Dopamine receptor D2 confers colonization resistance via microbial metabolites.

The gut microbiome has major roles in modulating host physiology. One such function is colonization resistance, or the ability of the microbial collective to protect the host against enteric pathogens1-3, including enterohaemorrhagic Escherichia coli (EHEC) serotype O157:H7, an attaching and effacing (AE) food-borne pathogen that causes severe gastroenteritis, enterocolitis, bloody diarrhea and acute renal failure4,5 (haemolytic uremic syndrome). Although gut microorganisms can provide colonization resistance by outcompeting some pathogens or modulating host defence provided by the gut barrier and intestinal immune cells6,7, this phenomenon remains poorly understood. Here, we show that activation of the neurotransmitter receptor dopamine receptor D2 (DRD2) in the intestinal epithelium by gut microbial metabolites produced upon dietary supplementation with the essential amino acid L-tryptophan protects the host against Citrobacter rodentium, a mouse AE pathogen that is widely used as a model for EHEC infection8,9. We further find that DRD2 activation by these tryptophan-derived metabolites decreases expression of a host actin regulatory protein involved in C. rodentium and EHEC attachment to the gut epithelium via formation of actin pedestals. Our results reveal a noncanonical colonization resistance pathway against AE pathogens that features an unconventional role for DRD2 outside the nervous system in controlling actin cytoskeletal organization in the gut epithelium. Our findings may inspire prophylactic and therapeutic approaches targeting DRD2 with dietary or pharmacological interventions to improve gut health and treat gastrointestinal infections, which afflict millions globally.

Combating Staphylococcus aureus biofilm formation: the inhibitory potential of tormentic acid and 23-hydroxycorosolic acid.

Plant extracts have been used to treat microbiological diseases for centuries. This study examined plant triterpenoids tormentic acid (TA) and 23-hydroxycorosolic acid (HCA) for their antibiofilm effects on Staphylococcus aureus strains (MTCC-96 and MTCC-7405). Biofilms are bacterial colonies bound by a matrix of polysaccharides, proteins, and DNA, primarily impacting healthcare. As a result, ongoing research is being conducted worldwide to control and prevent biofilm formation. Our research showed that TA and HCA inhibit S. aureus planktonic growth by depolarizing the bacterial membrane. In addition, zone of inhibition studies confirmed their effectiveness, and crystal violet staining and biofilm protein quantification confirmed their ability to prevent biofilm formation. TA and HCA exhibited substantial reductions in biofilm formation for S. aureus (MTCC-96) by 54.85% and 48.6% and for S. aureus (MTCC-7405) by 47.07% and 56.01%, respectively. Exopolysaccharide levels in S. aureus biofilm reduced significantly by TA (25 µg/mL) and HCA (20 µg/mL). Microscopy, bacterial motility, and protease quantification studies revealed their ability to reduce motility and pathogenicity. Furthermore, TA and HCA treatment reduced the mRNA expression of S. aureus virulence genes. In silico analysis depicted a high binding affinity of triterpenoids for biofilm and quorum-sensing associated proteins in S. aureus, with TA having the strongest affinity for TarO (- 7.8 kcal/mol) and HCA for AgrA (- 7.6 kcal/mol). TA and HCA treatment reduced bacterial load in S. aureus-infected peritoneal macrophages and RAW264.7 cells. Our research indicates that TA and HCA can effectively combat S. aureus by inhibiting its growth and suppressing biofilm formation.

Consequences of supplementing duck's diet with charcoal on carcass criteria, meat quality, nutritional composition, and bacterial load.

The influence of charcoal as feed additives on carcass and meat characteristics was studied in 144 four weeks old Muller ducks. The experimental ducklings were assigned to six groups of 24 birds (Eight per replicates each). The dietary treatments contained 0, 0.5, 1.0, 1.5, 2.0, and 2.5% charcoal for G1 (C), G2 (L1), G3 (L2), G4 (L3), G5 (L4) and G6 (L5), respectively. All experimental birds were raised under similar environmental and managerial conditions. Results indicated that charcoal did not affect most carcass traits significantly except for dressing percentage was higher (P < 0.05) in 1.5 and 2 % charcoal included ducks diets compared to control ducks. Charcoal supplementation significantly affected duck meat tenderness, juiciness and water holding capacity. Moreover, charcoal altered (P < 0.05) meat components such as crude protein, calcium components, desirable fatty acids, nutritional value and some bacterial counts. Thiobarbituric acid reactive substances reduced in birds fed charcoal at 1.5, 2, and 2.5%, with significant variation among treatments. No significant differences in the number of Escherichia coli and Staphylococcus aureus were detected among the ducks fed with charcoal and the control group. It could be concluded that charcoal could be included in ducks' diets at 1.5 and 2% with beneficial effects on carcass parameters.

