Experimental models of porcine post-weaning colibacillosis and their relationship to post-weaning diarrhoea and digestive disorders as encountered in the field

Impact of precursor-derived peracetic acid on post-weaning diarrhea, intestinal microbiota, and predicted microbial functional genes in weaned pigs

Post-weaning diarrhea affects piglets in the nursery phase of production, leading to a substantial impact both at the farm and financial levels. The multifactorial etiology of this disease includes housing conditions, pig genetics, microbial composition, and metagenomic assets. Among the common therapeutic approaches, the widely used zinc oxide underwent a European Union ban in 2022 due to its negative environmental impact and correlation to increased antimicrobial resistance. During this study, we have tested two levels of inclusion of the potential antimicrobial alternative peracetic acid, delivered in water via the hydrolysis of the precursors sodium percarbonate and tetraacetylethylenediamine, in comparison to zinc oxide and an untreated control during a 2-week animal study. We assessed the microbial composition and predicted the metagenome, together with performance and physiological parameters, in order to describe the microbial functional role in etiopathology. Both zinc oxide and peracetic acid resulted in amelioration of the diarrheal status by the end of the trial period, with noticeable zinc oxide effects visible from the first week. This was accompanied by improved performance when compared to the first-week figures and a decreased stomach pH in both peracetic acid levels. A significant reduction in both stomach and caecal Proteobacteria was recorded in the zinc oxide group, and a significant reduction of Campylobacter in the stomach was reported for both zinc oxide and one of the peracetic acid concentrations. Among other functional differences, we found that the predicted ortholog for the zonula occludens toxin, a virulence factor present in pathogens like Escherichia coli and Campylobacter jejuni, was less abundant in the stomach of treated pigs compared to the control group. In water, peracetic acid delivered via precursor hydrolysis has the potential to be a valid intervention, an alternative to antimicrobial, to assist the weaning of piglets. Our findings support the view that post-weaning diarrhea is a complex multifactorial disease with an important metagenomic component characterized by the differential abundance of specific predicted orthologs and microbial genera in the stomach and caecum of pigs.

Zinc status and indicators of intestinal health in enterotoxigenic Escherichia coli F18 challenged newly weaned pigs fed diets with different levels of zinc

This study investigated the impact of an enterotoxigenic Escherichia coli (ETEC) F18 challenge on newly weaned pigs when fed one of three Zn levels (150, 1,400, or 2,500 ppm) on performance, Zn status, ETEC shedding, and diarrhea. The ETEC challenge was hypothesized to have a more pronounced negative impact on pigs fed a diet containing 150 ppm Zn compared to 1,400 or 2,500 ppm Zn for 14 d after weaning. The study included 72 ETEC F18 susceptible pigs weaned at ~28 d of age (d 0 of the study). The pigs were distributed according to initial weight and litter to one of the three dietary Zn levels. Half of the pigs were challenged with ETEC on d 1 and 2. The challenge reduced (P ≤ 0.03) feed intake and average daily gain (ADG) during d 3 to 5. Challenged pigs fed 150 ppm Zn had lower (P = 0.01) ADG during d 5 to 7 compared to those fed 1,400 or 2,500 ppm Zn, whereas control pigs' ADG were not affected by dietary Zn content. Challenged pigs fed 150 ppm Zn also showed lower (P < 0.01) fecal dry matter (DM) on d 5 compared to control pigs fed 150 ppm Zn and challenged pigs fed 1,400 or 2,500 ppm Zn. Challenge increased (P < 0.01) ETEC shedding in all groups, but challenged pigs fed 150 ppm Zn showed higher (P ≤ 0.05) fecal shedding of ETEC and toxins than when fed 1,400 or 2,500 ppm. On d 3, C-reactive protein concentration in plasma was lower (P < 0.03) for pigs fed 1,400 and 2,500 compared to 150 ppm Zn. Plasma haptoglobin and pig major acute phase protein were unaffected by dietary Zn content. On d 0, the serum Zn concentration was 586 ± 36.6 µg/L, which pigs fed 150 ppm Zn maintained throughout the study. The serum Zn concentration increased (P ≤ 0.07) in pigs fed 1,400 or 2,500 ppm Zn. The challenge decreased (P < 0.01) the serum Zn concentration in pigs fed 2,500 ppm Zn. On d 5 and 7, serum Zn concentration was similar for challenged pigs fed 1,400 and 2,500 ppm Zn, while control pigs fed 2,500 ppm Zn had higher (P < 0.01) serum Zn concentration than 1,400 ppm Zn. On d 7, serum Zn concentration tended (P = 0.08) to be lower for pigs with diarrhea (fecal DM ≤ 18%). In summary, these results indicate that newly weaned pigs fed 150 ppm Zn are more susceptible to ETEC F18 colonization and its adverse consequences such as diarrhea and reduced growth, even though challenge did not increase acute phase proteins.

Pre-Treatment with Bromelain Prevents Intestinal Dysbiosis in Pigs with Post-Weaning Diarrhea, without Increasing Antimicrobial Resistance in Escherichia coli

Pigs are especially vulnerable to intestinal pathogens and dysbiosis in the first two weeks after weaning. Infection with enterotoxigenic strains of Escherichia coli (ETEC) in combination with poor nutrition and hygiene can lead to diarrhea, poor growth and increased mortality. While neomycin and zinc oxide can prevent post-weaning diarrhea (PWD), their broad-spectrum activity also kills commensal microbiota and can lead to the emergence of heavy metal and antimicrobial resistance. Bromelain prevents attachment of F4 ETEC to intestinal enterocytes by cleaving the host receptor. In controlled environmental facilities, weaned pigs treated with either therapeutic levels of neomycin sulfate, zinc oxide, bromelain or non-treated were monitored for diarrhea, weight gain, feed intake, feed efficiency, excretion of F4 ETEC, changes to their intestinal microbiomes and antimicrobial resistance in E. coli. The treatment effects were evaluated at weaning, during two weeks of treatment and for three weeks after treatments ceased. Minimal clinical signs of PWD were observed, except in zinc-treated pigs post treatment. Intestinal dysbiosis was observed in response to diarrhea and in pigs treated with both neomycin and zinc. Antimicrobial resistance increased in commensal E. coli isolated from neomycin- and zinc-treated pigs. In contrast, bromelain controlled PWD and prevented intestinal dysbiosis without inducing antimicrobial resistance.

Multi-Omics Analysis Reveals the Gut Microbiota Characteristics of Diarrheal Piglets Treated with Gentamicin

The involvement of alterations in gut microbiota composition due to the use of antibiotics has been widely observed. However, a clear picture of the influences of gentamicin, which is employed for the treatment of bacterial diarrhea in animal production, are largely unknown. Here, we addressed this problem using piglet models susceptible to enterotoxigenic Escherichia coli (ETEC) F4, which were treated with gentamicin. Gentamicin significantly alleviated diarrhea and intestinal injury. Through 16s RNS sequencing, it was found that gentamicin increased species richness but decreased community evenness. Additionally, clear clustering was observed between the gentamicin-treated group and the other groups. More importantly, with the establishment of a completely different microbial structure, a novel metabolite composition profile was formed. KEGG database annotation revealed that arachidonic acid metabolism and vancomycin resistance were the most significantly downregulated and upregulated pathways after gentamicin treatment, respectively. Meanwhile, we identified seven possible targets of gentamicin closely related to these two functional pathways through a comprehensive analysis. Taken together, these findings demonstrate that gentamicin therapy for diarrhea is associated with the downregulation of arachidonic acid metabolism. During this process, intestinal microbiota dysbiosis is induced, leading to increased levels of the vancomycin resistance pathway. An improved understanding of the roles of these processes will advance the conception and realization of new therapeutic and preventive strategies.

Complete association between CHCF1 genotype and enterotoxigenic Escherichia coli F4ab-associated post-weaning diarrhea in a pig challenge trial

Enterotoxigenic E. coli (ETEC) susceptibility in pigs is highly influenced by their genotype. The aim of this study was to determine the association between CHCF1 genotype and ETEC F4ab susceptibility in experimentally infected pigs. We investigated ETEC diarrhea development in CHCF1 heterozygous susceptible (RS) (n = 12 pigs) compared to CHCF1 homozygous resistant (RR) (n = 12 pigs) for six days after ETEC F4ab challenge. Afterwards, we genotyped with MUC4 and MUC13 markers to relate performance in identifying ETEC F4ab diarrhea susceptible pigs. In the CHCF1 RS group, 12/12 pigs developed ETEC diarrhea compared with 0/12 pigs in the CHCF1 RR group. Weight gain was lower in CHCF1 RS pigs compared with RR pigs (mean ± SD: 208 ± 323 g and 987 ± 615 g, p = 0.0007). Further, the shedding of hemolytic E. coli was significantly higher in CHCF1 RS pigs from 2 to 6 days post inoculation and they shed the challenge strain for more days (mean ± SD: 3.5 ± 1.6 days versus 0.5 ± 0.5 days, p < 0.0001). Twelve pigs with ETEC diarrhea were misclassified as resistant with the MUC4 marker and four pigs without ETEC diarrhea were misclassified as susceptible with the MUC13 marker. We found complete association between CHCF1 genotype and ETEC diarrhea development in pigs from a herd with Danbred genetics. The CHCF1 marker was more likely to determine the true host susceptibility to ETEC F4ab than the other markers. The marker shows potential for improving reliability of PWD challenge models and potentially for use in breeding for ETEC F4ab/ac resistance.

