Succession, Replacement, and Modification of Chicken Litter Microbiota.

Chickens are in constant interaction with their environment, e.g., bedding and litter, and their microbiota. However, how litter microbiota develops over time and whether bedding and litter microbiota may affect the cecal microbiota is not clear. We addressed these questions using sequencing of V3/V4 variable region of 16S rRNA genes of cecal, bedding, and litter samples from broiler breeder chicken flocks for 4 months of production. Cecal, bedding, and litter samples were populated by microbiota of distinct composition. The microbiota in the bedding material did not expand in the litter. Similarly, major species from litter microbiota did not expand in the cecum. Only cecal microbiota was found in the litter forming approximately 20% of total litter microbiota. A time-dependent development of litter microbiota was observed. Escherichia coli, Staphylococcus saprophyticus, and Weissella jogaejeotgali were characteristic of fresh litter during the first month of production. Corynebacterium casei, Lactobacillus gasseri, and Lactobacillus salivarius dominated in a 2-month-old litter, Brevibacterium, Brachybacterium, and Sphingobacterium were characteristic for 3-month-old litter, and Salinococcus, Dietzia, Yaniella, and Staphylococcus lentus were common in a 4-month-old litter. Although the development was likely determined by physicochemical conditions in the litter, it might be interesting to test some of these species for active modification of litter to improve the chicken environment and welfare. IMPORTANCE Despite intimate contact, the composition of bedding, litter, and cecal microbiota differs considerably. Species characteristic for litter microbiota at different time points of chicken production were identified thus opening the possibility for active manipulation of litter microbiota.

Ecological Adaptations of Gut Microbiota Members and Their Consequences for Use as a New Generation of Probiotics.

In this review, we link ecological adaptations of different gut microbiota members with their potential for use as a new generation of probiotics. Gut microbiota members differ in their adaptations to survival in aerobic environments. Interestingly, there is an inverse relationship between aerobic survival and abundance or potential for prolonged colonization of the intestinal tract. Facultative anaerobes, aerotolerant Lactobacilli and endospore-forming Firmicutes exhibit high fluctuation, and if such bacteria are to be used as probiotics, they must be continuously administered to mimic their permanent supply from the environment. On the other hand, species not expressing any form of aerobic resistance, such as those from phylum Bacteroidetes, commonly represent host-adapted microbiota members characterized by vertical transmission from mothers to offspring, capable of long-term colonization following a single dose administration. To achieve maximal probiotic efficacy, the mode of their administration should thus reflect their natural ecology.

Whole genome sequencing and function prediction of 133 gut anaerobes isolated from chicken caecum in pure cultures.

BACKGROUND: In order to start to understand the function of individual members of gut microbiota, we cultured, sequenced and analysed bacterial anaerobes from chicken caecum. RESULTS: Altogether 204 isolates from chicken caecum were obtained in pure cultures using Wilkins-Chalgren anaerobe agar and anaerobic growth conditions. Genomes of all the isolates were determined using the NextSeq platform and subjected to bioinformatic analysis. Among 204 sequenced isolates we identified 133 different strains belonging to seven different phyla - Firmicutes, Bacteroidetes, Actinobacteria, Proteobacteria, Verrucomicrobia, Elusimicrobia and Synergistetes. Genome sizes ranged from 1.51 Mb in Elusimicrobium minutum to 6.70 Mb in Bacteroides ovatus. Clustering based on the presence of protein coding genes showed that isolates from phyla Proteobacteria, Verrucomicrobia, Elusimicrobia and Synergistetes did not cluster with the remaining isolates. Firmicutes split into families Lactobacillaceae, Enterococcaceae, Veillonellaceae and order Clostridiales from which the Clostridium perfringens isolates formed a distinct sub-cluster. All Bacteroidetes isolates formed a separate cluster showing similar genetic composition in all isolates but distinct from the rest of the gut anaerobes. The majority of Actinobacteria clustered closely together except for the representatives of genus Gordonibacter showing that the genome of this genus differs from the rest of Actinobacteria sequenced in this study. Representatives of Bacteroidetes commonly encoded proteins (collagenase, hemagglutinin, hemolysin, hyaluronidase, heparinases, chondroitinase, mucin-desulfating sulfatase or glutamate decarboxylase) that may enable them to interact with their host. Aerotolerance was recorded in Akkermansia and Cloacibacillus and was also common among representatives of Bacteroidetes. On the other hand, Elusimicrobium and the majority of Clostridiales were highly sensitive to air exposure despite their potential for spore formation. CONCLUSIONS: Major gut microbiota members utilise different strategies for gut colonisation. High oxygen sensitivity of Firmicutes may explain their commonly reported decrease after oxidative burst during gut inflammation.