Exploration of Zingiber officinale effects on growth performance, immunity and gut morphology in broilers / Exploração dos efeitos do Zingiber officinale no desempenho de crescimento, imunidade e morfologia intestinal em frangos de corte

The current study aimed to determine the effects of different levels of Zingiber officinale as a herbal feed additive on growth performance, carcass characteristic, serum biochemistry, total bacterial count (TBC), gut morphology, and immunological parameters of broilers. A total of 1500, day-old broiler chicks (Hubbard) were equally accredited to five treatment groups, each with six replicates (50 birds/replicate). Five experimental diets were prepared using basal diet i.e. with antibiotics positive control (PC), 3 g/kg ginger (group A), 6 g/kg ginger (group B), 9 g/kg ginger (group C) and without antibiotics negative control (NC). Group A and C showed significantly (p<0.05) higher feed intake (FI) as compared to other groups. Group C showed significantly (p<0.05) lower Total bacterial count (TBC) followed by group B as compared to NC. Carcass characteristics showed non-significant effects among different treatments. Mean villi length and width were significantly (p <0.05) higher in all ginger supplemented groups as compared to the control groups. Blood serum parameters including cholesterol, triglycerides, and low density lipoproteins (LDL) were significantly (p<0.05) lower in groups B and C in comparison with the control groups. Whereas high-density lipoproteins (HDL) was significantly higher in group B as compared to the others. In conclusion, ginger supplementation @0.6% in the basal diet significantly improved growth performance and gut morphometry of broilers. It also showed a positive impact on cholesterol, triglycerides and gut microbes. Therefore, ginger could be a better substitute for antibiotic growth promoters.

O presente estudo teve como objetivo determinar os efeitos de diferentes níveis de Zingiber officinale como aditivo à base de plantas medicinais sobre o desempenho de crescimento, características da carcaça, bioquímica sérica, contagem bacteriana total (CBT), morfologia intestinal e parâmetros imunológicos de frangos de corte. Um total de 1.500 pintos de corte de um dia de idade (Hubbard) foram igualmente credenciados em cinco grupos de tratamento, cada um com seis repetições (50 aves/repetição). Cinco dietas experimentais foram preparadas usando dieta basal, ou seja, com controle positivo de antibióticos (PC), 3 g/kg de gengibre (grupo A), 6 g/kg de gengibre (grupo B), 9 g/kg de gengibre (grupo C) e sem controle negativo de antibióticos (NC). Os grupos A e C apresentaram consumo de ração (FI) significativamente (p < 0,05) maior do que os outros grupos. O grupo C apresentou contagem bacteriana total (CBT) significativamente menor (p < 0,05) seguido pelo grupo B em comparação com o NC. As características da carcaça apresentaram efeitos não significativos entre os diferentes tratamentos. O comprimento e largura médios das vilosidades foram significativamente (p < 0,05) maiores em todos os grupos suplementados com gengibre em comparação com os grupos de controle. Os parâmetros séricos do sangue, incluindo colesterol, triglicerídeos e lipoproteínas de baixa densidade (LDL), foram significativamente (p < 0,05) menores nos grupos B e C em comparação com os grupos controle. Enquanto as lipoproteínas de alta densidade (HDL) foram significativamente maiores no grupo B em comparação com os outros. Em conclusão, a suplementação de gengibre a 0,6% na dieta basal melhorou significativamente o desempenho de crescimento e a morfometria intestinal de frangos de corte. Ele também mostrou um impacto positivo sobre o colesterol, triglicerídeos e micróbios intestinais. Portanto, o gengibre pode ser um substituto melhor para os promotores de crescimento com antibióticos.

Enterococcus faecium supplementation prevents enteritis caused by Escherichia coli in goats.

