Inhibitory Effect of Select Nitrocompounds and Chlorate against Yersinia ruckeri and Yersinia aleksiciae In Vitro

Yersinia ruckeri is an important fish pathogen causing enteric redmouth disease. Antibiotics have traditionally been used to control this pathogen, but concerns of antibiotic resistance have created a need for alternative interventions. Presently, chlorate and certain nitrocompounds were tested against Y. ruckeri as well as a related species within the genus, Y. aleksiciae, to assess the effects of these inhibitors. The results reveal that 9 mM chlorate had no inhibitory effect against Y. ruckeri, but inhibited growth rates and maximum optical densities of Y. aleksciciae by 20–25% from those of untreated controls (0.46 h−1 and 0.29 maximum optical density, respectively). The results further reveal that 2-nitropropanol and 2-nitroethanol (9 mM) eliminated the growth of both Y. ruckeri and Y. aleksiciae during anaerobic or aerobic culture. Nitroethane, ethyl nitroacetate and ethyl-2-nitropropionate (9 mM) were less inhibitory when tested similarly. Results from a mixed culture of Y. ruckeri with fish tank microbes and of Y. aleksiciae with porcine fecal microbes reveal that the anti-Yersinia activity of the tested nitrocompounds was bactericidal, with 2-nitropropanol and 2-nitroethanol being more potent than the other tested nitrocompounds. The anti-Yersinia activity observed with these tested compounds warrants further study to elucidate the mechanisms of action and strategies for their practical application.

Innovative Treatments Enhancing the Functionality of Gut Microbiota to Improve Quality and Microbiological Safety of Foods of Animal Origin

The gastrointestinal tract, or gut, microbiota is a microbial community containing a variety of microorganisms colonizing throughout the gut that plays a crucial role in animal health, growth performance, and welfare. The gut microbiota is closely associated with the quality and microbiological safety of foods and food products originating from animals. The gut microbiota of the host can be modulated and enhanced in ways that improve the quality and safety of foods of animal origin. Probiotics—also known as direct-fed microbials—competitive exclusion cultures, prebiotics, and synbiotics have been utilized to achieve this goal. Reducing foodborne pathogen colonization in the gut prior to slaughter and enhancing the chemical, nutritional, or sensory characteristics of foods (e.g., meat, milk, and eggs) are two of many positive outcomes derived from the use of these competitive enhancement–based treatments in food-producing animals.

Expected final online publication date for the Annual Review of Food Science and Technology, Volume 13 is March 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Roles of Nitrocompounds in Inhibition of Foodborne Bacteria, Parasites, and Methane Production in Economic Animals

Simple Summary

Supplementation of nitrocompounds in animal diets has been studied to investigate their effects on economic animals. It has been known that nitrocompounds are capable of inhibiting pathogens, parasites, methane and ammonia production. The toxicity, metabolism, and mechanisms of actions have been discussed in the review to conclude the advantages and disadvantages of application of nitrocompounds in animal production.

Abstract

Nitrocompounds are derivatives of hydrocarbons, alcohols, fatty acids, and esters, consisting one or more nitro functional groups. Either natural sources of nitrocompounds or synthetic chemicals have been applied in animal diets to investigate their effects on economic animals, since conjugates of 3-nitropropanol and 3-nitropropionic acid were isolated from Astragalus oblongifolius. In this review, emphasis will be placed on nitrocompounds’ antimicrobial activity, toxicity, metabolisms and mechanisms of actions. Nitrocompounds can be metabolized by ruminal microbials, such as Denitrobacterium detoxificans, or alcohol dehydrogenase in the liver. Moreover, it has been found that nitrocompounds are capable of inhibiting pathogens, parasites, methane and ammonia production; however, overdose of nitrocompounds could cause methemoglobinemia or interfere with energy production in mitochondria by inhibiting succinate dehydrogenase.