Microencapsulated probiotic Lactiplantibacillus plantarum and/or Pediococcus acidilactici strains ameliorate diarrhoea in piglets challenged with enterotoxigenic Escherichia coli

Lactiplantibacillus plantarum (strains 22F and 25F) and Pediococcus acidilactici (strain 72N) have displayed antibacterial activity in vitro, suggesting that they could be used to support intestinal health in pigs. The aim of this study was to determine if microencapsulated probiotics could reduce the severity of infection with enterotoxigenic Escherichia coli (ETEC) in weaned pigs. Sixty healthy neonatal piglets were cross-fostered and separated into five groups. Piglets to be given the microencapsulated probiotics received these orally on days 0, 3, 6, 9, and 12. Only piglets in groups 1 and 5 did not receive probiotics: those in groups 2 and 4 received the three microencapsulated probiotic strains (multi-strain probiotic), and piglets in group 3 received microencapsulated P. acidilactici strain 72N. After weaning, the pigs in groups 3-5 were challenged with 5 mL (at 10⁹ CFU/mL) of pathogenic ETEC strain L3.2 carrying the k88, staP, and stb virulence genes. The multi-strain probiotic enhanced the average daily gain (ADG) and feed conversion ratio (FCR) of weaned piglets after the ETEC challenge (group 4), whilst supplementing with the single-strain probiotic increased FCR (group 3). Piglets in groups 3 and 4 developed mild to moderate diarrhoea and fever. In the probiotic-fed piglets there was an increase in lactic acid bacteria count and a decrease in E. coli count in the faeces. By using real-time PCR, virulence genes were detected at lower levels in the faeces of pigs that had received the probiotic strains. Using the MILLIPLEX MAP assay, probiotic supplementation was shown to reduce pro-inflammatory cytokines (IL-1α, IL-6, IL-8, and TNFα), while group 4 had high levels of anti-inflammatory cytokine (IL-10). Challenged piglets receiving probiotics had milder intestinal lesions with better morphology, including greater villous heights and villous height per crypt depth ratios, than pigs just receiving ETEC. In conclusion, prophylactic administration of microencapsulated probiotic strains may improve outcomes in weaned pigs with colibacillosis.

Effect of chronic and acute enterotoxigenic E. coli challenge on growth performance, intestinal inflammation, microbiome, and metabolome of weaned piglets

Post-weaning enteropathies in swine caused by pathogenic E. coli, such as post-weaning diarrhea (PWD) or edema disease (ED), remain a significant problem for the swine industry. Reduction in the use of antibiotics over concerns of antibiotic resistance and public health concerns, necessitate the evaluation of effective antibiotic alternatives to prevent significant loss of livestock and/or reductions in swine growth performance. For this purpose, an appropriate piglet model of pathogenic E. coli enteropathy is required. In this study, we attempted to induce clinical signs of post-weaning disease in a piglet model using a one-time acute or lower daily chronic dose of a pathogenic E. coli strain containing genes for both heat stable and labile toxins, as well as Shiga toxin. The induced disease state was monitored by determining fecal shedding and colonization of the challenge strain, animal growth performance, cytokine levels, fecal calprotectin, histology, fecal metabolomics, and fecal microbiome shifts. The most informative analyses were colonization and shedding of the pathogen, serum cytokines, metabolomics, and targeted metagenomics to determine dysbiosis. Histopathological changes of the gastrointestinal (GI) tract and tight junction leakage as measured by fecal calprotectin concentrations were not observed. Chronic dosing was similar to the acute regimen suggesting that a high dose of pathogen, as used in many studies, may not be necessary. The piglet disease model presented here can be used to evaluate alternative PWD treatment options.

Impact of zinc oxide, benzoic acid and probiotics on the performance and cecal microbiota of piglets

Background

Intestinal health remains a key factor in animal production because it is essential for digestion, absorption and bacterial fermentation. Feed additives have been used to attenuate the weaning stress such as Zinc Oxide (ZnO) and benzoic acid (C₇H₆O₂). The objective of this study was to evaluate the impact of of benzoic acid and probiotics (BA + P) on performance, diarrhea and cecal microbiota of piglets in the nursery phase (23 to 65 days).

Results

One hundred and sixty weaned piglets with an initial weight of 6.335 ± 0.698 kg and 23 days of age were submitted to four treatments: supplementation with 2500 ppm of Zinc oxide (ZnO), supplementation with a commercial blend of benzoic acid and probiotics (Bacillus licheniformis, Bacillus subtilis and Enterococcus faecium NCIMB 10415; Vevogut P®) (BA + P), supplementation with Zinc oxide plus benzoic acid and probiotics (ZnO + BA + P), and controls receiving only the basal diet without any supplementation. At 65 days of age, 32 piglets (n = 8 per treatment) were slaughtered for the evaluation of the cecal microbiota. Supplementation with ZnO and BA + P were associated with better feed conversion (P < 0.05) in the early stage (23 to 49 days) and with an improvement in all performance parameters over the entire experimental period. The occurrence of diarrhea was lower (P < 0.05) in the BA + P group. The 4 most abundant phyla along with unclassified bacteria represented 93% of all sequences. Firmicutes dominated the cecal microbiota of all groups, followed by Bacteroidetes. Richness represented by the observed number of genera and by the Chao index were statistically lower in ZnO and ZnO + BA + P supplemented animals compared to controls. The beta diversity analysis that compares similarities between bacterial communities demonstrated formation of two distinct clusters containing samples with and without supplementation with ZnO, confirming a strong influence of ZnO on the intestinal microbiota.

Conclusion

The use of Benzoic acid with probiotics yields similar performance results with lower impact on the gut microbiota compared to ZnO, and it should be considered as a potential alternative in swine production.

Supplementary Information

The online version contains supplementary material available at 10.1186/s42523-021-00151-y.

Impact of Antibiotic Therapies on Resistance Genes Dynamic and Composition of the Animal Gut Microbiota

Antibiotics are major disruptors of the gastrointestinal microbiota, depleting bacterial species beneficial for the host health and favoring the emergence of potential pathogens. Furthermore, the intestine is a reactor of antibiotic resistance emergence, and the presence of antibiotics exacerbates the selection of resistant bacteria that can disseminate in the environment and propagate to further hosts. We reviewed studies analyzing the effect of antibiotics on the intestinal microbiota and antibiotic resistance conducted on animals, focusing on the main food-producing and companion animals. Irrespective of antibiotic classes and animal hosts, therapeutic dosage decreased species diversity and richness favoring the bloom of potential enteropathogens and the selection of antibiotic resistance. These negative effects of antibiotic therapies seem ineluctable but often were mitigated when an antibiotic was administered by parenteral route. Sub-therapeutic dosages caused the augmentation of taxa involved in sugar metabolism, suggesting a link with weight gain. This result should not be interpreted positively, considering that parallel information on antibiotic resistance selection was rarely reported and selection of antibiotic resistance is known to occur also at low antibiotic concentration. However, studies on the effect of antibiotics as growth promoters put the basis for understanding the gut microbiota composition and function in this situation. This knowledge could inspire alternative strategies to antibiotics, such as probiotics, for improving animal performance. This review encompasses the analysis of the main animal hosts and all antibiotic classes, and highlights the future challenges and gaps of knowledge that should be filled. Further studies are necessary for elucidating pharmacodynamics in animals in order to improve therapy duration, antibiotic dosages, and administration routes for mitigating negative effects of antibiotic therapies. Furthermore, this review highlights that studies on aminoglycosides are almost inexistent, and they should be increased, considering that aminoglycosides are the first most commonly used antibiotic family in companion animals. Harmonization of experimental procedures is necessary in this research field. In fact, current studies are based on different experimental set-up varying for antibiotic dosage, regimen, administration, and downstream microbiota analysis. In the future, shotgun metagenomics coupled with long-reads sequencing should become a standard experimental approach enabling to gather comprehensive knowledge on GIM in terms of composition and taxonomic functions, and of ARGs. Decorticating GIM in animals will unveil revolutionary strategies for medication and improvement of animals' health status, with positive consequences on global health.

Effects of Zinc Sources and Levels on Growth Performance, Zinc Status, Expressions of Zinc Transporters, and Zinc Bioavailability in Weaned Piglets

Simple Summary

Bioavailability of inorganic zinc in animals is low, and large amounts of zinc are excreted into feces, resulting in potential negative impacts on the environment and waste of zinc resources. To reduce zinc supplementation in animal feed, prepared and characterized chitosan–zinc (CS–Zn) chelate was studied to investigate its bioavailability. Dietary CS–Zn improved the weight gain of weaned piglets as compared to ZnSO₄. The Zn source had a significant influence on the liver, pancreas Zn contents, and the protein expression of ZnT1 and ZIP5 in duodenal mucosa. The Zn contents in the liver and pancreas and the protein expressions of ZnT1 and ZIP5 increased linearly with increases in the added Zn level. Multiple linear regression and the slope-ratio methodology showed that the bioavailability of CS–Zn was 110.9% or 149.0% relative to ZnSO₄, respectively, using zinc content in the liver or pancreas as the response parameter. These results indicate that CS–Zn shows enhanced bioavailability, suggesting a good potential substitute for inorganic zinc in animal nutrition.

Abstract

The present study was conducted to explore the bioavailability of chitosan–zinc chelate (CS–Zn) in weaned piglets, and its characteristics of prepared and oral safety were also involved. A total of 210 crossbred weaned piglets (Duroc × Landrace × Large White) with a mean body weight of 6.30 kg were randomly assigned into seven dietary treatments involving a 2 × 3 factorial arrangement with two Zn sources (CS–Zn and ZnSO₄) and three levels of added Zn (50, 100, 150 mg Zn/kg) plus a Zn-unsupplemented control diet. The feeding trial lasted 42 days. The AFM image of CS–Zn showed a rougher appearance and smaller size particles. The changes in spectrum peaks evidenced the successful chelating of Zn²⁺ with chitosan. The XRD patterns revealed the formation of a new crystalline phase. Moreover, the oral acute toxicity test of CS–Zn showed no lethal effects on mice. Weaned piglets fed dietary CS–Zn showed improved weight gain and decreased diarrhea incidence. Additionally, the bioavailability of CS–Zn was higher than that of ZnSO₄ in piglets. Taken together, these results indicate that the prepared CS–Zn chelate, with rough surface and crystalline phase, is non-toxic and show enhanced bioavailability.