The probiotic Enterococcus faecium is a gut microbe with immunomodulatory effects, which has been widely used to prevent diarrhoea in pigs and birds. Escherichia coli is a common pathogen that causes inflammatory bowel disease in animals. The aim of this study was to investigate the protective effects of E. faecium on enteritis in goats. Forty goats were randomly divided into 4 treatment groups: control, E. faecium, E. coli, and E. faecium + E. coli. The changes of physiological indicators and diarrhoea scoring were evaluated on days -4, -2, 0, 2, 4, 6, and 8. The pathological examination, inflammatory cytokines mRNA expression and bacterial counts in jejunum and caecum were detected on day 4 and 8. The results showed that body temperature, respiratory rate, heart rate and leukocyte counts all increased from the 2nd to the 6th day after feeding with E. coli, and the diarrhoea score was significantly increased. However, E. faecium-pretreated goats had lower body temperatures and fewer leukocytes than E. coli-treated goats on day 2, as well as decreased diarrhoea scores. E. coli treatment caused histopathological damage and morphological changes in the jejunum and caecum, while pretreatment with E. faecium significantly alleviated these injuries. E. faecium pretreatment can reduce the load of E. coli and increase the prevalence of Lactobacillus, thereby balancing the microbiota in the intestine. Furthermore, E. coli-infected goats pretreated with E. faecium showed obvious inhibition of Toll-like receptor 4, interleukin (IL)-1ß, IL-6, IL-8 and tumour necrosis factor-α mRNA expression in the jejunum and caecum compared to that in the E. coli treatment group. In conclusion, the addition of E. faecium to goat feed is beneficial for improving clinical symptoms, maintaining intestinal mucosa integrity, balancing the microbiota and decreasing inflammatory responses in E. coli-induced intestinal injury.

Immunization with a tri-antigen syphilis vaccine significantly attenuates chancre development, reduces bacterial load, and inhibits dissemination of Treponema pallidum.

Syphilis continues to be a significant public health concern worldwide. The disease is endemic in many low- and middle-income countries, and rates have risen sharply in high-income countries over the last decade. The continued prevalence of infectious and congenital syphilis worldwide highlights the need for the development of an effective syphilis vaccine to complement public health measures for syphilis control. The complex, multi-stage course of syphilis infection necessitates a holistic approach to the development of an effective vaccine, in which immunization prevents both the localized stage of infection (typified by the highly infectious chancre) and the disseminated stages of infection (typified by the secondary rash, neurosyphilis, and destructive tertiary lesions, as well as congenital syphilis). Inhibiting development of the infectious chancre would reduce transmission thus providing community- level protection, while preventing dissemination would provide individual-level protection by reducing serious sequelae and may also provide community level protection by reducing shedding during secondary syphilis. In the current study we build upon prior investigations which demonstrated that immunizations with individual, well characterized T. pallidum TprK, TprC, and Tp0751 peptides elicits partial protection against infection in the animal model. Specifically, we show here that immunization with a TprC/TprK/Tp0751 tri-antigen cocktail protects animals from progressive syphilis lesions and substantially inhibits dissemination of the infection.

Preventative treatment with Fluorothiazinon suppressed Acinetobacter baumannii-associated septicemia in mice.

The high prevalence of multidrug-resistant Acinetobacter baumannii has emerged as a serious problem in the treatment of nosocomial infections in the past three decades. Recently, we developed a new small-molecule inhibitor belonging to a class of 2,4-disubstituted-4H-[1,3,4]-thiadiazine-5-ones, Fluorothiazinon (FT, previously called CL-55). FT effectively suppressed the T3SS of Chlamydia spp., Pseudomonas aeruginosa, and Salmonella sp. without affecting bacterial growth in vitro. In this study, we describe that prophylactic use of FT for 4 days prior to challenge with resistant clinical isolates of A. baumannii (ABT-897-17 and 52TS19) suppressed septic infection in mice, resulting in improved survival, limited bacteraemia and decreased bacterial load in the organs of the mice. We show that FT had an inhibitory effect on A. baumannii biofilm formation in vitro and, to a greater extent, on biofilm maturation. In addition, FT inhibited Acinetobacter isolate-induced death of HeLa cells, which morphologically manifested as apoptosis. The mechanism of FT action on A. baumannii is currently being studied. FT may be a promising candidate for the development of a broad-spectrum anti-virulence drug to use in the prevention of nosocomial infections.

A multistep enrichment process with custom growth medium improves resuscitation of chlorine-stressed coliforms from secondary sewage effluents.

