Effect of dietary iron supplementation on the equine fecal microbiome.

Iron is an essential element for all living organisms, including bacteria, as several virulence factors and replication components are influenced by iron concentration. The objective of this study was to determine whether the composition and diversity of the fecal microbiota of adult horses are affected by supplemental dietary iron. Ten clinically healthy horses were randomly divided into a control and an iron-supplemented group (n = 5). The treated group was supplemented with oral ferrous sulphate monohydrate (720 ppm of iron), whereas the control group received 320 ppm of iron daily for 15 d. Fecal samples were collected before and 5, 10, 15, and 30 d after supplementation and frozen at -80°C. DNA was sequenced using an Illumina MiSeq platform and data were analyzed using the software Mothur and linear discriminant analysis (LDA) effect size (LEfSe). Iron supplementation caused no change in the overall composition of the fecal microbiota, but some minor changes were observed in the low-abundant bacteria, as well as an increased alpha diversity after 15 d of supplementation. Significant differences in community composition of the fecal microbiota over time were observed in both groups, highlighting the importance of a control group, as there are variables that cannot be controlled in microbiome studies.

Le fer est un élément essentiel pour tous les organismes vivants, y compris les bactéries, car plusieurs facteurs de virulence et composants de réplication sont influencés par la concentration en fer. L'objectif de cette étude était de déterminer si la composition et la diversité du microbiote fécal des chevaux adultes sont affectées par la supplémentation en fer alimentaire. Dix chevaux cliniquement sains ont été divisés au hasard en un groupe témoin et un groupe supplémenté en fer, n = 5 par groupe. Le groupe traité a reçu un supplément oral de sulfate ferreux monohydraté (720 ppm de fer) et le groupe témoin a reçu 320 ppm de fer par jour pendant 15 jours. Des échantillons fécaux ont été prélevés avant la supplémentation et 5, 10, 15 et 30 jours après la supplémentation puis congelés à −80 °C. L'ADN a été séquencé à l'aide de la plateforme Illumina MiSeq et les données ont été analysées à l'aide des logiciels Mothur et analyse de la fonction discriminante linéaire taille de l'effet LefSe. La supplémentation en fer n'a provoqué aucun changement dans la composition du microbiote fécal, mais certains changements ont été observés chez les bactéries peu abondantes, ainsi qu'une augmentation de la diversité alpha après 15 jours de supplémentation. Au fil du temps, des différences significatives dans la composition de la communauté bactérienne ont été observées dans les deux groupes, soulignant l'importance d'un groupe témoin, car il existe des variables qui ne peuvent être contrôlées dans les études sur le microbiome.(Traduit par les auteurs).

Comparison of microbial populations in the small intestine, large intestine and feces of healthy horses using terminal restriction fragment length polymorphism.

BACKGROUND: The composition of the microbiota of the equine intestinal tract is complex. Determining whether the microbial composition of fecal samples is representative of proximal compartments of the digestive tract could greatly simplify future studies. The objectives of this study were to compare the microbial populations of the duodenum, ileum, cecum, colon and rectum (feces) within and between healthy horses, and to determine whether rectal (fecal) samples are representative of proximal segments of the gastrointestinal tract. Intestinal samples were collected from ten euthanized horses. 16S rRNA gene PCR-based TRFLP was used to investigate microbiota richness in various segments of the gastrointestinal tract, and dice similarity indices were calculated to compare the samples. RESULTS: Within horses large variations of microbial populations along the gastrointestinal tract were seen. The microbiota in rectal samples was only partially representative of other intestinal compartments. The highest similarity was obtained when feces were compared to the cecum. Large compartmental variations were also seen when microbial populations were compared between six horses with similar dietary and housing management. CONCLUSION: Rectal samples were not entirely representative of intestinal compartments in the small or large intestine. This should be taken into account when designing studies using fecal sampling to assess other intestinal compartments. Similarity between horses with similar dietary and husbandry management was also limited, suggesting that parts of the intestinal microbiota were unique to each animal in this study.

Presence and molecular characterization of Clostridium difficile and Clostridium perfringens in intestinal compartments of healthy horses.

BACKGROUND: Clostridium difficile and Clostridium perfringens are commonly associated with colitis in equids, but healthy carriers exist. Scarce information is available on the prevalence of Clostridium spp. in gastrointestinal compartments other than faeces in healthy horses, and it is unknown whether faecal samples are representative of proximal compartments. The objectives were to investigate the prevalence of C. difficile and C. perfringens in different intestinal compartments of healthy adult horses and to determine whether faecal samples are representative of colonization in proximal sites and overall carrier status. RESULTS: Toxigenic C. difficile was isolated from 14/135 (10.3%) samples from 8/15 (53.3%) horses. Between zero and three sites were positive per horse, and multiple sites were positive in four horses. Isolates were recovered from duodenum, jejunum, ileum, right dorsal colon, small colon and rectum. When multiple compartments were positive in a single horse, two different C. difficile ribotypes were always present. Clostridium perfringens Type A (CPE, ß2 toxin gene negative) was recovered from the left ventral colon of one horse (0.74%, 1/135 samples). Agreement between faeces and overall C. difficile carrier status was good. CONCLUSIONS: Clostridium difficile can be found in different compartments of the gastrointestinal tract of healthy horses, and multiple strains can be present in an individual horse. The prevalence of C. perfringens in healthy adult hoses was low, consistent with previous reports. Faecal samples were representative for presence of C. difficile in proximal compartments in 5/8 horses (63%) but were not representative for the specific strain.