Translational Approach to Induce and Evaluate Verocytotoxic E. coli O138 Based Disease in Piglets

Simple Summary

The aim of the study was to set up experimental conditions to simulate the simultaneous outbreak of post-weaning diarrhea and enterotoxaemia in weaned piglets, through verocytotoxic O138 Escherichia coli challenge. Zootechnical, clinical, microbiological, histological and immunological parameters were evaluated along the follow-up of control and infected groups. Results showed that experimental infection significantly affected the clinical status. Infected animals showed significant higher total median scores of epiphora, vitality, hair irregularity, oedema and depression; in addition, they displayed evident inflammatory infiltrate of lymphocytes, and follicular hyperplasia, increase of IgG in the intestinal crypts and CD3-positive T cells in intestinal epithelium. The infection model, carried out on receptor-mediated susceptible piglets, allowed to identify a discriminative panel of clinical symptoms related to Escherichia coli O138 infection and could be used to assess the protective effect of antibiotic alternatives.

Abstract

Pig livestock was influenced by several global concerns that imposed a re-thinking of the farming system, which included the reduction in chemical dependency and the development of antimicrobial alternatives. Post-weaning diarrhea and enterotoxaemia caused by Escherichia coli, are serious threats that are responsible for the economic losses related to mortality, morbidity and stunted growth in weaning piglets. The aim of the study was to set up experimental conditions to simulate the simultaneous outbreak of post-weaning diarrhea and enterotoxaemia in weaned piglets, through verocytotoxic O138 Escherichia coli challenge, with a multidisciplinary approach. Eighteen piglets susceptible to F18 VTEC infection were selected by polymerase chain reaction for polymorphism on the fucosyltransferase 1 gene and randomly divided in two experimental groups, non-infected controls (C; n = 6) and infected ones (I; n = 12) and housed into individual pens at the same environmental conditions for 29 days. At day 20, I pigs were orally inoculated with Escherichia coli O138 and fed a high protein ration for 3 days. Zootechnical, clinical, microbiological, histological and immunological parameters were evaluated along the follow up (3 and 9 days). Experimental infection, confirmed by bacteria faecal shedding of the I group, significantly affected the clinical status. The I group showed significantly higher total scores, corresponding to medians of the sum of daily scores from days 1 to 3 (Σ3) and 1 to 9 (Σ9) post infection, epiphora, vitality, hair irregularity, oedema and depression. Histological examination showed evident inflammatory infiltrate of lymphocytes, and follicular hyperplasia in I pigs; in the same group, the immunohistochemical and immunological assays revealed an increase in IgG in the intestinal crypts and CD3-positive T cells in intestinal epithelium. The experimental Escherichia coli infection in controlled conditions is crucial for both the evaluation of innovative compounds and the elucidation of the mechanisms associated with the persistence of antibacterial resistant strains. In conclusion, the adopted infection model, carried out on receptor-mediated susceptible piglets, allowed us to identify a discriminative panel of clinical symptoms related to Escherichia coli O138 infection, and could be used to assess the protective effect of antibiotic alternatives.

Use of Hydrolyzed Chinese Gallnut Tannic Acid in Weaned Piglets as an Alternative to Zinc Oxide: Overview on the Gut Microbiota

Simple Summary

The effects of dietary hydrolyzed Chinese gallnut tannic acid (GCT) as a replacement for ZnO were investigated on weaned piglets. A total of 72 piglets (31 ± 1 day) were selected and divided randomly into two groups: a control group, with a basal diet of + 1600 mg/kg ZnO; and a treated group, with a basal diet of + 1899.5 mg/kg GCT. The diarrhea rate of piglets in the treated group declined on days 14–21 than in the control group. Additionally, we found GCT can reduce the crypt depth of the ileum and improve antioxidant capacity. High throughput sequencing showed that the GCT increased the richness of bacteria (Lachnospiraceae, Prevotella, and Lactobacillus amylovorus) associated with the degradation of cellulose and hemicellulose. These data indicate that 1899.5 mg/kg GCT could be an alternative for 1600 mg/kg ZnO in the diet of piglets.

Abstract

The effects of dietary hydrolyzed Chinese gallnut tannic acid(GCT) as a replacement for ZnO were investigated on weaned piglets. A total of 72 weaned piglets at 31 ± 1 day (six replicate pens per treatment with six piglets per pen) were selected and divided randomly into two groups: a control group, with a basal diet of + 1600 mg/kg ZnO; and a treated group, with a basal diet of + 1899.5 mg/kg GCT. Data analysis showed that the significance of average daily gain and average daily feed intake between the two groups was p = 0.731 and p = 0.799, respectively. Compared with the control group, the diarrhea rate of piglets in the treated group underwent no noticeable change on days 0–7 (p = 0.383) and 7–14 (p = 0.263), but decreased significantly on days 14–21 (p < 0.05). Additionally, we found GCT can reduce the crypt depth of the ileum and improve its antioxidant capacity (p < 0.05). High throughput sequencing showed that GCT increased the richness of the bacteria Lachnospiraceae (p = 0.005), Prevotella_2 (p = 0.046) and Lactobacillus amylovorus (p = 0.081), which are associated with the degradation of cellulose and hemicellulose. The study indicated that 1899.5 mg/kg GCT could be an alternative for 1600 mg/kg ZnO in the diet of piglets.

Alginate oligosaccharide protects against enterotoxigenic Escherichia coli-induced porcine intestinal barrier injury

Alginate oligosaccharide (AOS) possesses various pharmaceutical benefits, making it an attractive candidate for biomedical applications. In the present study, we prepared AOS by depolymerising alginate; its degree of polymerisation mainly ranged from 2 to 8. We confirmed the enteroprotective potential of AOS against enterotoxigenic Escherichia coli (ETEC)-induced intestinal barrier injury in weaned pigs. Next, we illustrated the mechanisms underlying this effect of AOS using the porcine small intestinal epithelial cell line IPEC-J2. AOS potently reduced the binding of the bacteria-deprived endotoxin lipopolysaccharide (LPS) to the IPEC-J2 cell surface. Moreover, it suppressed the LPS-induced production of pro-inflammatory cytokines and the nuclear translocation of nuclear factor-κB (NF-κB) p65 in IPEC-J2 cells. These results indicate that AOS protects the intestinal epithelium from ETEC-induced inflammatory injury by preventing the activation of NF-κB, implying that AOS could be used as an anti-inflammatory agent for treating inflammation-related intestinal diseases in mammals.

Alternatives to antibiotics in a One Health context and the role genomics can play in reducing antimicrobial use

BACKGROUND

This review follows on from the International Conference on One Health Antimicrobial Resistance (ICOHAR 2019), where strategies to improve the fundamental understanding and management of antimicrobial resistance at the interface between humans, animals and the environment were discussed.

OBJECTIVE

This review identifies alternatives to antimicrobials in a One Health context, noting how advances in genomic technologies are assisting their development and enabling more targeted use of antimicrobials.

SOURCES

Key articles on the use of microbiota modulation, livestock breeding and gene editing, vaccination, antivirulence strategies and bacteriophage therapy are discussed.

CONTENT

Antimicrobials are central for disease control, but reducing their use is paramount as a result of the rise of transmissible antimicrobial resistance. This review discusses antimicrobial alternatives in the context of improved understanding of fundamental host-pathogen and microbiota interactions using genomic tools.

IMPLICATIONS

Host and microbial genomics and other novel technologies play an important role in devising disease control strategies for healthier animals and humans that in turn reduce our reliance on antimicrobials.

Cross-sectional study on rotavirus A (RVA) infection and assessment of risk factors in pre- and post-weaning piglets in India

Rotavirus A (RVA) infections are known to retard the piglets' growth and minimize the profit to the pig farming community. Between August 2014 and July 2017, in a cross-sectional study, we surveyed 13 organized pig farms located in the eight states of India representing northern, north-eastern and southern regions, to identify the risk factors associated with RVA infection in pre- and post-weaning piglets. Faecal samples (n = 411) comprising of non-diarrhoeic (n = 320) and diarrhoeic (n = 91) were collected and screened for RVA infection using VP6 gene-based RT-PCR. RVA positivity of 52.5% (168/320) in non-diarrhoeic and 59.3% (54/91) in diarrhoeic piglets was noticed. Further, 53.3% (120/225) and 54.8% (102/186) of the samples from pre- and post-weaned samples were positive for RVA, respectively. To note, no statistically significant association was noticed between RVA infection, health and weaning status. Additionally, a questionnaire-based survey was conducted to identify the risk factors for RVA infections in piglets. The analysis revealed that good ventilation (OR 0.2, 95% CI 0.15-0.39), use of deep well water (OR 0.2, 95% CI 0.13-0.43) and feeding of commercial feed (OR 0.3, 95% CI 0.18-0.41) were associated with reduced risk of RVA infection compared with poor ventilation, use of shallow well water and feeding of own milled feed, respectively. Contrarily, mixed farms (OR 2.1, 95% CI 1.26-3.37), use of heater or cooler (OR 5.9, 95% CI 3.74-9.30), sheds in different elevation (OR 2.5, 95% CI 1.20-5.01) and weekly and occasional use of disinfectant for surface cleaning (OR 1.8, 95% CI 1.12-2.96) were associated with higher RVA infection. Mitigating the risk factors might help in better health management of piglets and increase the economic return to pig farming community in the country.

