examined the effects of whole kiwifruit on gut microbiota using an in vitro batch model of gastric-ileal digestion and colonic fermentation. Faecal fermentations of gold and green kiwifruit, inulin and water (control) digests were performed for up to 48 h. As compared to the control, gold and green kiwifruit increased Bifidobacterium spp. by 0.9 and 0.8 log(10) cfu/ml, respectively (P < 0.001), and the Bacteroides-Prevotella-Porphyromonas group by 0.4 and 0.5 log(10) cfu/ml, respectively. Inulin only had a bifidogenic effect (+0.4 log(10) cfu/ml). This was accompanied with increases in microbial glycosidases, especially those with substrate specificities relating to the breakdown of kiwifruit oligosaccharides, and with increased generation of short chain fatty acids. The microbial metabolic activity was sustained for up to 48 h, which we attribute to the complexity of the carbohydrate substrate provided by whole kiwifruit. Kiwifruit fermenta supernatant was also separately shown to affect the in vitro proliferation of Bifidobacterium longum, and its adhesion to Caco-2 intestinal epithelial cells. Collectively, these data suggest that whole kiwifruit may modulate human gut microbial composition and metabolism to produce metabolites conducive to increased bifidobacteria-host association.

Pectin Influences the Absorption and Metabolism of Polyphenols from Blackcurrant and Green Tea in Rats.

Consumption of polyphenols and dietary fiber as part of a normal diet is beneficial to human health. In this study, we examined whether different amounts of dietary soluble fiber (pectin) affect the absorption and metabolism of polyphenols from blackcurrant and green tea in rats. After 28 days, the rats fed blackcurrant and green tea with pectin (4 or 8%) had significantly lower body weight gain and food intake compared to the rats fed a control diet. Rats fed a blackcurrant and green tea diet with 8% pectin had significantly higher fecal nitrogen output and lower protein digestibility. No polyphenols were observed in the urine, feces and plasma of rats fed the control diet. Parent catechins and flavonols were absent in urine obtained from all diet groups. Gallocatechin glucuronide was only observed in the plasma of rats fed the blackcurrant and green tea diet without pectin. Meanwhile, epicatechin and catechin gallate were present in the feces of rats fed a blackcurrant and green tea diet with and without 4% pectin. Pectin (4 or 8%) added to the blackcurrant and green tea diet increased the plasma antioxidant capacity in rats. Inclusion of pectin in the diet altered the host absorption and metabolism of polyphenols from blackcurrant and green tea.

Goat and cow milk differ in altering microbiota composition and fermentation products in rats with gut dysbiosis induced by amoxicillin.

Antibiotics are effective treatments for bacterial infections, however, their oral administration can have unintended consequences and may alter the gut microbiota composition. In this study, we examined the influence of antibiotics on the induction of gut dysbiosis and then evaluated the potential of cow and goat milk to restore the microbiota composition and metabolism in newly weaned rats. In the first study (gut dysbiosis model), rats were treated with amoxicillin, a mixture of antibiotics (ampicillin, gentamicin and metronidazole) or no antibiotics (control). Antibiotics reduced the rat body weights, food intakes and faecal outputs compared to the control group. Gut length was significantly decreased after the antibiotic intake. The bacterial populations (Bifidobacterium spp., Lactobacillus spp. and total bacteria) and short-chain fatty acids (SCFAs; acetic, butyric and propionic) concentrations in rat caecum, colon and faeces were significantly altered by the antibiotic treatments. In the second study, we examined the effects of cow and goat milk in restoring bacterial populations and metabolism in rats with gut dysbiosis induced by amoxicillin. Goat milk significantly increased the numbers of Bifidobacterium spp. and Lactobacillus spp. and decreased the numbers of Clostridium perfringens in the caecum and colon of rats treated with amoxicillin. Whereas, rats fed cow milk had higher Lactobacillus spp. and lower C. perfringens in the gut. Caecal and colonic SCFAs (acetic, butyric and propionic) concentrations differed significantly between rats fed cow and goat milk diets. Overall, goat and cow milk varied in their effects on the immature gut following antibiotic-induced dysbiosis in a rat model.

Influence of farming methods and seawater depth on Vibrio species in New Zealand Pacific oysters.