Resuscitation and detection of stressed total coliforms in chlorinated water samples is needed to assess and prevent health effects from adverse exposure. In this study, we report that the addition of a growth enhancer mix consisting of trehalose, sodium pyruvate, magnesium chloride, and 1× trace mineral supplement improved growth of microorganisms from chlorinated secondary effluent in the base medium with Colilert-18. Improving growth of chlorine stressed microorganisms from secondary effluent is crucial to decreased detection time from 18 to 8 h.

Unraveling of Chlorella-associated bacterial load, diversity, and their imputed functions at high- and low-yield conditions through metagenome sequencing.

Chlorella-associated bacteria can have a significant influence on facilitating higher Chlorella biomass yield due to their symbiotic relationship. In this study, non-axenic Chlorella was cultivated in an airlift photobioreactor at high and low-yield conditions. The associated bacterial diversity was analyzed using 16S rRNA metagenome sequencing. At high-yield conditions, the bacterial load was observed in the range of 108 -1010 CFU · mL-1 , whereas at low-yield conditions, bacteria were more dominant and observed in the range of 1014 -1015 CFU · mL-1 . The majority of the bacterial species associated with Chlorella at high-yield conditions belongs to Proteobacteria and Bacteroidetes. Further, Bacteroidetes levels were decreased at low-yield conditions and were highly diversified with Planctomycetes, Firmicutes, and 18 others. Predicted functional genes indicated that Chlorella-associated bacteria have the enzymes involved in the metabolism and biosynthesis of B-complex vitamins (i.e., vitamin B12 , thiamin, biotin, pyridoxine, and riboflavin). A critical evaluation revealed that vitamin biosynthesis genes were more abundant at low-yield conditions; however, vitamin B12 transport genes (B12 transport ATP-binding protein, B12 substrate-binding transportation, and B12 permease protein) were less abundant, indicating even though vitamins production occurs, but their availability to Chlorella was limited due to the lack of vitamin transport genes. Further, at high yield, Chlorella-associated bacteria enabled higher growth by supplementing the vitamins. In contrast, at low-yield condition-an increased bacterial load, diversity, and limited vitamin transport functional genes affected the Chlorella yield. It can be inferred that Chlorella yield was significantly affected by three factors: associated bacterial load, diversity, and transport functional genes of vitamins.

Lumpfish (Cyclopterus lumpus) Is Susceptible to Renibacterium salmoninarum Infection and Induces Cell-Mediated Immunity in the Chronic Stage.

Renibacterium salmoninarum is a Gram-positive, intracellular pathogen that causes Bacterial Kidney Disease (BKD) in several fish species in freshwater and seawater. Lumpfish (Cyclopterus lumpus) is utilized as a cleaner fish to biocontrol sea lice infestation in Atlantic salmon (Salmo salar) farms. Atlantic salmon is susceptible to R. salmoninarum, and it can transfer the infection to other fish species. Although BKD outbreaks have not been reported in lumpfish, its susceptibility and immune response to R. salmoninarum is unknown. In this study, we evaluated the susceptibility and immune response of lumpfish to R. salmoninarum infection. Groups of lumpfish were intraperitoneally (i.p.) injected with either R. salmoninarum (1×107, 1×108, or 1×109 cells dose-1) or PBS (control). R. salmoninarum infection kinetics and mortality were followed for 98 days post-infection (dpi). Transcript expression levels of 33 immune-relevant genes were measured in head kidney (n = 6) of fish infected with 1×109 cells/dose and compared to the control at 28 and 98 dpi. Infected lumpfish displayed characteristic clinical signs of BKD. Lumpfish infected with high, medium, and low doses had a survival rate of 65%, 93%, and 95%, respectively. Mortality in the high-dose infected group stabilized after 50 dpi, but R. salmoninarum persisted in the fish tissues until 98 dpi. Cytokines (il1ß, il8a, il8b), pattern recognition receptors (tlr5a), interferon-induced effectors (rsad2, mxa, mxb, mxc), and iron regulation (hamp) and acute phase reactant (saa5) related genes were up-regulated at 28 dpi. In contrast, cell-mediated adaptive immunity-related genes (cd4a, cd4b, ly6g6f, cd8a, cd74) were down-regulated at 28 dpi, revealing the immune suppressive nature of R. salmoninarum. However, significant upregulation of cd74 at 98 dpi suggests induction of cell-mediated immune response. This study showed that R. salmoninarum infected lumpfish in a similar fashion to salmonid fish species and caused a chronic infection, enhancing cell-mediated adaptive immune response.

