Abstract
BackgroundThe intestinal tract is a rich and complex environment and its microbiota has been shown to have an important role in health and disease in the host. Several factors can cause disruption of the normal intestinal microbiota, including antimicrobial therapy, which is an important cause of diarrhea in horses. This study aimed to characterize changes in the fecal bacterial populations of healthy horses associated with the administration of frequently used antimicrobial drugs.ResultsTwenty-four adult mares were assigned to receive procaine penicillin intramuscularly (IM), ceftiofur sodium IM, trimethoprim sulfadiazine (TMS) orally or to a control group. Treatment was given for 5 consecutive days and fecal samples were collected before drug administration (Day 1), at the end of treatment (Days 5), and on Days 14 and 30 of the trial. High throughput sequencing of the V4 region of the 16S rRNA gene was performed using an Illumina MiSeq sequencer. Significant changes of population structure and community membership were observed after the use of all drugs. TMS caused the most marked changes on fecal microbiota even at higher taxonomic levels including a significant decrease of richness and diversity. Those changes were mainly due to a drastic decrease of Verrucomicrobia, specifically the “5 genus incertae sedis”. Changes in structure and membership caused by antimicrobial administration were specific for each drug and may be predictable. Twenty-five days after the end of treatment, bacterial profiles were more similar to pre-treatment patterns indicating a recovery from changes caused by antimicrobial administration, but differences were still evident, especially regarding community membership.ConclusionsThe use of systemic antimicrobials leads to changes in the intestinal microbiota, with different and specific responses to different antimicrobials. All antimicrobials tested here had some impact on the microbiota, but TMS significantly reduced bacterial species richness and diversity and had the greatest apparent impact on population structure, specifically targeting members of the Verrucomicrobia phylum.Electronic supplementary materialThe online version of this article (doi:10.1186/s12917-015-0335-7) contains supplementary material, which is available to authorized users.
Highlights
The intestinal tract is a rich and complex environment and its microbiota has been shown to have an important role in health and disease in the host
The results indicate that after 14 and 30 days population structures were still different from the beginning of the trial
Considering each group individually, penicillin had no impact on population structure and community membership evaluated by the Parsimony test, but a significant difference was identified using Analysis of molecular variance (AMOVA)
Summary
The intestinal tract is a rich and complex environment and its microbiota has been shown to have an important role in health and disease in the host. Several factors can cause disruption of the normal intestinal microbiota, including antimicrobial therapy, which is an important cause of diarrhea in horses. The intestinal microbiota performs important roles in the maintenance of health and on the pathophysiology of several diseases [1]. The intestinal bacterial microbiota is important due to its role in cellulose fermentation and short chain fatty acid production, which comprise the main energy sources for this animal species [2]. Of special interest are the effects of antimicrobials, as this group of drugs can have major impact on the intestinal microbiota of horses [15], and colitis is an important (and potentially life-threatening) complication of antimicrobial exposure in this species [16,17,18].
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