A combination of yeast beta-glucan and milk hydrolysate is a suitable alternative to zinc oxide in the race to alleviate post-weaning diarrhoea in piglets

Zinc oxide (ZnO) is currently used as a dietary supplement to support gut homeostasis during the standard ‘abrupt’ weaning practices in commercial pig production. However, a replacement is urgently required as a ban on ZnO usage is imminent. The objective of this study was to explore the potential of a bovine casein hydrolysate (5kDaR) and yeast β-glucan, and their combination, as an alternative to ZnO. Eighty 21d old male piglets received a basal diet or supplemented with 5kDaR and yeast β-glucan alone or in combination, or ZnO from the day of weaning and were monitored for 10 days (n = 8/group; dietary groups: control diet; control diet + 5kDaR; control diet + yeast β-glucan; control diet + 5kDaR + yeast β-glucan; control diet + ZnO). Individually, supplement yeast β-glucan or 5kDaR did not improve gut health. In contrast, the yeast β-glucan + 5kDaR combination supplement supported a healthy gut, indicated by healthy faecal scores and improved growth parameters; similar to ZnO inclusion (P > 0.05). There was no negative effect on the gut microbiota with yeast β-glucan + 5kDaR supplementation; while ZnO negatively affected the Bifidobacterium spp. abundance (P < 0.05). The inflammatory NFκB pathway was suppressed by yeast β-glucan + 5kDaR supplementation, similar to ZnO (P > 0.05). In conclusion, the dietary supplement yeast β-glucan + 5kDaR restored homeostasis of the newly weaned piglet gut similar to the widely used ZnO, and can potentially replace ZnO.

In vitro synergy of sertraline and tetracycline cannot be reproduced in pigs orally challenged with a tetracycline resistant Escherichia coli

Background

Antimicrobial helper-compounds may reverse antimicrobial resistance. Sertraline, a antidepressant drug, has been suggested as a tetracycline helper-compound. Tetracycline is the preferred antimicrobial for treatment of enteric diseases in pigs. This study is the first to evaluate the potency of sertraline as a tetracycline adjuvant in pigs.

Methods

Forty-eight nursery pigs were divided into four treatment groups: Tetracycline, sertraline, tetracycline/sertraline or un-medicated control. Fecal and ileal samples were obtained before treatment, 48 h and nine days after five days of treatment, respectively. Colony forming units (CFU) of tetracycline resistant coliforms in each sample (ileal or fecal) and CFU of an orally inoculated tetracycline-resistant strain of Escherichia coli were determined at each sampling point. The microbiome of fecal and ileal and samples was analyzed by sequencing of the 16S V3-V4 region.

Results

The results did not provide evidence that sertraline in combination with tetracycline has any impact on tetracycline resistant bacteria in either fecal or ileum samples, while in the tetracycline treated group of pigs, an increase in the prevalence of a tetracycline resistant indicator strain of Escherichia coli shortly after ended five-day treatment was observed. The ileal samples obtained shortly after ended treatment showed treatment-associated changes in the composition of the microbiota in the groups of pigs treated with tetracycline (+/−) sertraline. While tetracycline treatment increased the abundance in the reads of E. coli, sertraline/tetracycline treatment led to increased abundances of Streptococcus spp. and decreased abundances of Lactobacillus spp. However, all observed differences (on CFU counts and microbiota composition) between groups shortly after treatment had diminished in less than two weeks after last treatment day.

Conclusions

Sertraline (+/−) tetracycline treatment did not reduce the long-term level of tetracycline-resistant bacteria in the feces or small intestine contents of piglets compared to the un-medicated control group of pigs. The result of this study reflects the importance of in vivo studies for confirmation of the antimicrobial helper-compound potential of an in vitro active compound.

Electronic supplementary material

The online version of this article (10.1186/s12866-018-1383-5) contains supplementary material, which is available to authorized users.

Risk factor analysis, antimicrobial resistance and pathotyping of Escherichia coli associated with pre- and post-weaning piglet diarrhoea in organised farms, India

A cross-sectional study was conducted from 2014 to 2017 in 13 organised pig farms located in eight states of India (Northern, North-Eastern and Southern regions) to identify the risk factors, pathotype and antimicrobial resistance of Escherichia coli associated with pre- and post-weaning piglet diarrhoea. The data collected through questionnaire survey were used to identify the risk factors by univariable analysis, in which weaning status, season, altitude, ventilation in the shed, use of heater/cooler for temperature control in the sheds, feed type, water source, and use of disinfectant, were the potential risk factors. In logistic regression model, weaning and source of water were the significant risk factors. The piglet diarrhoea prevalence was almost similar across the regions. Of the 909 faecal samples collected (North - 310, North-East - 194 and South - 405) for isolation of E. coli, pathotyping and antibiotic screening, 531 E. coli were isolated in MacConkey agar added with cefotaxime, where 345 isolates were extended spectrum β-lactamase (ESBL) producers and were positive for blaCTX-M-1 (n = 147), bla TEM (n = 151), qnrA (n = 98), qnrB (n = 116), qnrS (n = 53), tetA (n = 46), tetB (n = 48) and sul1 (n = 54) genes. Multiple antibiotic resistance (MAR) index revealed that 14 (2.64%) isolates had MAR index of 1. On the virulence screening of E. coli, 174 isolates harboured alone or combination of Stx1, Stx2, eaeA, hlyA genes. The isolates from diarrhoeic and post-weaning samples harboured higher number of virulence genes than non-diarrhoeic and pre-weaning. Alleviating the risk factors might reduce the piglet diarrhoea cases. The presence of multidrug-resistant and ESBL-producing pathogenic E. coli in piglets appears a public health concern.

Development of a pig infection model with colistin-resistant Escherichia coli

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mcr-1-positive ETEC and STEC strains persisted up to four weeks after inoculation.

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O149-F4 ETEC inoculation resulted in hyperthermia and moderate diarrhea.

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Fewer positive samples were obtained from pigs with the F4 resistant genotype.

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An mcr-1 gene transfer to other commensal isolates was observed for O139-F18 STEC.

Colistin-resistant Escherichia coli are isolated from pigs suffering from post-weaning diarrhea (PWD). This study was designed to develop an experimental model of PWD using mcr-1-carrying shiga toxin-producing E. coli (STEC) or enterotoxigenic E. coli (ETEC), for the future evaluation of control measures. Three groups of eight piglets, kept in high biosecurity units, were orally inoculated with mcr-1-positive STEC or ETEC, and one unchallenged group was used as a control. Clinical signs were recorded. Regularly-collected fecal samples and samples obtained from the digestive tract of animals sacrificed one month after inoculation were cultured in selective media and isolates were characterized. Blood samples were used to genotype the polymorphisms of the pigs’ intestinal receptors for F4 and F18 E. coli adhesins.

Diarrhea was more frequent and more fecal samples contained the inoculated strain in the group inoculated with the O149-F4 ETEC strain than with the O141-F18 or O139-F18 STEC strains. However, fewer positive samples were obtained from the two pigs with the F4 resistant genotype. The three inoculated strains could be re-isolated up to the end of the experiment. Excretion peaked on the first week after inoculation with the O149-F4 ETEC strain, and later for the other two. An mcr-1 gene transfer to other commensal isolates was observed only for O139-F18 STEC, while the loss of mcr-1 from the inoculated strain occurred in all groups. The O149-F4 ETEC challenge may be used to evaluate alternative solutions to combat PWD caused by colistin-resistant E. coli in pigs.

Effects of the lipid-coated zinc oxide dietary supplement on intestinal mucosal morphology and gene expression associated with the gut health in weanling pigs challenged with enterotoxigenic Escherichia coli K88

Effects of a lipid-coated zinc oxide (ZnO) Shield Zn® (SZ) vs. ZnO were evaluated. Forty 25-d-old weanling pigs were fed a nursery diet supplemented with 100 mg kg−1 Zn with ZnO (ZnO-100), ZnO-2500, SZ-100, -200, or -400. All piglets were challenged orally with 5 × 108 colony-forming units of enterotoxigenic Escherichia coli K88 on day 7 and euthanized on day 14. The fecal consistency score (FCS) was less for the SZ group vs. ZnO-100 (P < 0.05). The intestinal villus height:crypt depth ratio and goblet cell density were greater for the SZ group vs. ZnO-100. By regression analyses, SZ-100 to -200 and SZ-300 to -400 were comparable to ZnO-2500 in the FCS and intestinal variables, respectively. The jejunal mucosal mRNA level did not differ between the SZ group and either ZnO group in insulin-like growth factor-I and multiple structural proteins and cytokines including zonula occludens protein (ZO) 1 and interleukin (IL) 10 except for lower ZO-1 and IL-10 mRNA levels for the SZ group than for ZnO-2500 and ZnO-100, respectively. The ZO-1 mRNA level regressed positively on the supplemental SZ concentration. Results suggest that SZ play a role in epithelial barrier function and inflammation by modulating the expression of ZO-1 and IL-10.

Protein fermentation in the gut; implications for intestinal dysfunction in humans, pigs, and poultry

The amount of dietary protein is associated with intestinal disease in different vertebrate species. In humans, this is exemplified by the association between high-protein intake and fermentation metabolite concentrations in patients with inflammatory bowel disease. In production animals, dietary protein intake is associated with postweaning diarrhea in piglets and with the occurrence of wet litter in poultry. The underlying mechanisms by which dietary protein contributes to intestinal problems remain largely unknown. Fermentation of undigested protein in the hindgut results in formation of fermentation products including short-chain fatty acids, branched-chain fatty acids, ammonia, phenolic and indolic compounds, biogenic amines, hydrogen sulfide, and nitric oxide. Here, we review the mechanisms by which these metabolites may cause intestinal disease. Studies addressing how different metabolites induce epithelial damage rely mainly on cell culture studies and occasionally on mice or rat models. Often, contrasting results were reported. The direct relevance of such studies for human, pig, and poultry gut health is therefore questionable and does not suffice for the development of interventions to improve gut health. We discuss a roadmap to improve our understanding of gut metabolites and microbial species associated with intestinal health in humans and production animals and to determine whether these metabolite/bacterial networks cause epithelial damage. The outcomes of these studies will dictate proof-of-principle studies to eliminate specific metabolites and or bacterial strains and will provide the basis for interventions aiming to improve gut health.