Studies conducted in seawaters around New Zealand have shown the numbers of human pathogenic Vibrio spp. are usually low, but high numbers sometimes occur during warmer summer/autumn months (January - April). In this study, Pacific oysters (Crassostrea gigas) were grown at Kaipara Harbour and Mahurangi Harbour in New Zealand at different heights from the seafloor in different ways: fixed positons intertidally and subtidally, and as floating long lines over the 2013 and 2014 summer periods. Two geographically distinct commercial harvest areas: Coromandel Harbour (North Island) and Croisilles Harbour (South Island) in New Zealand were also compared in 2015 where oysters are grown under different methods. Detection and enumeration of Vibrio spp. was performed according to the Bacteriological Analytical Manual using the Most Probable Number approach and real-time polymerase chain reaction technique. The only significant growing method effect was observed in Mahurangi Harbour, where intertidal oysters at 1.5 m from the seafloor had higher numbers of trh + Vibrio parahaemolyticus than other intertidal samples from Kaipara Harbour and Coromandel Harbour. All other samples showed a relationship with surface seawater temperature, but not with distance from seafloor or farming method. Overall, there is no clear evidence that different oyster farming methods (floating, subtidal or intertidal at different depths) affect Vibrio spp. population sizes, which were dominated by seasonal changes and environmental parameters.

Microbiota Composition of Breast Milk from Women of Different Ethnicity from the Manawatu-Wanganui Region of New Zealand.

Human breastmilk components, the microbiota and immune modulatory proteins have vital roles in infant gut and immune development. In a population of breastfeeding women (n = 78) of different ethnicities (Asian, Maori and Pacific Island, New Zealand European) and their infants living in the Manawatu-Wanganui region of New Zealand, we examined the microbiota and immune modulatory proteins in the breast milk, and the fecal microbiota of mothers and infants. Breast milk and fecal samples were collected over a one-week period during the six to eight weeks postpartum. Breast milk microbiota differed between the ethnic groups. However, these differences had no influence on the infant's gut microbiota composition. Based on the body mass index (BMI) classifications, the mother's breast milk and fecal microbiota compositions were similar between normal, overweight and obese individuals, and their infant's fecal microbiota composition also did not differ. The relative abundance of bacteria belonging to the Bacteroidetes phylum was higher in feces of infants born through vaginal delivery. However, the bacterial abundance of this phylum in the mother's breast milk or feces was similar between women who delivered vaginally or by cesarean section. Several immune modulatory proteins including cytokines, growth factors, and immunoglobulin differed between the BMI and ethnicity groups. Transforming growth factor beta 1 and 2 (TGFß1, TGFß2) were present in higher concentrations in the milk from overweight mothers compared to those of normal weight. The TGFß1 and soluble cluster of differentiation 14 (sCD14) concentrations were significantly higher in the breast milk from Maori and Pacific Island women compared with women from Asian and NZ European ethnicities. This study explores the relationship between ethnicity, body mass index, mode of baby delivery and the microbiota of infants and their mothers and their potential impact on infant health.

Composition and safety evaluation of tea from New Zealand kawakawa (Piper excelsum).

Kawakawa (Piper excelsum) has food, medicinal and cultural importance to the indigenous Maori people of New Zealand, and is being incorporated into a range of commercial food and therapeutic products, including tea. In this study, the chemical compositions of kawakawa fresh leaves, dried leaves for tea, and hot brewed tea, were analysed and compared. The key metabolites were diayangambin, elemicin, myristicin, unidentified lignans and amides. The safety of brewed tea and tea leaves were evaluated in 8 week old Sprague Dawley rats in a 14 day acute study followed by a 28 day subacute study. In the 14 day study, the rats received the equivalent of 1, 2, 3 or 4 cups of kawakawa tea, and the rats in the 28 day study received daily doses that were equivalent to 4 cups per day. There were no adverse effects observed in the rats, and body weights and food intakes were not significantly different between the control and the kawakawa treated animals. There were small differences in organ weights, biochemical and haematology parameters observed in the rats given the kawakawa tea. In conclusion, the consumption of kawakawa tea could be considered safe within the conditions used in this study.

Effect of probiotic strains Lactobacillus acidophilus LAFTI L10 and Lactobacillus paracasei LAFTI L26 on systemic immune functions and bacterial translocation in mice.