Complete sequence of multidrug resistance p9134 plasmid and its variants including natural recombinant with the virulence plasmid of Salmonella serovar Typhimurium.

In this study we determined the complete nucleotide sequence of multidrug-resistance plasmid p9134, and its variants p9134dT and p9134dAT which spontaneously lost either tetracycline or both tetracycline and ampicillin resistance, respectively. The plasmids were 133,802 bp, 109,512 bp and 127,291 bp in size, respectively, and their basic backbone was similar to that of IncI plasmids. Genes coding for ampicillin (blaTEM), chloramphenicol (catA1), streptomycin (strA, strB), tetracycline (tetA(A)) and gentamicin (aac(3)-IV) resistance were confirmed in wild-type p9134. Moreover, a gene for hygromycine resistance (hph) and a putative gene for apramycin resistance were newly determined. In p9134dAT, a continuous sequence coding for ampicillin and tetracycline resistances was lost. Genetic rearrangements in p9134dT were more complex and 2 recombination events must have occurred. During the first one, the tetracycline resistance locus was replaced with rck, srgB, srgA, orf7 and pefI originating from Salmonella virulence plasmid pSLT. During the second one, ydjA, pifA and repC genes from p9134 were replaced with repA2, PSLT025 and PSLT026 genes from pSLT. Our findings indicate that recombination event between unrelated plasmids might be quite common and may lead to the generation and selection of plasmids both transferring antibiotic resistance and increasing virulence of their host.

Comparative Genome Analysis and Characterization of the Probiotic Properties of Lactic Acid Bacteria Isolated from the Gastrointestinal Tract of Wild Boars in the Czech Republic.

Probiotics are crucial components for maintaining a healthy gut microbiota in pigs, especially during the weaning period. Lactic acid bacteria (LAB) derived from the gastrointestinal tract of wild boars can serve as an abundant source of beneficial probiotic strains with suitable properties for use in pig husbandry. In this study, we analyzed and characterized 15 strains of Limosilactobacillus mucosae obtained from the gut contents of wild boars to assess their safety and suitability as probiotic candidates. The strains were compared using pan-genomic analysis with 49 L. mucosae strains obtained from the NCBI database. All isolated strains demonstrated their safety by showing an absence of transferrable antimicrobial resistance genes and hemolysin activity. Based on the presence of beneficial genes, five candidates with probiotic properties were selected and subjected to phenotypic profiling. These five selected isolates exhibited the ability to survive conditions mimicking passage through the host's digestive tract, such as low pH and the presence of bile salts. Furthermore, five selected strains demonstrated the presence of corresponding carbohydrate-active enzymes and the ability to utilize various carbohydrate substrates. These strains can enhance the digestibility of oligosaccharide or polysaccharide substrates found in food or feed, specifically resistant starch, α-galactosides, cellobiose, gentiobiose, and arabinoxylans. Based on the results obtained, the L. mucosae isolates tested in this study appear to be promising candidates for use as probiotics in pigs.

Antibiotic Susceptibility, Resistance Gene Determinants and Corresponding Genomic Regions in Lactobacillus amylovorus Isolates Derived from Wild Boars and Domestic Pigs.