Evaluating the effects of a dietary synbiotic or synbiotic plus enhanced organic acid on broiler performance and cecal and carcass Salmonella load.

Several feed additives such as synbiotics and organic acids may be viable options for controlling Salmonella in poultry. This experiment was conducted to study the effects of synbiotic product or synbiotic plus enhanced organic acid program on broiler performance, intestinal histomorphology, and cecal and carcass Salmonella load. A total of 648 day-of-hatch Cobb 700 male broiler chicks were randomly allocated to one of 4 dietary treatments: basal control diet (CON), CON diet supplemented with a synbiotic (PoultryStar; 500 g/MT; PS), CON diet supplemented with PS in the starter phase and enhanced organic acid (Biotronic PX Top3 US; 500g/MT; BPX) in the grower and finisher phase (PS1+BPX2), and the CON diet supplemented with PS in the starter and grower phase and BPX in the finisher phase (PS2+BPX1). No differences in overall BW or BWG (P > 0.05) were observed among PS, PS1+BPX2, and PS2+BPX1; however, BW was consistently greater (P < 0.05) in PS, PS1+BPX2, and PS2+BPX1 compared with CON on d 14 28, 35, and 42. On d 1 to 14 and d 1 to 28, PS and PS2+BPX1 improved FCR compared to CON (P < 0.05); PS1+BPX2 had intermediate results. No differences (P > 0.05) in overall FI were observed among dietary treatments, although PS1+BP2 and PS2+BPX1 increased FI numerically compared to CON and PS. Both PS1+BPX2 and PS2+BPX1 had reduced carcass Salmonella load by 1.6 and 1.4 log units, respectively, compared with CON (P < 0.05); PS had intermediate results. Birds fed PS1+BPX2 and PS2+BPX1 reduced the percentage of postchilled carcasses that tested positive for Salmonella by 72% and 57%, respectively, compared to CON, while PS had intermediate results with a 43% reduction. This experiment demonstrated that dietary supplementation with synbiotic or synbiotic plus organic acid can be used as a potential tool to improve growth performance and reduce carcass Salmonella in broilers.

Chitosan propolis nanocomposite alone or in combination with apramycin: an alternative therapy for multidrug-resistant Salmonella Typhimurium in rabbits: in vitro and in vivo study.

Introduction. The emergence of multidrug-resistant Salmonella Typhimurium strains has increased the need for safe, alternative therapies from natural sources with antibacterial properties.Hypothesis/Gap Statement. There are no published data regarding the use of chitosan propolis nanocomposite (CPNP) either alone or in combination with antibiotics as antimicrobials against S. Typhimurium, especially in Egypt.Aim. This study evaluated the antibacterial activities of five antimicrobials [apramycin, propolis, chitosan nanoparticles (CNPs), chitosan propolis nanocomposite (CPNP) and CPNP +apramycin] against ten virulent and multidrug-resistant (MDR) S. Typhimurium field strains recovered from diarrheic rabbits through in vitro and in vivo study.Methodology. The expression levels of three virulence genes of S. Typhimurium strains were determined by quantitative reverse-transcription PCR (RT-qPCR) after exposure to sub-inhibitory concentrations of apramycin, propolis, CNPs, CPNP alone, and CPNP +apramycin. Additionally, 90 New Zealand rabbits were divided into control and experimentally S. Typhimurium-infected groups. The infected rabbits were orally administered saline solution (infected-untreated); 10 mg apramycin/kg (infected-apramycin-treated); 50 mg propolis/kg (infected-propolis-treated); 15 mg CPNP/kg (infected-CPNP-treated) and 15 mg CPNP +10 mg apramycin/kg (infected-CPNP +apramycin-treated) for 5 days.Results. The RT-qPCR analysis revealed different degrees of downregulation of all screened genes. Furthermore, the treatment of infected rabbits with CPNP or CPNP +apramycin significantly improved performance parameters, and total bacterial and Salmonella species counts, while also modulating both oxidative stress and altered liver and kidney parameters.Conclusion. This work demonstrates the use of CPNP alone or in combination with apramycin in the treatment of S. Typhimurium in rabbits.

Florfenicol Enhances Colonization of a Salmonella enterica Serovar Enteritidis floR Mutant with Major Alterations to the Intestinal Microbiota and Metabolome in Neonatal Chickens.