Hydrolysable chestnut tannins for reduction of postweaning diarrhea: Efficacy on an experimental ETEC F4 model

An experimental model for postweaning diarrhea with enterotoxigenic Escherichia coli F4 (ETEC F4) was set up in piglets, and the efficacy of 1% chestnut-tannin extract in preventing diarrhea was subsequently assessed. In a first trial (infection model), 32 Swiss Large White piglets (age: 24 days; average BW: 7.8 ± 0.8 kg) were randomly assigned to two experimental groups (infected [INF], noninfected [NINF]). In a subsequent trial, 72 Swiss Large White piglets (age: 26 days; average BW: 7.4 ± 1.5 kg) were blocked by BW and assigned within block to four experimental groups: NINF-CO: not infected and fed a standard control starter diet (CO); INF-CO: infected and fed the CO diet; NINF-TA: not infected and fed the CO diet supplemented with 1% chestnut extract containing 54% of hydrolysable tannins (TA); and INF-TA: infected and fed the TA diet. Both diets (TA and CO) were formulated to be isocaloric and isoproteic and to meet or surpass the nutritional requirements. In both trials, four days after weaning, piglets assigned to the INF group received an oral suspension of ETEC F4. Fecal score, ETEC shedding in feces (only in trial 2), and growth performance traits were measured for the following 14 days post infection. In both trials, more than 50% of the INF piglets developed diarrhea within six days post infection. Tannins reduced (P < 0.05) the average fecal score, the percentage of piglets in diarrhea, and the duration of diarrhea, whereas feed intake and the average daily gain were unaffected.

Effect of chicken egg anti-F4 antibodies on performance and diarrhea incidences in enterotoxigenic Escherichia coli K88+-challenged piglets

The aim was to evaluate the effects of dietary supplementation of spay-dried whole egg containing anti-F4 antibodies (SDWE) against recombinantly produced F4 antigens in enterotoxigenic Escherichia coli K88⁺ (ETEC)-challenged piglets. Twenty-seven 21-d-old and individually housed piglets were randomly allotted to 3 treatments consisting of a wheat-soybean meal basal diet containing either 0 (control egg powder; CEP), 0.1% (SDWE1) or 0.4% (SDWE2) SDWE. After a 7-d adaptation period, blood samples were collected from all pigs, and pigs were weighed and orally challenged with an ETEC inoculum. Blood was sampled at 24 and 48 h post-challenge, and diarrhea incidences and scores were recorded. On d 14, all pigs were weighed and then euthanized to obtain intestinal tissue samples for histomorphology measurement. During the pre-challenge period, pigs fed the SDWE showed a linear improvement (P < 0.05) in average daily gain (ADG) and gain to feed ratio (G:F), but there were no differences among treatments in growth performance during the post-challenge period. Diarrhea incidences and scores, fecal shedding of ETEC, plasma urea nitrogen content and intestinal histomorphology were similar among treatments. The results show that 0.4% SDWE supported greater piglet performance before challenge although such benefits were not evident during the post-challenge period at either 0.1% or 0.4% supplementation.

Intestinal absorption differences of major bioactive compounds of Gegenqinlian Decoction between normal and bacterial diarrheal mini-pigs in vitro and in situ

Intestinal condition plays an important role in drug absorption and metabolism, thus the effects of varied gastrointestinal diseases such as infectious diarrhea on the intestinal function are crucial for drug absorption. However, due to the lack of suitable models, the differences of absorption and metabolism of drugs between the diarrheal and normal intestines are rarely reported. Thus, in this study, Escherichia coli diarrhea model was induced in mini-pigs and single-pass intestinal perfusion and intestinal mucosal enzyme metabolism experiments were conducted. A simple and rapid ultrahigh performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method was developed to determine the concentrations of 9 major components in Gegen Qinlian decoction (GQD). Samples were pretreated by protein precipitation with methanol and naringin and prednisolone were used as internal standards. The validated method demonstrated adequate sensitivity, selectivity, and process efficiency for the bioanalysis of 9 compounds. Results of intestinal perfusion showed that puerarin, daidzein, daidzin and baicalin and berberine were absorbed faster in diarrheal jejunum than in normal intestines (p < 0.05). However, puerarin, daidzin and liquiritin were metabolized more slowly in diarrheal intestine after incubation compared with the normal group (p < 0.05). The concentrations of daidzein in both perfusion and metabolism and wogonin in metabolism were significantly increased (p < 0.05). In conclusion, absorption and metabolism of GQD were significantly different between the diarrheal and normal intestines, which suggest that bacterial diarrheal mini-pigs model can be used in the intestinal absorption study and is worthy to be applied in the other intestinal absorption study of anti- diarrheal drugs.

Induction of experimental sub-clinical post-weaning colibacillosis in pigs

Newly weaned pigs are at least partially protected against sub-clinical gastrointestinal disorders through the provision of in-feed antimicrobials. Possible associations with antibiotic resistance to life threatening bacterial infections in humans and environmental pollution will result in their ban. As a consequence, gut health and pig performance will be compromised. Current research is aimed at reducing, and eventually overcoming, such consequences through novel nutritional strategies. Effects of the latter on the consequences of sub-clinical infection may be assessed in an infection model, since the absence of in-feed antimicrobials does not always lead to gastrointestinal disorders, due to e.g. variation in infectious environmental conditions. A common gastrointestinal disorder is post-weaning colibacillosis (PWC), which is caused by enterotoxigenic E. coli (ETEC), and is associated with diarrhoea and reduced food intake, and hence reduced performance. Existing ETEC infection models, which have yielded variable results and employed relatively large infective doses of ETEC, have focused on clinical PWC (Madec et al., 2000). The objective of our experiment was to assess whether sub-clinical PWC can be induced through experimental infection with ETEC, and whether such sub-clinical PWC is sensitive to the level of infection used.

Combined effects of chitosan and microencapsulated Enterococcus faecalis CG1.0007 probiotic supplementation on performance and diarrhea incidences in enterotoxigenic Escherichia coli K88+ challenged piglets

The aim of this study was to investigate the combined effects of chitosan oligosaccharide (COS) and a microencapsulated Enterococcus faecalis CG1.0007 probiotic (PRO) on growth performance and diarrhea incidences in enterotoxigenic Escherichia coli (ETEC) K88⁺ challenged piglets in a 14-d study. Thirty piglets, 7.19 ± 0.52 kg initial BW weaned at 21 ± 1 d, were allotted to 5 treatment groups (n = 6) consisting of a corn-soybean meal diet with no additive (negative control, NC), NC + 0.25% chlortetracycline (positive control, PC), NC + 400 mg/kg COS (COS), NC + 100 mg/kg PRO (PRO) and NC + a combination of COS and PRO (CPRO). Pigs were individually housed in cages, acclimated to treatments for a 7-d period and had ad libitum access to feed and water throughout the study. On d 8, pigs were weighed, blood samples were collected, and then orally challenged with 6 mL (1 × 10¹¹ cfu/mL) of freshly grown ETEC inoculum. During post-challenge period, blood was sampled at 24 and 48 h to determine plasma urea nitrogen (PUN), and diarrhea incidences and fecal consistency scores were recorded from d 9 to 12. On d 14, all pigs were weighed and then euthanized to obtain intestinal tissue samples for histomorphometric measurements. Growth performance responses were similar among treatments during the pre- and post-challenge periods. There were no significant differences in PUN content, incidences of diarrhea, and fecal consistency scores among treatments. The intestinal histomorphology results did not differ significantly among treatments except for PC with increased (P = 0.0001) villus:crypt ratio compared with the NC. Under the conditions of the present study, it can be concluded that supplementation of piglet diets with 400 mg/kg COS, 100 mg/kg microencapsulated PRO or their combination did not significantly improve piglet growth performance both during the pre- and post-ETEC K88⁺ oral inoculation. Also, there were no significant reduction of incidences and severity of diarrhea after challenge compared with the control group.

Comparison of porous and nano zinc oxide for replacing high-dose dietary regular zinc oxide in weaning piglets

The aim of this study was to compare the effect of dietary supplementation with low dose of porous and nano zinc oxide (ZnO) on weaning piglets, and to evaluate the possibility of using them as an alternative to high dose of regular ZnO. Piglets were randomly allocated into four treatment groups fed with four diets: (1) basal diet (NC), (2) NC+ 3000 mg/kg ZnO (PC), (3) NC + 500 mg/kg porous ZnO (HiZ) and (4) NC + 500 mg/kg nano ZnO (ZNP). The result showed that piglets in HiZ group had less diarrhea than ZNP group (P < 0.05). Besides, there was no significant difference between PC, HiZ and ZNP groups in terms of serum malondialdeyhde (MDA) concentration and glutathione peroxidase (GSH-Px) activity (P > 0.05). Analysis of trace metal elements revealed that piglets fed with high dose of regular ZnO had the highest Zn level in kidney (P < 0.05), which may induce kidney stone formation. Additionally, a decrease in ileal crypt depth was observed in PC, HiZ and ZNP group, suggesting an effective protection against intestinal injury. Results of mRNA analysis in intestine showed that ZNP supplementation had better effects on up-regulated trefoil factor 3 (TFF3) and nuclear factor erythroid 2-related factor 2 (Nrf2) levels in duodenum and jejunum than HiZ did (P < 0.05), implying that nano ZnO may possess higher anti-inflammatory capacity than porous ZnO. In conclusion, dietary supplementation with low dose of porous and nano ZnO had similar (even better) effect on improving growth performance and intestinal morphology, reducing diarrhea and intestinal inflammatory as high dose of regular ZnO in weaning piglets. Compared with nano ZnO, porous ZnO had better performance on reducing diarrhea but less effect on up-regulation of intestinal TFF3 and Nrf2.