Restrictions on the use of antibiotics in pigs lead to the continuous search for new probiotics serving as an alternative to antibiotics. One of the key parameters for probiotic bacteria selection is the absence of horizontally transmissible resistance genes. The aim of our study was to determine antibiotic susceptibility profiles in 28 Lactobacillus amylovorus isolates derived from the digestive tract of wild boars and farm pigs by means of the broth microdilution method and whole genome sequencing (WGS). We revealed genetic resistance determinants and examined sequences flanking resistance genes in these strains. Our findings indicate that L. amylovorus strains from domestic pigs are predominantly resistant to tetracycline, erythromycin and ampicillin. WGS analysis of horizontally transmissible genes revealed only three genetic determinants (tetW, ermB and aadE) of which all tetW and ermB genes were present only in strains derived from domestic pigs. Sequence analysis of coding sequences (CDS) in the neighborhood of the tetW gene revealed the presence of site-specific recombinase (xerC/D), site-specific DNA recombinase (spoIVCA) or DNA-binding transcriptional regulator (xre), usually directly downstream of the tetW gene. In the case of ermB, CDS for omega transcriptional repressor or mobilization protein were detected upstream of the ermB gene.

Probiotic Lactobacilli Do Not Protect Chickens against Salmonella Enteritidis Infection by Competitive Exclusion in the Intestinal Tract but in Feed, Outside the Chicken Host.

Lactobacilli are commonly used as probiotics in poultry to improve production parameters and to increase chicken resistance to enteric infections. However, lactobacilli do not efficiently colonise the chicken intestinal tract, and also, their anti-infection effect in vivo is sometimes questionable. In this study, we therefore evaluated the potential of a mixture of four Lactobacillus species (L. salivarius, L. reuteri, L. ingluviei and L. alvi) for the protection of chickens against Salmonella Enteritidis infection. Whenever the chickens were inoculated by lactobacilli and S. Enteritidis separately, there was no protective effect of lactobacilli. This means that when lactobacilli and S. Enteritidis are exposed to each other as late as in the crop of chickens, lactobacilli did not influence chicken resistance to S. Enteritidis at all. The only positive effect was recorded when the mixture of lactobacilli and S. Enteritidis was used for the inoculation of feed and the feed was anaerobically fermented for 1 to 5 days. In this case, chickens fed such a diet remained S. Enteritidis negative. In vitro experiments showed that the protective effect was caused by acidification of feed down to pH 4.6 due to lactobacilli fermentation and was associated with S. Enteritidis inactivation. The probiotic effect of lactobacilli was thus expressed in the feed, outside the chicken host.

Host Species Adaptation of Obligate Gut Anaerobes Is Dependent on Their Environmental Survival.

The gut microbiota of warm-blooded vertebrates consists of bacterial species belonging to two main phyla; Firmicutes and Bacteroidetes. However, does it mean that the same bacterial species are found in humans and chickens? Here we show that the ability to survive in an aerobic environment is central for host species adaptation. Known bacterial species commonly found in humans, pigs, chickens and Antarctic gentoo penguins are those capable of extended survival under aerobic conditions, i.e., either spore-forming, aerotolerant or facultatively anaerobic bacteria. Such bacteria are ubiquitously distributed in the environment, which acts as the source of infection with similar probability in humans, pigs, chickens, penguins and likely any other warm-blooded omnivorous hosts. On the other hand, gut anaerobes with no specific adaptation for survival in an aerobic environment exhibit host adaptation. This is associated with their vertical transmission from mothers to offspring and long-term colonisation after administration of a single dose. This knowledge influences the design of next-generation probiotics. The origin of aerotolerant or spore-forming probiotic strains may not be that important. On the other hand, if Bacteroidetes and other host-adapted species are used as future probiotics, host preference should be considered.

The distribution of antibiotic resistance genes in chicken gut microbiota commensals.