Florfenicol is an important antibiotic commonly used in poultry production to prevent and treat Salmonella infection. However, oral administration of florfenicol may alter the animals' natural microbiota and metabolome, thereby reducing intestinal colonization resistance and increasing susceptibility to Salmonella infection. In this study, we determined the effect of florfenicol (30 mg/kg of body weight) on gut colonization of neonatal chickens challenged with Salmonella enterica subsp. enterica serovar Enteritidis. We then analyzed the microbial community structure and metabolic profiles of cecal contents using microbial 16S amplicon sequencing and liquid chromatography-mass spectrometry (LC-MS) untargeted metabolomics, respectively. We also screened the marker metabolites using a multi-omics technique and assessed the effect of these markers on intestinal colonization by S. Enteritidis. Florfenicol administration significantly increased the loads of S. Enteritidis in cecal contents, spleen, and liver and prolonged the residence of S. Enteritidis. Moreover, florfenicol significantly affected cecal colony structures, with reduced abundances of Lactobacillus and Bacteroidetes and increased levels of Clostridia, Clostridium, and Dorea. The metabolome was greatly influenced by florfenicol administration, and perturbation in metabolic pathways related to linoleic acid metabolism (linoleic acid, conjugated linoleic acid [CLA], 12,13-EpOME, and 12,13-diHOME) was most prominently detected. We screened CLA and 12,13-diHOME as marker metabolites, which were highly associated with Lactobacillus, Clostridium, and Dorea. Supplementation with CLA maintained intestinal integrity, reduced intestinal inflammation, and accelerated Salmonella clearance from the gut and remission of enteropathy, whereas treatment with 12,13-diHOME promoted intestinal inflammation and disrupted intestinal barrier function to sustain Salmonella infection. Thus, these results highlight that florfenicol alters the intestinal microbiota and metabolism of neonatal chickens and promotes Salmonella infection mainly by affecting linoleic acid metabolism. IMPORTANCE Florfenicol is a broad-spectrum fluorine derivative of chloramphenicol frequently used in poultry to prevent/treat Salmonella. However, oral administration of florfenicol may lead to alterations in the microbiota and metabolome in the chicken intestine, thereby reducing colonization resistance to Salmonella infection, and the possible mechanisms linking antibiotics and Salmonella colonization in poultry have not yet been fully elucidated. In the current study, we show that increased colonization by S. Enteritidis in chickens administered florfenicol is associated with large shifts in the gut microbiota and metabolic profiles. The most influential linoleic acid metabolism is highly associated with the abundances of Lactobacillus, Clostridium, and Dorea in the intestine. The screened target metabolites in linoleic acid metabolism affect S. Enteritidis colonization, intestinal inflammation, and intestinal barrier function. Our findings provide a better understanding of the susceptibility of animal species to Salmonella after antibiotic intervention, which may help to elucidate infection mechanisms that are important for both animal and human health.

Responses of Escherichia coli and Listeria monocytogenes to ozone treatment on non-host tomato: Efficacy of intervention and evidence of induced acclimation.

Because of the continuous rise of foodborne illnesses caused by the consumption of raw fruits and vegetables, effective post-harvest anti-microbial strategies are necessary. The aim of this study was to evaluate the anti-microbial efficacy of ozone (O3) against two common causes of fresh produce contamination, the Gram-negative Escherichia coli O157:H7 and Gram-positive Listeria monocytogenes, and to relate its effects to potential mechanisms of xenobiosis by transcriptional network modeling. The study on non-host tomato environment correlated the dose × time aspects of xenobiosis by examining the correlation between bacterial survival in terms of log-reduction and defense responses at the level of gene expression. In E. coli, low (1 µg O3/g of fruit) and moderate (2 µg O3/g of fruit) doses caused insignificant reduction in survival, while high dose (3 µg/g of fruit) caused significant reduction in survival in a time-dependent manner. In L. monocytogenes, moderate dose caused significant reduction even with short-duration exposure. Distinct responses to O3 xenobiosis between E. coli and L. monocytogenes are likely related to differences in membrane and cytoplasmic structure and components. Transcriptome profiling by RNA-Seq showed that primary defenses in E. coli were attenuated after exposure to a low dose, while the responses at moderate dose were characterized by massive upregulation of pathogenesis and stress-related genes, which implied the activation of defense responses. More genes were downregulated during the first hour at high dose, with a large number of such genes getting significantly upregulated after 2 hr and 3 hr. This trend suggests that prolonged exposure led to potential adaptation. In contrast, massive downregulation of genes was observed in L. monocytogenes regardless of dose and exposure duration, implying a mechanism of defense distinct from that of E. coli. The nature of bacterial responses revealed by this study should guide the selection of xenobiotic agents for eliminating bacterial contamination on fresh produce without overlooking the potential risks of adaptation.