Post weaning diarrhea in pigs: risk factors and non-colistin-based control strategies

Post-weaning diarrhea (PWD) is one of the most serious threats for the swine industry worldwide. It is commonly associated with the proliferation of enterotoxigenic Escherichia coli in the pig intestine. Colistin, a cationic antibiotic, is widely used in swine for the oral treatment of intestinal infections caused by E. coli, and particularly of PWD. However, despite the effectiveness of this antibiotic in the treatment of PWD, several studies have reported high rates of colistin resistant E. coli in swine. Furthermore, this antibiotic is considered of very high importance in humans, being used for the treatment of infections due to multidrug-resistant (MDR) Gram-negative bacteria (GNB). Moreover, the recent discovery of the mcr-1 gene encoding for colistin resistance in Enterobacteriaceae on a conjugative stable plasmid has raised great concern about the possible loss of colistin effectiveness for the treatment of MDR-GNB in humans. Consequently, it has been proposed that the use of colistin in animal production should be considered as a last resort treatment only. Thus, to overcome the economic losses, which would result from the restriction of use of colistin, especially for prophylactic purposes in PWD control, we believe that an understanding of the factors contributing to the development of this disease and the putting in place of practical alternative strategies for the control of PWD in swine is crucial. Such alternatives should improve animal gut health and reduce economic losses in pigs without promoting bacterial resistance. The present review begins with an overview of risk factors of PWD and an update of colistin use in PWD control worldwide in terms of quantities and microbiological outcomes. Subsequently, alternative strategies to the use of colistin for the control of this disease are described and discussed. Finally, a practical approach for the control of PWD in its various phases is proposed.

Interactive effect of dietary protein and dried citrus pulp levels on growth performance, small intestinal morphology, and hindgut fermentation of weanling pigs

Weanling pigs ( = 108, 21 d of age, 5.82 ± 0.16 kg initial BW) were assigned to a 2 × 2 factorial arrangement of treatments to evaluate the effects of dietary levels of CP (high- and low-CP diets) and dried citrus pulp (DCP; 0% and 7.5%) on growth performance, small intestinal morphology, and hindgut fermentation. Pigs were blocked by initial BW and allotted to 1 of 9 pens, each containing 3 pigs. The high-CP diets consisted of feeding 20% and 21% CP levels throughout phase 1 (0 to 14 d) and phase 2 (14 to 28 d), respectively. For the low-CP diets, CP levels were reduced by 4% units as compared with the high-CP diets in both phases. Crystalline AA were supplied to maintain an ideal AA pattern. Pig BW and pen feed disappearance were recorded weekly. On d 7 and 28 postweaning, 1 pig from each pen was euthanized for collection of small intestinal tissues and digesta from cecum and colon. There were no CP × DCP interactions for growth performance and gut morphology. Although the low-CP diet decreased ADG ( = 0.03) and G:F ( = 0.02) from d 21 to 28 postweaning, overall performance was unaffected by the treatments. On d 7 postweaning, pigs fed the low-CP diet tended to have increased ( = 0.09) crypt depth in the duodenum. Low-CP diets tended to increase ( = 0.06) crypt depth and reduce ( = 0.08) villus:crypt ratio in the jejunum on d 7. Dietary treatments did not affect ileal morphology. On d 7 postweaning, low-CP diets tended to reduce ( = 0.09) cecal total VFA, whereas dietary DCP inclusion tended to decrease ( = 0.07) colonic propionate. Including 7.5% DCP to the diet decreased ( < 0.05) colonic isovalerate and ammonia N concentrations on d 7 only for pigs fed the low-CP diet. On d 28 postweaning, DCP inclusion in low-CP diets decreased ( < 0.05) butyrate, isovalerate, and valerate concentrations in the cecum, as well as isovalerate, valerate, and ammonia N concentrations in the colon. Including 7.5% DCP to the diet increased ( < 0.05) acetate:propionate ratio in the hindgut on both d 7 and 28 postweaning only for pigs fed the high-CP diet. Lactate concentration was unaffected by the treatments. These results indicate that feeding low-CP AA-supplemented diets did not compromise overall growth performance, but slightly increased damage in the gut morphology of weanling pigs. Moreover, adding 7.5% DCP to low-CP AA-supplemented diets shifted the fermentation pattern in the hindgut of weanling pigs by decreasing protein fermentation metabolites.

Effects of Ex Vivo Infection with ETEC on Jejunal Barrier Properties and Cytokine Expression in Probiotic-Supplemented Pigs

BACKGROUND AND AIM

Enterotoxigenic Escherichia coli (ETEC) strains are involved in piglet post-weaning diarrhea. Prophylactic measures including probiotics have been examined in infection experiments with live piglets. In the present study, we have tested whether the early effects of ETEC infection can also be evoked and studied in a model in which ETEC is added to whole mucosal tissues ex vivo, and whether this response can be modulated by prior supplementation of the piglets with probiotics.

METHODS

Jejunal barrier and transport properties of Enterococcus faecium-supplemented or control piglets were assessed in Ussing chambers. Part of the epithelia was challenged with an ETEC strain at the mucosal side. Fluxes of fluorescein as a marker of paracellular permeability, and the expression of selected tight junction (TJ) proteins and of proinflammatory cytokines were measured.

RESULTS

The addition of ETEC ex vivo induced an increase in transepithelial resistance peaking in the first 2 h with a concomitant reduction in fluorescein fluxes, indicating tightening effects on barrier function. The response of short-circuit current after stimulation with PGE₂ or glucose was reduced in epithelia treated with ETEC. ETEC induced a decrease in the TJ protein claudin-4 in the control diet group after 280 min and an increase in the mRNA expression of the proinflammatory cytokines interleukin-8 and TNF-α in both groups after 180 min.

CONCLUSIONS

The addition of ETEC ex vivo affected barrier function and transport properties of the jejunal tissues and enhanced cytokine expression. The differences in claudin-4 expression in the jejunum might indicate a beneficial effect of E. faecium prefeeding.

Characterisation of Early-Life Fecal Microbiota in Susceptible and Healthy Pigs to Post-Weaning Diarrhoea

Early-life microbial exposure is of particular importance to growth, immune system development and long-lasting health. Hence, early microbiota composition is a promising predictive biomarker for health and disease but still remains poorly characterized in regards to susceptibility to diarrhoea. In the present study, we aimed to assess if gut bacterial community diversity and composition during the suckling period were associated with differences in susceptibility of pigs to post-weaning diarrhoea. Twenty piglets from 5 sows (4 piglets / litter) were weaned in poor housing conditions to challenge their susceptibility to post-weaning diarrhoea. Two weeks after weaning, 13 pigs exhibited liquid faeces during 2 or 3 days and were defined as diarrhoeic (D) pigs. The other 7 pigs did not have diarrhea during the whole post-weaning experimental periodand were defined as healthy (H) pigs. Using a molecular characterisation of fecal microbiota with CE-SSCP fingerprint, Next Generation Sequencing and qPCR, we show that D and H pigs were mainly discriminated as early as postnatal day (PND) 7, i.e. 4 weeks before post-weaning diarrhoea occurence. At PND 7 H pigs displayed a lower evenness and a higher abundance of Prevotellaceae, Lachnospiraceae, Ruminocacaceae and Lactobacillaceae compared to D pigs. The sPLS regression method indicates that these bacterial families were strongly correlated to a higher Bacteroidetes abundance observed in PND 30 H pigs one week before diarrhoea. These results emphasize the potential of early microbiota diversity and composition as being an indicator of susceptibility to post-weaning diarrhoea. Furthermore, they support the health promoting strategies of pig herds through gut microbiota engineering.

Pigs experimentally infected with an enterotoxigenic strain of Escherichia coli have improved feed efficiency and indicators of inflammation with dietary supplementation of tryptophan and methionine in the immediate post-weaning period

This experiment tested the hypothesis that pigs challenged with an enterotoxigenic strain of E. coli (ETEC) will improve performance by dietary supplementation of sulfur amino acids (SAA) and tryptophan (Trp) above the current recommended levels in the immediate post-weaning period. Male pigs (n = 96) weighing 6.2 ± 0.78 kg (mean ± s.d.) and weaned at 21 days were stratified into one of four treatments based on weaning weight (n = 24). Four diets were formulated [11.2 MJ NE/kg; 20.1% crude protein, 1.25% standardised ileal digestible (SID) lysine (Lys)] according to a 2 × 2 factorial arrangement of treatments with two levels of SID SAA : Lys ratio (0.52 vs 0.60) and two levels of SID Trp : Lys ratio (0.16 vs 0.24). Diets did not contain any antimicrobial compounds. Pigs were individually housed and were fed diets for 14 days after weaning. Pigs were infected with ETEC (3.44 × 108 CFU/mL, serotype O149 : K91 : K88) on Days 5, 6, and 7 after weaning. Pigs were bled on Days 5, 8 and 14 and subsequently analysed for plasma levels of acute-phase proteins, urea, cytokines (Days 5 and 8 only) and amino acids (Days 5 and 8 only). Increasing Trp (P = 0.036) and SAA (P = 0.028) improved feed conversion ratio, and combined supplementation of SAA and Trp further improved FCR than individual supplementation of either SAA or Trp (P = 0.092). Dietary treatments had no impact on the incidence of post-weaning diarrhoea (P > 0.05). Increasing SAA increased shedding of ETEC on Days 12 and 14 after weaning (P < 0.019). Increasing dietary Trp reduced the intensity of inflammation (as measured by APP Index = [(C-reactive protein × PigMAP)/apolipoprotein A1]) immediately after infection with ETEC (P < 0.05), while increasing dietary SAA reduced the APP index on 24 h and 7 days after ETEC infection (P < 0.05). Increasing dietary SAA reduced plasma levels of interferon-gamma regardless of dietary Trp or day of sampling (P = 0.043). Increasing dietary SAA decreased plasma urea (PU) levels on Days 5, 8 and 14 (P < 0.05). These data indicate that Trp supplementation reduced the intensity of inflammation and SAA supplementation decreased the pro-inflammatory interferon-gamma response and improved protein utilisation, as measured by PU, whereas supplementation with both Trp and SAA improved feed conversion ratio.