The immunostimulatory effects of Lactobacillus acidophilus LAFTI L10 and Lactobacillus paracasei LAFTI L26 were evaluated to determine their probiotic properties for functional food applications. Mice were given oral doses of either L. acidophilus L10 or L. paracasei L26 (108 CFU/50 microl/day), and the effects on immune responses and bacterial translocation were assessed after the 14-day feeding trial. The proliferative responses of splenocytes to concanavalin A and lipopolysaccharide were significantly higher in mice fed L. acidophilus. Concanavalin A-induced splenocyte proliferative responses increased significantly in mice fed L. paracasei. Interleukin 10 and interferon gamma production from the splenocytes stimulated with concanavalin A were enhanced in mice fed L. acidophilus or L. paracasei. The phagocytic activity of the peritoneal macrophages was significantly higher in mice fed either L. acidophilus or L. paracasei compared with control mice. In mice fed L. acidophilus or L. paracasei, the bacterial translocation of Lactobacillus spp. and total anaerobes to Peyer's patches and mesenteric lymph nodes was modulated compared with that in the control mice. Furthermore, there was no indication of disruption of intestinal mucosal integrity and thus no bacterial translocation to spleen, liver, or blood in mice fed either L. acidophilus or L. paracasei. The results of this study indicate that L. acidophilus and L. paracasei are potential enhancers of systemic immunity and are nonpathogenic, as suggested by their bacterial translocation profiles in healthy mice.

Human Milk Composition and Dietary Intakes of Breastfeeding Women of Different Ethnicity from the Manawatu-Wanganui Region of New Zealand.

Human milk is nutrient rich, complex in its composition, and is key to a baby's health through its role in nutrition, gastrointestinal tract and immune development. Seventy-eight mothers (19⁻42 years of age) of Asian, Maori, Pacific Island, or of European ethnicity living in Manawatu-Wanganui, New Zealand (NZ) completed the study. The women provided three breast milk samples over a one-week period (6⁻8 weeks postpartum), completed a three-day food diary and provided information regarding their pregnancy and lactation experiences. The breast milk samples were analyzed for protein, fat, fatty acid profile, ash, selected minerals (calcium, magnesium, selenium, zinc), and carbohydrates. Breast milk nutrient profiles showed no significant differences between the mothers of different ethnicities in their macronutrient (protein, fat, carbohydrate, and moisture) content. The breast milk of Asian mothers contained significantly higher levels of polyunsaturated fatty acids (PUFAs), omega-3 (n-3) and omega-6 (n-6) fatty acids, docosahexaenoic acid (DHA), and linoleic acids. Arachidonic acid was significantly lower in the breast milk of Maori and Pacific Island women. Dietary intakes of protein, total energy, saturated and polyunsaturated fat, calcium, phosphorus, zinc, iodine, vitamin A equivalents, and folate differed between the ethnic groups, as well as the number of serves of dairy foods, chicken, and legumes. No strong correlations between dietary nutrients and breast milk components were found.

Immune enhancing effects of Lactobacillus acidophilus LAFTI L10 and Lactobacillus paracasei LAFTI L26 in mice.

The immune enhancing properties of Lactobacillus acidophilus LAFTI L10 and Lactobacillus paracasei LAFTI L26 in mice were investigated. Each mouse (BALB/c) was orally fed with cultures of either L. acidophilus or L. paracasei at 10(8) CFU/50 mul per day for 14 days. The effect of these strains on immunoglobulin A, interleukin-10 and interferon gamma producing cells in the gut immune system was determined by immunofluorescence assays. Systemic immune responses were analysed in mice serum upon euthanising after a 14-day feeding trial to estimate cytokines such as IL-10 and IFN-gamma by enzyme-linked immunosorbent assays. L. acidophilus and L. paracasei strains demonstrated an increase in the number of IgA producing cells, IL-10 and IFN-gamma cytokine producing cells in the small intestine. In the systemic immune response, mice fed with L. acidophilus or L. paracasei also enhanced the secretion of anti-inflammatory cytokine (IL-10) and pro-inflammatory cytokine (IFN-gamma). The results of this study suggest that L. acidophilus and L. paracasei were able to enhance specific gut and systemic immune responses in mice.

The fate of (13)C-labelled and non-labelled inulin predisposed to large bowel fermentation in rats.