Baseline iron status and presence of anaemia determine the course of systemic Salmonella infection following oral iron supplementation in mice.

BACKGROUND: Iron deficiency anaemia (IDA) is a major health concern. However, preventive iron supplementation in regions with high burden of infectious diseases resulted in an increase of infection related morbidity and mortality. METHODS: We fed male C57BL/6N mice with either an iron deficient or an iron adequate diet. Next, they received oral iron supplementation or placebo followed by intraperitoneal infection with Salmonella Typhimurium (S.Tm). FINDINGS: We found that mice with IDA had a poorer clinical outcome than mice on an iron adequate diet. Interestingly, iron supplementation of IDA mice resulted in higher bacterial burden in organs and shortened survival. Increased transferrin saturation and non-transferrin bound iron in the circulation together with low expression of ferroportin facilitated the access of the pathogen to iron and promoted bacterial growth. Anaemia, independent of iron supplementation, was correlated with reduced neutrophil counts and cytotoxic T cells. With iron supplementation, anaemia additionally correlated with increased splenic levels of the cytokine IL-10, which is suggestive for a weakened immune control to S.Tm infection. INTERPRETATION: Supplementing iron to anaemic mice worsens the clinical course of bacterial infection. This can be traced back to increased iron delivery to bacteria along with an impaired anti-microbial immune response. Our findings may have important implications for iron supplementation strategies in areas with high endemic burden of infections, putting those individuals, who potentially profit most from iron supplementation for anaemia, at the highest risk for infections. FUNDING: Financial support by the Christian Doppler Laboratory for Iron Metabolism and Anemia Research.

Cinnamomum cassia and Syzygium aromaticum Essential Oils Reduce the Colonization of Salmonella Typhimurium in an In Vivo Infection Model Using Caenorhabditis elegans.

The regulation of intestinal colonization in livestock by means of non-bactericidal additives is an important management lever for zoonotic bacteria such as Salmonella spp. Caenorhabditis elegans is proposed here as a model for the evaluation of five essential oils (EOs) as anti-colonization products against Salmonella Typhimurium. An evaluation of the toxicity of EOs for C. elegans showed LD50 values ranging from 74.5 ± 9.6 µg/mL for Cinnamomum cassia (CEO) to 271.6 ± 14.9 µg/mL for Syzygium aromaticum (SyEO). Both EOs significantly inhibited bacterial colonization in the digestive tract of C. elegans with reductions of 0.88 and 0.70 log CFU/nematode at nontoxic concentrations of 50 µg/mL and 150 µg/mL, respectively. With the minimal bactericidal concentrations of CEO and SyEO against S. Typhimurium being 312.5 µg/mL and 625 µg/mL, respectively, an antibacterial effect can be excluded to explain the inhibition of the bacterial load. The anti-colonizing activity of these two EOs could, however, be related to an inhibition of the swimming motility, which was significantly reduced by 23.47% for CEO at 50 µg/mL and 19.56% for SyEO at 150 µg/mL. This study shows the potential of C. elegans as a predictive in vivo model of anti-colonizing activities that is suitable for the evaluation of essential oils.

Risk factors for poor colostrum quality and failure of passive transfer in Scottish dairy calves.

Failure of passive transfer (FPT) has health, welfare and economic implications for calves. Immunoglobulin G (IgG) concentration of 370 dairy calf serum samples from 38 Scottish dairy farms was measured via radial immunodiffusion (RID) to determine FPT prevalence. IgG concentration, total bacteria count (TBC) and total coliform count (TCC) of 252 colostrum samples were also measured. A questionnaire was completed at farm enrollment to investigate risk factors for FPT and poor colostrum quality at farm-level. Multivariable mixed effect logistic and linear regressions were carried out to determine significant risk factors for FPT and colostrum quality. Prevalence of FPT at calf level was determined to be 14.05%. Of 252 colostrum samples, 111 (44.05%) failed to meet Brix thresholds for colostrum quality. Of these 28 and 38 samples also exceeded TBC and TCC thresholds, respectively. Increased time between parturition and colostrum harvesting was numerically (non-significantly) associated with a colostrum Brix result <22%, and increased time spent in a bucket prior to feeding or storing was significantly associated with high TBC (≥100 000 cfu/ml and also ≥10 000 cfu/ml). High TBC values in colostrum were significantly associated with lower serum IgG concentrations. This study highlights associations between colostrum quality and FPT in dairy calves as well as potential risk factors for reduced colostrum quality; recommending some simple steps producers can take to maximise colostrum quality on farm.