Antibiotic resistance in bacterial pathogens or several indicator bacteria is commonly studied but the extent of antibiotic resistance in bacterial commensals colonising the intestinal tract is essentially unknown. In this study, we aimed to investigate the presence of horizontally acquired antibiotic resistance genes among chicken gut microbiota members in 259 isolates with known whole genomic sequences. Altogether 124 isolates contained at least one gene coding for antibiotic resistance. Genes coding for the resistance to tetracyclines (detected in 101 isolates), macrolide-lincosamide-streptogramin B antibiotics (28 isolates) and aminoglycosides (25 isolates) were the most common. The most frequent tetracycline resistance genes were tet(W), tet(32), tet(O) and tet(Q). Lachnospiraceae and Ruminococcaceae frequently encoded tet(W). Lachnospiraceae commonly coded also for tet(32) and tet(O). The tet(44) gene was associated with Erysipelotrichaceae and tet(Q) was detected in the genomes of Bacteroidaceae and Porphyromonadaceae. Without any bias we have shown that antibiotic resistance is quite common in gut commensals. However, a comparison of codon usage showed that the above-mentioned families represent the most common current reservoirs but probably not the original host of the detected resistances.

Eggshell and Feed Microbiota Do Not Represent Major Sources of Gut Anaerobes for Chickens in Commercial Production.

In this study, we addressed the origin of chicken gut microbiota in commercial production by a comparison of eggshell and feed microbiota with caecal microbiota of 7-day-old chickens, using microbiota analysis by 16S rRNA sequencing. In addition, we tested at which timepoint during prenatal or neonatal development it is possible to successfully administer probiotics. We found that eggshell microbiota was a combination of environmental and adult hen gut microbiota but was completely different from caecal microbiota of 7-day-old chicks. Similarly, we observed that the composition of feed microbiota was different from caecal microbiota. Neither eggshell nor feed acted as an important source of gut microbiota for the chickens in commercial production. Following the experimental administration of potential probiotics, we found that chickens can be colonised only when already hatched and active. Spraying of eggs with gut anaerobes during egg incubation or hatching itself did not result in effective chicken colonisation. Such conclusions should be considered when selecting and administering probiotics to chickens in hatcheries. Eggshells, feed or drinking water do not act as major sources of gut microbiota. Newly hatched chickens must be colonised from additional sources, such as air dust with spores of Clostridiales. The natural colonisation starts only when chickens are already hatched, as spraying of eggs or even chickens at the very beginning of the hatching process did not result in efficient colonisation.

Environmental Impact on Differential Composition of Gut Microbiota in Indoor Chickens in Commercial Production and Outdoor, Backyard Chickens.

In this study, we compared the caecal microbiota composition of egg-laying hens from commercial production that are kept indoors throughout their whole life with microbiota of hens kept outdoors. The microbiota of outdoor hens consisted of lower numbers of bacterial species than the microbiota of indoor hens. At the phylum level, microbiota of outdoor hens was enriched for Bacteroidetes (62.41 ± 4.47% of total microbiota in outdoor hens and 52.01 ± 6.27% in indoor hens) and Proteobacteria (9.33 ± 4.99% in outdoor and 5.47 ± 2.24% in indoor hens). On the other hand, Firmicutes were more abundant in the microbiota of indoor hens (33.28 ± 5.11% in indoor and 20.66 ± 4.41% in outdoor hens). Horizontally transferrable antibiotic resistance genes tetO, tet(32), tet(44), and tetW were also less abundant in the microbiota of outdoor hens than indoor hens. A comparison of the microbiota composition at the genus and species levels pointed toward isolates specifically adapted to the two extreme environments. However, genera and species recorded as being similarly abundant in the microbiota of indoor and outdoor hens are equally as noteworthy because these represent microbiota members that are highly adapted to chickens, irrespective of their genetics, feed composition, and living environment.

Different Bacteroides Species Colonise Human and Chicken Intestinal Tract.