New perspectives to the enterotoxigenic E. coli F4 porcine infection model: Susceptibility genotypes in relation to performance, diarrhoea and bacterial shedding

Enterotoxigenic E. coli (ETEC), causing post-weaning diarrhoea, is a major problem in weaned piglets. Individual animal responses to ETEC infection show high variability in animal experiments. Two studies were designed to optimize the ETEC F4ac infection model in piglets by combining the genotype susceptibility with performance, diarrhoea incidence and bacterial shedding. The studies were performed with respectively 120 and 80 male piglets that were tested for susceptibility or resistance towards ETEC O149:F4ac by a DNA marker based test. Three different genotypes were observed; resistant (RR), susceptible heterozygote (RS) and susceptible homozygote (SS). Piglets, were orally infected with an inoculum suspension (containing 1.5E8 CFU/ml ETEC F4ac) at day 0, 1 and 2 of the study. Performance, diarrhoea incidence and bacterial shedding were followed for 21days. In the first week after challenge a difference in average daily gain was observed between resistant and susceptible piglets in both studies. For the complete study period no significant differences were observed. Diarrhoea incidence was significantly higher in susceptible pigs compared to the resistant pigs in the first week after challenge. Bacterial shedding was much higher in the susceptible pigs and ETEC excretion lasted longer. ETEC was hardly detected in the faecal material of the resistant pigs. In conclusion, susceptible pigs showed higher diarrhoea incidence and higher numbers of faecal ETEC shedding in the first week after challenge compared to resistant pigs. The DNA marker based test can be used to select pigs that are susceptible for ETEC for inclusion in ETEC infection model, resulting in less animals needed to perform infection studies.

Prevalence of adhesin and toxin genes in E. coli strains isolated from diarrheic and non-diarrheic pigs from smallholder herds in northern and eastern Uganda

Background

Enterotoxigenic E. coli (ETEC) significantly contribute to diarrhea in piglets and weaners. The smallholder pig producers in Uganda identified diarrhea as one of the major problems especially in piglets. The aim of this study was to; i) characterize the virulence factors of E. coli strains isolated from diarrheic and non-diarrheic suckling piglets and weaners from smallholder herds in northern and eastern Uganda and ii) identify and describe the post-mortem picture of ETEC infection in severely diarrheic piglets. Rectal swab samples were collected from 83 piglets and weaners in 20 herds and isolated E. coli were characterized by PCR, serotyping and hemolysis.

Results

The E. coli strains carried genes for the heat stable toxins STa, STb and EAST1 and adhesins F4 and AIDA-I. The genes for the heat labile toxin LT and adhesins F5, F6, F18 and F41 were not detected in any of the E. coli isolates. Where the serogroup could be identified, E. coli isolates from the same diarrheic pig belonged to the same serogroup. The prevalence of EAST1, STb, Stx2e, STa, AIDA-I, and F4 in the E. coli isolates from suckling piglets and weaners (diarrheic and non-diarrheic combined) was 29, 26.5, 2.4, 1.2, 16, and 8.4 %, respectively. However the prevalence of F4 and AIDA-I in E. coli from diarrheic suckling piglets alone was 22.2 and 20 %, respectively. There was no significant difference in the prevalence of the individual virulence factors in E. coli from the diarrheic and non-diarrheic pigs (p > 0.05). The main ETEC strains isolated from diarrheic and non-diarrheic pigs included F4/STb/EAST1 (7.2 %), F4/STb (1.2 %), AIDA/STb/EAST1 (8 %) and AIDA/STb (8 %). At post-mortem, two diarrheic suckling piglets carrying ETEC showed intact intestinal villi, enterocytes and brush border but with a layer of cells attached to the brush border, suggestive of ETEC infections.

Conclusion

This study has shown that the F4 fimbriae is the most predominant in E. coli from diarrheic piglets in the study area and therefore an F4-based vaccine should be considered one of the preventive measures for controlling ETEC infections in the piglets in northern and eastern Uganda.

Electronic supplementary material

The online version of this article (doi:10.1186/s12866-016-0796-2) contains supplementary material, which is available to authorized users.

Marine macroalgal extracts to maintain gut homeostasis in the weaning piglet

The mammalian gastrointestinal tract (GIT) is a dynamic environment, where a symbiotic relationship exists between the resident microbiota and the digestive and immune systems of the host. The development of the immune system begins in-utero and is further developed after the colonization of the GIT with microbiota during birth and postnatal life. The early establishment of this relationship is fundamental to the development and long-term maintenance of gut homeostasis. Regulatory mechanisms ensure an appropriate level of immune reactivity in the gut to accommodate the presence of beneficial and dietary microorganisms, whereas allowing effective immune responses to clear pathogens. However, unfavorable alterations in the composition of the microbiota, known as dysbiosis, have been implicated in many conditions including post-weaning diarrhea in pigs. Weaning is a major critical period in pig husbandry. It involves complex dietary, social, and environmental stresses that interfere with gut development. Post-weaning complications in piglets are characterized by a reduction in-feed intake and growth, atrophy of small intestine architecture, upregulation of intestinal inflammatory cytokines, alterations in GIT microflora, diarrhea, and heightened susceptibility to infection. These challenges have been controlled with in-feed prophylactic antibiotics and dietary minerals. However, these strategies are under scrutiny because of their role in promoting multidrug resistant bacteria and the accumulation of minerals in the environment, respectively. Therefore, significant efforts are being made to identify natural alternatives to support homeostasis in the piglet GIT, in particular during the weaning period. Chemodiversity in nature; including microorganisms, terrestrial plants, seaweeds, and marine organisms, offers a valuable source for novel bioactives. In this review, we discuss the advances in our understanding of the immune mechanisms by which the dynamic interplay of the intestinal microbiota and its host normally favors a homeostatic, symbiotic relationship, and how feeding macroalgal bioactives in both the maternal diet and the piglet diet, can be used to support this symbiotic relationship in times of challenge.

Effects of a lipid-encapsulated zinc oxide dietary supplement, on growth parameters and intestinal morphology in weanling pigs artificially infected with enterotoxigenic Escherichia coli

The study was performed to investigate the effect of dietary supplementation of a lipid-encapsulated Zinc oxide on growth parameters and intestinal mucosal morphology piglets born to Duroc-sired Landrace × Yorkshire dams. Twenty-four 30-day-old piglets weaned at 25 days of age were orally challenged with 5 × 10(8) colony forming units of enterotoxigenic Escherichia coli (ETEC) K88 and fed one of the four diets for 7 days: (i) a nursery basal diet containing 100-ppm ZnO (referred to as BASAL), (ii) BASAL supplemented with 120-ppm apramycin (referred to as ANTIBIO), (iii) BASAL with 2,400-ppm ZnO (referred to as HIGH), and BASAL containing 100-ppm lipid-encapsulated ZnO (referred to as LE). All piglets were killed at the end of the experiment for histological examination on the intestine. The results showed that the average daily gain (ADG), the villus height: crypt depth (CD) ratio in the ileum, and the goblet cell density of the villus and crypt in the duodenum, jejunum, and colon were greater in the LE-fed group that those of the BASAL (p < 0.05). Fecal consistency score (FCS) and the CD ratio in the ileum were less in the LE-fed group, compared to the BASAL-fed one (p < 0.05). The effects observed in the LE-fed group were almost equal to those of the HIGH-fed group as well as even superior to those of the ANTIBIO-fed group. Taken together, our results imply that dietary supplementation of 100-ppm lipid-encapsulated ZnO is as effective as that of 2,400-ppm ZnO for promoting growth diarrhea and intestinal morphology caused by ETEC infection.

Effect of maternal supplementation with seaweed extracts on growth performance and aspects of gastrointestinal health of newly weaned piglets after challenge with enterotoxigenic Escherichia coli K88

In the present study, a 2 × 2 factorial arrangement was conducted to investigate the effect of maternal supplementation with seaweed extracts ( - SWE v. +SWE, n 20) from day 83 of gestation until weaning (day 28) on post-weaning (PW) growth performance, faecal score, faecal enterotoxigenic Escherichia coli (ETEC) toxin quantification, intestinal histology and cytokine mRNA of unchallenged and ETEC-challenged pigs. Pigs were ETEC challenged on day 9 PW. There was a maternal treatment × challenge (SWE × ETEC) interaction effect on growth performance and faecal score (P< 0.05). Pigs from SWE-supplemented sows and ETEC-challenged (SE) had higher average daily gain (ADG) during 0-13 d PW and reduced faecal score during 0-72 h post-challenge than those from basal-fed sows and ETEC-challenged (BE) (P< 0.05). However, there was no difference between unchallenged pigs from the SWE-supplemented sows (SC) and basal-fed sows (BC) (P>0.10). Pigs from the SWE-supplemented sows had reduced heat-labile enterotoxin gene copy numbers than those from the basal-fed sows (P< 0.05). Maternal SWE supplementation increased the villus height in the ileum of pigs (P< 0.05). There was a SWE × ETEC interaction effect (P< 0.05) on IL-6 mRNA and a SWE × gastrointestinal (GI) region interaction effect (P< 0.05) on transforming growth factor-β1 (TGF-β1) and TNF-α mRNA. IL-6 mRNA was down-regulated in SC pigs than BC pigs (P< 0.05). However, there was no difference in IL-6 mRNA between SE and BE pigs. The mRNA of TGF-β1 and TNF-α was down-regulated in the colon of pigs from the SWE-supplemented sows compared with those from the basal-fed sows (P< 0.05). However, there was no difference in TGF-β1 and TNF-α mRNA in the ileum between the pigs from the SWE-supplemented sows and basal-fed sows. In conclusion, maternal SWE supplementation improves ADG and the aspects of GI health of weaned pigs following an ETEC challenge.