Changes in chilled beef packaged in starch film containing sea buckthorn pomace extract and quality changes in the film during super-chilled storage.

This study aimed to evaluate the effects of super-chilled storage (-1.3 °C) combined with starch film packaging containing different contents of sea buckthorn pomace extract (SSF, 0, 1, 2, and 3%, w/w) on the quality of chilled beef. The release kinetics, microstructure, and mechanical properties of the film were also measured to investigate its suitability for super-chilled storage. The results of the meat quality assessment showed that the L*, a*, and sensory evaluation values of the SSF-3% samples were significantly higher (P < 0.05), and the pH, b*, thiobarbituric acid reactive substance (TBARS), total volatile basic nitrogen (TVB-N), and total viable count (TCA) were significantly lower (P < 0.05) than the SSF-0%. The release of SBP from the SSF film was controlled by diffusion. Furthermore, SSF-3% was found to have a compact microstructure and good mechanical properties at the end of the super-chilled storage. The results demonstrated that SSF is an effective packaging material for beef at super-chilling temperatures.

Effect of biochanin A on the rumen microbial community of Holstein steers consuming a high fiber diet and subjected to a subacute acidosis challenge.

Subacute rumen acidosis (SARA) occurs when highly fermentable carbohydrates are introduced into the diet, decreasing pH and disturbing the microbial ecology of the rumen. Rumen amylolytic bacteria rapidly catabolize starch, fermentation acids accumulate in the rumen and reduce environmental pH. Historically, antibiotics (e.g., monensin, MON) have been used in the prevention and treatment of SARA. Biochanin A (BCA), an isoflavone produced by red clover (Trifolium pratense), mitigates changes associated with starch fermentation ex vivo. The objective of the study was to determine the effect of BCA on amylolytic bacteria and rumen pH during a SARA challenge. Twelve rumen fistulated steers were assigned to 1 of 4 treatments: HF CON (high fiber control), SARA CON, MON (200 mg d-1), or BCA (6 g d-1). The basal diet consisted of corn silage and dried distiller's grains ad libitum. The study consisted of a 2-wk adaptation, a 1-wk HF period, and an 8-d SARA challenge (d 1-4: 40% corn; d 5-8: 70% cracked corn). Samples for pH and enumeration were taken on the last day of each period (4 h). Amylolytic, cellulolytic, and amino acid/peptide-fermenting bacteria (APB) were enumerated. Enumeration data were normalized by log transformation and data were analyzed by repeated measures ANOVA using the MIXED procedure of SAS. The SARA challenge increased total amylolytics and APB, but decreased pH, cellulolytics, and in situ DMD of hay (P < 0.05). BCA treatment counteracted the pH, microbiological, and fermentative changes associated with SARA challenge (P < 0.05). Similar results were also observed with MON (P < 0.05). These results indicate that BCA may be an effective alternative to antibiotics for mitigating SARA in cattle production systems.

Biopreservative efficacy of grape (Vitis vinifera) and clementine mandarin orange (Citrus reticulata) by-product extracts in raw ground beef patties.

Beef patties were treated with 450 µg/g of extracts from grape (Vitis vinifera) seeds (GSE), pomace (GPE) or orange (Citrus reticulata) pomace (OPE) and compared to negative (no extract; CTR) and positive (sodium metabisulphite; SMB) controls for their effect on colour, lipid and protein oxidation and bacterial growth under simulated retail display conditions (4 °C) for 9 d, and sensory quality. Antioxidant activity and redness of beef patties increased in the order of CTR < OPE = GPE < GSE < SMB. The order of thiobarbituric acid reactive substances and carbonyl values were CTR > GPE = OPE > GSE > SBM, while that of bacterial counts were CTR > GSE = GPE > OPE > SMB. Retail display period had significant effect on all the shelf-life parameters. Overall, intensity of aroma, beef-like aroma and flavour in beef patties were highest in OPE. Results suggested that GSE and OPE could be commercially valorised as natural antioxidants and antibacterials in beef patties, respectively.