Bacteroidaceae are common gut microbiota members in all warm-blooded animals. However, if Bacteroidaceae are to be used as probiotics, the species selected for different hosts should reflect the natural distribution. In this study, we therefore evaluated host adaptation of bacterial species belonging to the family Bacteroidaceae. B. dorei, B. uniformis, B. xylanisolvens, B. ovatus, B. clarus, B. thetaiotaomicron and B. vulgatus represented human-adapted species while B. gallinaceum, B. caecigallinarum, B. mediterraneensis, B. caecicola, M. massiliensis, B. plebeius and B. coprocola were commonly detected in chicken but not human gut microbiota. There were 29 genes which were present in all human-adapted Bacteroides but absent from the genomes of all chicken isolates, and these included genes required for the pentose cycle and glutamate or histidine metabolism. These genes were expressed during an in vitro competitive assay, in which human-adapted Bacteroides species overgrew the chicken-adapted isolates. Not a single gene specific for the chicken-adapted species was found. Instead, chicken-adapted species exhibited signs of frequent horizontal gene transfer, of KUP, linA and sugE genes in particular. The differences in host adaptation should be considered when the new generation of probiotics for humans or chickens is designed.

Gut microbiota composition before infection determines the Salmonella super- and low-shedder phenotypes in chicken.

Heterogeneity of infection and extreme shedding patterns are common features of animal infectious diseases. Individual hosts that are super-shedders are key targets for control strategies. Nevertheless, the mechanisms associated with the emergence of super-shedders remain largely unknown. During chicken salmonellosis, a high heterogeneity of infection is observed when animal-to-animal cross-contaminations and reinfections are reduced. We hypothesized that unlike super-shedders, low-shedders would be able to block the first Salmonella colonization thanks to a different gut microbiota. The present study demonstrates that (i) axenic and antibiotic-treated chicks are more prone to become super-shedders; (ii) super or low-shedder phenotypes can be acquired through microbiota transfer; (iii) specific gut microbiota taxonomic features determine whether the chicks develop a low- and super-shedder phenotype after Salmonella infection in isolator; (iv) partial protection can be conferred by inoculation of four commensal bacteria prior to Salmonella infection. This study demonstrates the key role plays by gut microbiota composition in the heterogeneity of infection and pave the way for developing predictive biomarkers and protective probiotics.

Use of 16S rRNA gene sequencing for prediction of new opportunistic pathogens in chicken ileal and cecal microbiota.

In this study, we addressed differences in the development of gut microbiota in 4 successive batches of commercially hatched broiler parent chickens. When planning this study, we expected to find a batch with compromised performance which would allow identification of microbiota of suboptimal composition. Microbiota composition was determined only by sequencing the V3/V4 region of 16S rRNA genes in samples collected from chickens 5 to 18 wk of age. In a total, 100 and 160 samples originating from the ileum or cecum were processed, respectively. In one of the flocks with suboptimal performance we identified an increased abundance of Helicobacter brantae forming over 80% of ileal microbiota in individual chickens. Moreover, we also tested samples of 53-wk-old hens from the same genetic line in which egg production decreased. In this case, cecal microbiota was enriched for Fusobacterium mortiferum forming over 30% of total cecal microbiota. Although none of the identified unusual microbiota members have been well recognized as pathogenic, they may represent new opportunistic pathogens of chickens worth of further investigation. Analysis of gut microbiota composition by next generation sequencing thus proved as a useful and unbiased alternative to bacterial culture, especially in the cases of unspecific symptoms like decrease in flock performance.

Systematic Culturomics Shows that Half of Chicken Caecal Microbiota Members can be Grown in Vitro Except for Two Lineages of Clostridiales and a Single Lineage of Bacteroidetes.

Epidemiological data show that the composition of gut microbiota influences host health, disease status, and even behaviour. However, to confirm these epidemiological observations in controlled experiments, pure cultures of gut anaerobes must be obtained. Since the culture of gut anaerobes is not a simple task due to the large number of bacterial species colonising the intestinal tract, in this study we inoculated 174 different culture media with caecal content from adult hens, and compared the microbiota composition in the original caecal samples and in bacterial masses growing in vitro by 16S rRNA sequencing. In total, 42% of gut microbiota members could be grown in vitro and since there were some species which were not cultured but for which the culture conditions are known, it is likely that more than half of chicken gut microbiota can be grown in vitro. However, there were two lineages of Clostridiales and a single lineage of Bacteroidetes which were common in chicken caecal microbiota but resistant to culture. Of the most selective culture conditions, nutrient broths supplemented with mono- or di-saccharides, including those present in fruits, positively selected for Lactobacillaceae. The addition of bile salts selected for Veillonellaceae and YCFA (yeast casitone fatty acid agar) enriched for Desulfovibrionaceae. In addition, Erysipelotrichaceae were positively selected by colistin, trimethoprim, streptomycin and nalidixic acid. Culture conditions tested in this study can be used for the selective enrichment of desired bacterial species but also point towards the specific functions of individual gut microbiota members.