Effects of Essential Oils-Based Supplement and Salmonella Infection on Gene Expression, Blood Parameters, Cecal Microbiome, and Egg Production in Laying Hens

One of the main roles in poultry resistance to infections caused by Salmonella is attributed to host immunity and intestinal microbiota. We conducted an experiment that involved challenging Lohmann White laying hens with Salmonella Enteritidis (SE), feeding them a diet supplemented with an EOs-based phytobiotic Intebio^®. At 1 and 7 days post-inoculation, the expression profiles of eight genes related to immunity, transport of nutrients in the intestine, and metabolism were examined. Cecal microbiome composition and blood biochemical/immunological indices were also explored and egg production traits recorded. As a result, the SE challenge of laying hens and Intebio^® administration had either a suppressive or activating effect on the expression level of the studied genes (e.g., IL6 and BPIFB3), the latter echoing mammalian/human tissue-specific expression. There were also effects of the pathogen challenge and phytobiotic intake on the cecal microbiome profiles and blood biochemical/immunological parameters, including those reflecting the activity of the birds' immune systems (e.g., serum bactericidal activity, β-lysine content, and immunoglobulin levels). Significant differences between control and experimental subgroups in egg performance traits (i.e., egg weight/number/mass) were also found. The phytobiotic administration suggested a positive effect on the welfare and productivity of poultry.

Low Dose Infection of Hens in Lay with Salmonella enterica Serovar Enteritidis from Different Genomic Clades

Salmonella enterica serovar Enteritidis is the leading cause of salmonellosis in people, and modeling of infections in chickens is used to identify intervention strategies. A review of 80 manuscripts encompassing 119 experiments indicated that the mean dose of infection was 10⁸ CFU per bird. Experiments of less than 10⁶ CFU were primarily conducted in immature birds. To address a lack of information on the impact of low dosages on the hen at lay, two experiments were conducted in triplicate. Experiment A addressed issues associated with vaccination; thus, hens were infected intramuscularly at 10³, 10⁵, and 10⁷ CFU. For Experiment B, which was focused more on colonization and invasion, hens were infected orally with 5 × 10³ CFU with 4 strains from different genomic clades. Samples from liver, spleen, ovarian pedicle, and paired ceca in both experiments were cultured 5, 6, 7, and 8 days postinfection. Eggshell microbiome taxa were assessed in Experiment B. Results indicated that dosages of 10³ CFU in both experiments produced enough positive samples to be used within models. The intramuscular route resulted in approximately twice as many positive samples as the oral route. The kinetics of infection appeared to differ between low and high dosages suggestive of a J-curve response. These results could impact risk assessments if the hen at lay has a nonlinear response to infectious dose.

Nitro-treatment of composted poultry litter; effects on Salmonella, E. coli and nitrogen metabolism

Poultry litter is a potentially valuable crude protein feedstuff for ruminants but must be treated to kill pathogens before being fed. Composting kills pathogens but risks losses of nitrogen due to volatilization or leaching as ammonia. Treatment of poultry litter with ethyl nitroacetate, 3-nitro-1-propionate, ethyl 2-nitropropionate (at 27 µmol/g), decreased numbers of experimentally-inoculated Salmonella Typhimurium (>1.0 log₁₀ compared to controls, 4.2 ± 0.2 log₁₀ CFU/g) but not endogenous Escherichia coli early during simulated composting. By day 9 of simulated composting, Salmonella and E. coli were decreased to non-detectable levels regardless of treatment. Some nitro-treatments preserved uric acid and prevented ammonia accumulation, with 18% more uric acid remaining and 17-24% less ammonia accumulating in some nitro-treated litter than in untreated litter (18.1 ± 3.8 µmol/g and 3.4 ± 1.4 µmol/g, respectively). Results indicate that nitro-treatment may help preserve uric acid in composted litter while aiding Salmonella control.