Effects of dietary supplementation of lipid-encapsulated zinc oxide on colibacillosis, growth and intestinal morphology in weaned piglets challenged with enterotoxigenic Escherichia coli

This study was aimed to evaluate the effect of dietary supplementation of lipid-encapsulated (coated) zinc oxide ZnO on post-weaning diarrhea (colibacillosis) in weaned piglets challenged with enterotoxigenic Escherichia coli (ETEC). Thirty-two 35-day-old weaned piglets were orally challenged with 3 × 10(10) colony forming units of ETEC K88 while eight piglets received no challenge (control). Each eight challenged piglets received a diet containing 100 ppm ZnO (low ZnO), 2500 ppm ZnO (high ZnO) or 100 ppm of lipid (10%)-coated ZnO (coated ZnO) for 7 days; control pigs received the low ZnO diet. Daily gain, goblet cell density in the villi of the duodenum, jejunum and ileum, and villus height in the jejunum and ileum, which decreased due to the challenge, were equally greater in the coated ZnO and high ZnO groups versus low ZnO group. Fecal consistency score, serum interleukin-8 concentration, subjective score of fecal E. coli shedding, and digesta pH in the stomach, jejunum and ileum, which increased due to the challenge, were equally low in the coated ZnO and high ZnO groups versus low ZnO. Results suggest that a low level of coated ZnO might well substitute for a pharmacological level of native ZnO in dietary supplementation to alleviate colibacillosis of weaned piglets.

Protective effect of oral administration of transgenic tobacco seeds against verocytotoxic Escherichia coli strain in piglets

The use of transgenic plants as delivery system for antigenic proteins is attractive for its simplicity and increases likelihood for local immune response at sites of infection. The aim of this study was to evaluate the protective effect of oral administration of tobacco seeds, expressing the FedA, the major protein of the F18 adhesive fimbriae, and B subunit of verocytotoxin, against verocytotoxin-producing E. coli (VTEC) strain in piglets. Forty-three early weaned piglets, were randomly divided into 4 experimental groups: 3 test groups and a control. Treatment groups orally received a bolus, with different dose of tobacco seeds on 0, 1, 2, 14 days post primary administration. After challenge, with 1*10(10) CFU of O138 Escherichia coli strain, piglets showed clinical scores significantly higher in the control group compared to orally immunized groups (P < 0.05) and the latter showed a faster recovery than in CG. In conclusion, oral administration of recombinant tobacco seeds expressing antigenic proteins against VTEC strains can induce a protective effect against challenger strain in piglets.

Chitosan-zinc chelate improves intestinal structure and mucosal function and decreases apoptosis in ileal mucosal epithelial cells in weaned pigs

The present study was conducted to investigate the effects of chitosan (CS)-Zn on intestinal morphology, mucosal epithelial cell apoptosis and mucosal immune function in weanling pigs. A total of 150 weanling barrows with a body weight of 7.2 kg were randomly allocated into five groups. A basal diet without Zn supplementation was used as the control and other four groups were fed the control diet supplemented with 50 or 100 mg/kg of Zn as CS-Zn, 100 mg/kg of Zn as ZnSO4 and 3000 mg/kg of Zn as ZnO, respectively. The feeding trial lasted for 28 d. The results showed that serum diamine oxidase activities, d-lactate levels and endotoxin contents were lower in pigs fed dietary 100 mg/kg of Zn as CS-Zn or 3000 mg/kg of Zn as ZnO than in pigs fed the control or 100 mg Zn/kg as ZnSO4 diet. The ratios of the villus height:crypt depth of the duodenum, jejunum and ileum were higher in pigs that received 100 mg/kg of Zn as CS-Zn or a high level of Zn as ZnO than in pigs fed the control diet. Moreover, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end labelling (TUNEL)-stained ileal epithelial cells were found in the control group, and apoptotic cells did not appear prominently in pigs that received the 100 mg/kg of CS-Zn or ZnO diet. Secretory IgA concentration in ileal mucus was increased in the dietary group that received 100 mg/kg of CS-Zn or ZnO. These results indicated that dietary 100 mg CS-Zn/kg had similar biological effects to dietary 3000 mg ZnO/kg on intestinal morphology, mucosal epithelial cell apoptosis and mucosal immune function.

Changes in gut microbial populations, intestinal morphology, expression of tight junction proteins, and cytokine production between two pig breeds after challenge with Escherichia coli K88: a comparative study

This study hypothesized that the gut microbial populations, intestinal morphology, and cytokine production are differentially altered in 2 different pig breeds, namely, Chinese native Jinhua pigs and European Landrace pigs, after orally challenge with enterotoxigenic Escherichia coli (ETEC) K88. A total of 12 Jinhua pigs and 12 Landrace pigs were allocated to either the nonchallenged or the challenged groups (6 pigs per group). The challenged pigs were orally administered ETEC K88, and their nonchallenged counterparts were given sterile Luria-Bertani broth. Selected gut microbial populations, intestinal morphology, mRNA expression of tight junction proteins, and the levels of ileal cytokines and secretory immunoglobulin A (sIgA) production were measured in Jinhua and Landrace pigs. The results showed that the challenged Jinhua pigs exhibited a significantly (P < 0.05) lower incidence of diarrhea compared with their Landrace counterparts. The Escherichia coli (E.coli) population and the percentage of E. coli in the total bacteria population were increased in response to ETEC K88 challenge in both Jinhua and Landrace pigs. The challenged Landrace pigs shed more E. coli (P < 0.05) and had higher percentage of E. coli in the total bacteria population in the colon (P < 0.05) compared with their Jinhua counterparts. Both pig breeds tended to exhibit greater villous atrophy and crypt depth reduction in all of the intestinal segments with challenge. The expression of tight junction proteins decreased in response to ETEC K88 challenge in both pig breeds. The levels of the proinflammatory cytokines interferon (IFN)-γ, tumor necrosis factor-α, and IL-6 and the secretion of sIgA were positively altered whereas the levels of the anti-inflammatory cytokine IL-4 and transforming growth factor (TGF)-β were negatively altered by ETEC K88 challenge in both breeds. Jinhua pigs exhibited significantly higher levels of IFN-γ and TGF-β (P < 0.05) in the challenged group. Our findings provide valuable evidence to explain the differences in the intestinal physiology between Jinhua and Landrace pigs; that is, Jinhua pigs appeared to show better growth performance, a lower incidence of diarrhea, and a lower extent of immune activation in response to ETEC K88 challenge and a higher Lactobacillus population, a higher percentage of Lactobacillus in the total bacteria population, a higher ratio of Lactobacillus to E. coli, and higher levels of tight junction proteins with and without challenge.

Dietary addition of Lactobacillus rhamnosus GG impairs the health of Escherichia coli F4-challenged piglets

Lactobacillus rhamnosus GG (LGG) is a probiotic for humans and is normally not found in pigs; however, it has been shown to protect the human-derived intestinal Caco-2 cells against the damage induced by an important intestinal pathogen, enterotoxigenic Escherichia coli F4 (ETEC). An experiment was conducted to test whether the dietary addition of LGG improves the growth and health of weaned pigs when orally challenged by E. coli F4. Thirty-six pigs were weaned at 21 days and assigned to a standard weaning diet with or without 1010 CFU LGG (ATCC 53103) per day. The pigs, individually penned, were orally challenged with 1.5 ml of a 1010 CFU E. coli F4 suspension on day 7 and slaughtered on day 12 or 14. With the addition of LGG, the average daily gain and the average daily feed intake were reduced after the challenge with ETEC and for the entire trial (P < 0.05). The average faecal score tended to worsen from day 11 to the end of the trial and the concentration of ETEC in the faeces tended to increase (P = 0.07) with the LGG supplementation. The counts of lactic acid bacteria, enterobacteria and yeasts in the colonic digesta were not affected. The pH values in ileal, colonic and caecal digesta, and the small intestine size were also unchanged. Regardless of the site of measurement (duodenum, jejunum or ileum), a trend of decreased villus height was seen with LGG (P = 0.10). Crypt depth and villus to crypt ratio were unchanged by the diet. A gradual increase of total seric IgA was seen after 1 week and after the challenge, in the control (P < 0.05), but not in the treated group. After the challenge, the LGG reduced the total IgA in the blood serum (P < 0.05), v. the control. The total IgA in the saliva and in the jejunum secretion were not affected by the diet. The F4-specific IgA activity was not affected by the diet at all the samplings. Our result shows that, the administration of LGG do not prevent or reduce the detrimental effect of the E. coli F4 infection on the growth performance and health status of weaned piglet.

Casein modified gold nanoparticles for future theranostic applications

The synthesis and characterization of gold nanoparticles (AuNPs 20 nm sized) modified with k-casein derived peptides in order to monitor the peptide effect as bacterial adhesion inhibitor, thanks to the carrier/concentrator effect of the AuNPs is here presented. Some aspects related to the stability of AuNP/peptide conjugates for a potential application in the design of an electrochemical biosensor for pathogen bacteria detection are also discussed. This peptide based nanoparticle assay takes advantage of the dual character of the AuNPs: as carrier of the biorecognition molecule and also as electrocatalytic label, allowing the evaluation of the pathogen bacteria-peptide interaction in a simple and rapid way through the chronoamperometric monitoring of the hydrogen evolution reaction on screen-printed carbon electrodes. The developed proof of concept theranostic system may open the way to therapeutic and biosensing applications with interest for various fields.

Gastrointestinal health and function in weaned pigs: a review of feeding strategies to control post-weaning diarrhoea without using in-feed antimicrobial compounds

For the last several decades, antimicrobial compounds have been used to promote piglet growth at weaning through the prevention of subclinical and clinical disease. There are, however, increasing concerns in relation to the development of antibiotic-resistant bacterial strains and the potential of these and associated resistance genes to impact on human health. As a consequence, European Union (EU) banned the use of antibiotics as growth promoters in swine and livestock production on 1 January 2006. Furthermore, minerals such as zinc (Zn) and copper (Cu) are not feasible alternatives/replacements to antibiotics because their excretion is a possible threat to the environment. Consequently, there is a need to develop feeding programs to serve as a means for controlling problems associated with the weaning transition without using antimicrobial compounds. This review, therefore, is focused on some of nutritional strategies that are known to improve structure and function of gastrointestinal tract and (or) promote post-weaning growth with special emphasis on probiotics, prebiotics, organic acids, trace minerals and dietary protein source and level.