Gut Anaerobes Capable of Chicken Caecum Colonisation.

Chicks in commercial production are highly sensitive to enteric infections and their resistance can be increased by administration of complex adult microbiota. However, it is not known which adult microbiota members are capable of colonising the caecum of newly hatched chicks. In this study, we therefore orally inoculated chicks with pure cultures of 76 different bacterial isolates originating from chicken caecum on day 1 of life and determined their ability to colonise seven days later. The caecum of newly hatched chickens could be colonised by bacteria belonging to phyla Bacteroidetes, Proteobacteria, Synergistetes, or Verrucomicrobia, and isolates from class Negativicutes (phylum Firmicutes). On the other hand, we did not record colonisation with isolates from phyla Actinobacteria and Firmicutes (except for Negativicutes), including isolates from families Lachnospiraceae, Ruminococcaceae, Erysipelotrichaceae, and Lactobacillaceae. Representatives of genera commonly used in probiotics such as Lactobacillus, Enterococcus, or Bacillus therefore did not colonise the chicken intestinal tract after a single dose administration. Following challenge with Salmonella enterica serovar Enteritidis, the best protecting isolates increased the chicken's resistance to S. Enteritidis only tenfold, which, however, means that none of the tested individual bacterial isolates on their own efficiently protected chicks against S. Enteritidis.

Contact with adult hen affects development of caecal microbiota in newly hatched chicks.

Chickens in commercial production are hatched in a clean hatchery environment in the absence of any contact with adult hens. However, Gallus gallus evolved to be hatched in a nest in contact with an adult hen which may act as a donor of gut microbiota. In this study, we therefore addressed the issue of microbiota development in newly hatched chickens with or without contact with an adult hen. We found that a mere 24-hour-long contact between a hen and newly hatched chickens was long enough for transfer of hen gut microbiota to chickens. Hens were efficient donors of Bacteroidetes and Actinobacteria. However, except for genus Faecalibacterium and bacterial species belonging to class Negativicutes, hens did not act as an important source of Gram-positive Firmicutes. Though common to the chicken intestinal tract, Lactobacilli and isolates from families Erysipelotrichaceae, Lachnospiraceae and Ruminococcaceae therefore originated from environmental sources instead of from the hens. These observation may have considerable consequences for the evidence-based design of the new generation of probiotics for poultry.

Infectious bursal disease virus infection leads to changes in the gut associated-lymphoid tissue and the microbiota composition.

Infectious bursal disease (IBD) is an acute, highly contagious and immunosuppressive poultry disease. IBD virus (IBDV) is the causative agent, which may lead to high morbidity and mortality rates in susceptible birds. IBDV-pathogenesis studies have focused mainly on primary lymphoid organs. It is not known if IBDV infection may modify the development of the gut associated lymphoid tissues (GALT) as well as the microbiota composition. The aim of the present study was to investigate the effects of IBDV-infection on the bursa of Fabricius (BF), caecal tonsils (CT) and caecum, and to determine the effects on the gut microbiota composition in the caecum. Commercial broiler chickens were inoculated with a very virulent (vv) strain of IBDV at 14 (Experiment 2) or 15 (Experiment 1) days post hatch (dph). Virus replication, lesion development, immune parameters including numbers of T and B lymphocytes, macrophages, as well as the gut microbiota composition were compared between groups. Rapid IBDV-replication was detected in the BF, CT and caecum. It was accompanied by histological lesions including an infiltration of heterophils. In addition a significant reduction in the total mucosal thickness of the caecum was observed in vvIBDV-infected birds compared to virus-free controls (P < 0.05). vvIBDV infection also led to an increase in T lymphocyte numbers and macrophages, as well as a decrease in the number of B lymphocytes in the lamina propria of the caecum, and in the caecal tonsils. Illumina sequencing analysis indicated that vvIBDV infection also induced changes in the abundance of Clostridium XIVa and Faecalibacterium over time. Overall, our results suggested that vvIBDV infection had a significant impact on the GALT and led to a modulation of gut microbiota composition, which may lead to a higher susceptibility of affected birds for pathogens invading through the gut.