2-Nitro-1-propanol improved nutrient digestibility and oocyst shedding but not growth performance of Eimeria-challenged broilers

A 2 × 3 factorial arrangement study was conducted to evaluate 3 dosages of 2-nitro-1-propanol (NP; 0, 150, and 200 ppm) on intestinal health of birds with or without Eimeria challenge. A total of 432 thirteen-day-old male broiler chickens were randomly allocated to 6 treatments with 8 replicate cages of 9 birds per cage. All birds were fed with treatment diets from day 13 to 21. Birds in the challenge groups were gavaged with Eimeria maxima (50,000 oocysts per bird), Eimeria tenella (50,000 oocysts per bird), and Eimeria acervulina (250,000 oocysts per bird) on day 15. Growth performance was evaluated from day 13 to 21, and gut permeability was measured by fluorescein isothiocyanate dextran on day 20. The intestinal lesion, intestinal morphology, and oocysts shedding were determined at the end of the trial. The linear and quadratic orthogonal polynomial contrasts were used to evaluate the effects of increasing NP doses in responses to Eimeria challenge. The results showed that NP was not able to maintain efficient growth performance but improved gut leakage during Eimeria infection period. On the other hand, Eimeria infection increased gut permeability (P < 0.0001) and reduced ileal digestible energy (IDE) and apparent ileal digestibility (AID) of nitrogen. However, the increase of NP linearly enhanced IDE and AID of nitrogen (P < 0.01). Moreover, an interaction between challenge and linear dosage effects was observed for IDE (P = 0.0066) and AID of nitrogen (P = 0.0462). The results indicated that NP improved nutrient digestibility and reduced total oocysts shedding in birds challenged with Eimeria spp. Besides, higher NP doses numerically improved villi height in the intestine. In summary, NP was not able to maintain growth performance of birds but presented positive outcomes on nutrient digestibility and reduced oocysts shedding during mixed Eimeria infection.

Evaluation of nitro compounds as feed additives in diets of Eimeria-challenged broilers in vitro and in vivo

Coccidiosis is a disease caused by Eimeria spp., resulting in approximately 3 billion US dollar loss in the poultry industry annually. The present study evaluated the effects of potential feed additives, 2-Nitro-1-propanol (NP) and nitroethanol (NE), on control of coccidiosis. An in vitro experiment indicated that both NP and NE inhibited the development of sporozoites in Madin-Darby bovine kidney cells (MDBK). The in vivo study was further conducted to evaluate the effects of NP and NE on growth performance, nitrogen-corrected apparent metabolizable energy (AMEn), and intestinal lesion scores of broilers challenged with Eimeria spps. Six treatments were tested in the study, including the nonchallenged control, challenged control, 100 ppm NP, 200 ppm NP, 100 ppm NE, and 200 ppm NE. Broilers were fed the treatment diets from day 12 until the end of the trial. All birds except the unchallenged control were challenged with Eimeria maxima, Eimeria tenella, and Eimeria acervulina on day 14. The growth performance was calculated, and the intestinal lesion was scored on day 20. The results showed that Eimeria challenge significantly reduced growth performance, increased intestinal lesion scores, and decreased AMEn compared with the nonchallenged control group. Birds fed with 200 ppm of NP had reduced growth performance compared with the nonchallenged control and challenged control. However, the supplementation of NP significantly improved AMEn and reduced cecal damage. Overall, NP and NE reduced sporozoites numbers in the MDBK cells. NP improved dietary digestibility of energy and reduces lesion scores in the ceca but could not maintain growth performance in broiler chickens infected with Eimeria spp.

Infection, colonization and shedding of Campylobacter and Salmonella in animals and their contribution to human disease: A review

Livestock meat and offal contribute significantly to human nutrition as sources of high-quality protein and micronutrients. Livestock products are increasingly in demand, particularly in low- and middle-income settings where economies are growing and meat is increasingly seen as an affordable and desirable food item. Demand is also driving intensification of livestock keeping and processing. An unintended consequence of intensification is increased exposure to zoonotic agents, and a contemporary emerging problem is infection with Campylobacter and Salmonella spp. from livestock (avian and mammalian), which can lead to disease, malabsorption and undernutrition through acute and chronic diarrhoea. This can occur at the farm, in households or through the food chain. Direct infection occurs when handling livestock and through bacteria shed into the environment, on food preparation surfaces or around the house and surroundings. This manuscript critically reviews Campylobacter and Salmonella infections in animals, examines the factors affecting colonization and faecal shedding of bacteria of these two genera as well as risk factors for human acquisition of the infection from infected animals or environment and analyses priority areas for preventive actions with a focus on resource-poor settings.