The fate of stable-isotope (13)C labelled and non-labelled inulin catabolism by the gut microbiota was assessed in a healthy rat model. Sprague-Dawley male rats were randomly assigned to diets containing either cellulose or inulin, and were fed these diets for 3 days. On day (d) 4, rats allocated to the inulin diet received (13)C-labelled inulin. The rats were then fed the respective non-labelled diets (cellulose or inulin) until sampling (d4, d5, d6, d7, d10 and d11). Post feeding of (13)C-labelled substrate, breath analysis showed that (13)C-inulin cleared from the host within a period of 36 hours. Faecal (13)C demonstrated the clearance of inulin from gut with a (13)C excess reaching maximum at 24 hours (d5) and then declining gradually. There were greater variations in caecal organic acid concentrations from d4 to d6, with higher concentrations of acetic, butyric and propionic acids observed in the rats fed inulin compared to those fed cellulose. Inulin influenced caecal microbial glycosidase activity, increased colon crypt depth, and decreased the faecal output and polysaccharide content compared to the cellulose diet. In summary, the presence of inulin in the diet positively influenced large bowel microbial fermentation.

Kiwifruit-derived supplements increase stool frequency in healthy adults: a randomized, double-blind, placebo-controlled study.

The worldwide growth in the incidence of gastrointestinal disorders has created an immediate need to identify safe and effective interventions. In this randomized, double-blind, placebo-controlled study, we examined the effects of Actazin and Gold, kiwifruit-derived nutritional ingredients, on stool frequency, stool form, and gastrointestinal comfort in healthy and functionally constipated (Rome III criteria for C3 functional constipation) individuals. Using a crossover design, all participants consumed all 4 dietary interventions (Placebo, Actazin low dose [Actazin-L] [600 mg/day], Actazin high dose [Actazin-H] [2400 mg/day], and Gold [2400 mg/day]). Each intervention was taken for 28 days followed by a 14-day washout period between interventions. Participants recorded their daily bowel movements and well-being parameters in daily questionnaires. In the healthy cohort (n = 19), the Actazin-H (P = .014) and Gold (P = .009) interventions significantly increased the mean daily bowel movements compared with the washout. No significant differences were observed in stool form as determined by use of the Bristol stool scale. In a subgroup analysis of responders in the healthy cohort, Actazin-L (P = .005), Actazin-H (P < .001), and Gold (P = .001) consumption significantly increased the number of daily bowel movements by greater than 1 bowel movement per week. In the functionally constipated cohort (n = 9), there were no significant differences between interventions for bowel movements and the Bristol stool scale values or in the subsequent subgroup analysis of responders. This study demonstrated that Actazin and Gold produced clinically meaningful increases in bowel movements in healthy individuals.

Influence of green and gold kiwifruit on indices of large bowel function in healthy rats.

The effects of kiwifruit on large bowel health were investigated in healthy rats. Four-week old Sprague-Dawley rats were given diets containing 10% homogenized green kiwifruit, gold kiwifruit or 10% glucose solution (control) over 4 or 6 wk. Green kiwifruit increased the fecal output compared to control. Growth of certain bacterial species in cecum was influenced by both green and gold kiwifruit. A significant increase in cecal Lachnospiraceae in rats fed the green kiwifruit diet was observed at week 4. At week 6, green and gold kiwifruit diets assisted in improving colonic barrier function by upregulating the expression of mucin (MUC)-2, MUC3, Toll-like receptor (TLR)-4 or trefoil factor-3 genes. Gold kiwifruit consumption increased the colonic goblet cells per crypt at week 6. Significant negative correlations between E. coli and ß-defensin 1 and TLR4 expression were observed. Consuming green and gold kiwifruit for 6 wk significantly altered the biomarkers of large bowel health; indicating that regularly consuming kiwifruit helps attain optimal digestive health.

Modification of the colonic microbiota.

It is becoming clear that the ecology and functionality of the human gut microbiota are extremely diverse and complex. The microbiota have coevolved with us metabolically to live symbiotically and to share the workload of extracting nutrients and energy from the diet. It is also clear that a diet rich in fruit, vegetables, and whole grain cereals is good for general health and gut health and that this is due partly to the phytochemicals and partly to the nondigestible carbohydrates (or dietary fiber) that are present in plants. Kiwifruit contain polyphenolics and nondigestible carbohydrates in the form of pectic, hemicellulosic, and cellulosic polysaccharides, all of which can be degraded by various members of the gut microbiota and result in beneficial effects. This chapter summarizes how kiwifruit act to modify the colonic microbiota and the resultant beneficial effects on human health.