Effects of host genetics and environmental conditions on fecal microbiota composition of pigs.

Since microbiota may influence the physiology of its host including body weight increase, growth rate or feed intake, in this study we determined the microbiota composition in high or low residual feed intake (HRFI and LRFI) pig lines, of different age and/or subjected to sanitary stress by sequencing the V3/V4 variable region of 16S rRNA genes. Allisonella, Megasphaera, Mitsuokella, Acidaminococcus (all belonging to Firmicutes/class Negativicutes), Lactobacillus, Faecalibacterium, Catenibacterium, Butyrivibrio, Erysipelotrichaceae, Holdemania, Olsenella and Collinsella were more abundant in HRFI pigs. On the other hand, 26 genera including Bacteroides, Clostridium sensu stricto, Oscillibacter, Paludibacter, Elusimicrobium, Bilophila, Pyramidobacter and TM7 genera, and Clostridium XI and Clostridium XIVa clusters were more abundant in LRFI than HRFI pigs. Adaptation of microbiota to new diet after weaning was slower in LRFI than in HRFI pigs. Sanitary stress was of relatively minor influence on pig microbiota composition in both tested lines although abundance of Helicobacter increased in LRFI pigs subjected to stress. Selection for residual feed intake thus resulted in a selection of fecal microbiota of different composition. However, we cannot conclude whether residual feed intake was directly affected by different microbiota composition or whether the residual feed intake and microbiota composition are two independent consequences of yet unknown genetic traits differentially selected in the pigs of the two lines.

Infectious bursal disease virus inoculation infection modifies Campylobacter jejuni-host interaction in broilers.

BACKGROUND: Campylobacter jejuni is considered as a chicken commensal. The gut microbiota and the immune status of the host may affect its colonization. Infectious bursal disease virus (IBDV) is an immunosuppressive virus of chickens, which allows secondary pathogens to invade or exacerbates their pathogenesis. To investigate the effect of IBDV-induced immunosuppression on the pathogenesis of C. jejuni, broiler chickens were inoculated with a very virulent (vv) strain of IBDV at 14 days post hatch followed by C. jejuni inoculation at 7 (Experiment A) or 9 (Experiment B) days post virus (IBDV) inoculation. RESULTS: vvIBDV-infection led to a depression in caecal lamina propria B lymphocytes and the anti-C. jejuni-antibody response starting at 14 days post C. jejuni inoculation (pbi). The C. jejuni-colonization pattern was comparable between mono-inoculated groups of both experiments, but it varied for vvIBDV + C. jejuni co-inoculated groups. In Experiment A significant higher numbers of colony forming units (CFU) of C. jejuni were detected in the caecum of co-inoculated birds compared to C. jejuni-mono-inoculated birds in the early phase after C. jejuni-inoculation. In Experiment B the clearance phase was affected in the co-inoculated group with significantly higher CFU at 21 days pbi compared to the mono-inoculated group (P < 0.05). No major differences were seen in numbers local lamina propria T lymphocyte populations between C. jejuni-inoculated groups with or without vvIBDV-infection. Interestingly, both pathogens affected the microbiota composition. The consequences of these microflora changes for the host have to be elucidated further. CONCLUSION: Our data suggests that the timing between viral and bacterial infection might affect the outcome of C. jejuni colonization differently. Our results confirm previous studies that anti-Campylobacter-antibodies may specifically be important for the clearance phase of the bacteria. Therefore, as vvIBDV is widely distributed in the field, it may have a significant impact on the colonization and shedding rate of C. jejuni in commercial poultry flocks. Subsequently, successful IBDV-control strategies may indirectly also benefit the gut-health of chickens.