Abstract:Tylosin phosphate is a macrolide commonly administered to cattle in North America for the control of liver abscesses. This study investigated the effect of in-feed administration of tylosin phosphate to cattle at subtherapeutic levels and its subsequent withdrawal on macrolide resistance using enterococci as an indicator bacterium. Fecal samples were collected from steers that received no antibiotics and steers administered tylosin phosphate (11 ppm) in-feed for 197 days and withdrawn 28 days before slaughter.… Show more
“…The assembled tree was consistent with the PFGE profile dendrogram observed from our previous study [10]. As expected, clustering was observed for genomes of the same species further verifying the identity of each species based on previous groES-EL spacer speciation [10]. Fig.…”
Section: Resultssupporting
confidence: 89%
“…isolated from bovine feces including E. hirae ( n = 10), E. faecium ( n = 3), E. villorum ( n = 2), E. casseliflavus ( n = 2), E. faecalis ( n = 1), E. durans ( n = 1), E. gallinarum ( n = 1) and E. thailandicus ( n = 1) were selected for whole genome sequencing (Table 1). These were selected from an archive of isolates collected between 2004 and 2005, which were previously characterized by PFGE and antimicrobial susceptibility testing [10]. At least one representative of each species isolated from bovine feces was selected, and for E. hirae and E. faecium , selection was based on maximizing diversity as measured by PFGE profiles as well as selecting isolates that displayed unique antimicrobial resistance profiles.…”
Background
Enterococcus is ubiquitous in nature and is a commensal of both the bovine and human gastrointestinal (GI) tract. It is also associated with clinical infections in humans. Subtherapeutic administration of antibiotics to cattle selects for antibiotic resistant enterococci in the bovine GI tract. Antibiotic resistance genes (ARGs) may be present in enterococci following antibiotic use in cattle. If located on mobile genetic elements (MGEs) their dissemination between Enterococcus species and to pathogenic bacteria may be promoted, reducing the efficacy of antibiotics.ResultsWe present a comparative genomic analysis of twenty-one Enterococcus spp. isolated from bovine feces including Enterococcus hirae (n = 10), Enterococcus faecium (n = 3), Enterococcus villorum (n = 2), Enterococcus casseliflavus (n = 2), Enterococcus faecalis (n = 1), Enterococcus durans (n = 1), Enterococcus gallinarum (n = 1) and Enterococcus thailandicus (n = 1). The analysis revealed E. faecium and E. faecalis from bovine feces share features with human clinical isolates, including virulence factors. The Tn917 transposon conferring macrolide-lincosamide-streptogramin B resistance was identified in both E. faecium and E. hirae, suggesting dissemination of ARGs on MGEs may occur in the bovine GI tract. An E. faecium isolate was also identified with two integrative conjugative elements (ICEs) belonging to the Tn916 family of ICE, Tn916 and Tn5801, both conferring tetracycline resistance.ConclusionsThis study confirms the presence of enterococci in the bovine GI tract possessing ARGs on MGEs, but the predominant species in cattle, E. hirae is not commonly associated with infections in humans. Analysis using additional complete genomes of E. faecium from the NCBI database demonstrated differential clustering of commensal and clinical isolates, suggesting that these strains may be specifically adapted to their respective environments.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-017-0962-1) contains supplementary material, which is available to authorized users.
“…The assembled tree was consistent with the PFGE profile dendrogram observed from our previous study [10]. As expected, clustering was observed for genomes of the same species further verifying the identity of each species based on previous groES-EL spacer speciation [10]. Fig.…”
Section: Resultssupporting
confidence: 89%
“…isolated from bovine feces including E. hirae ( n = 10), E. faecium ( n = 3), E. villorum ( n = 2), E. casseliflavus ( n = 2), E. faecalis ( n = 1), E. durans ( n = 1), E. gallinarum ( n = 1) and E. thailandicus ( n = 1) were selected for whole genome sequencing (Table 1). These were selected from an archive of isolates collected between 2004 and 2005, which were previously characterized by PFGE and antimicrobial susceptibility testing [10]. At least one representative of each species isolated from bovine feces was selected, and for E. hirae and E. faecium , selection was based on maximizing diversity as measured by PFGE profiles as well as selecting isolates that displayed unique antimicrobial resistance profiles.…”
Background
Enterococcus is ubiquitous in nature and is a commensal of both the bovine and human gastrointestinal (GI) tract. It is also associated with clinical infections in humans. Subtherapeutic administration of antibiotics to cattle selects for antibiotic resistant enterococci in the bovine GI tract. Antibiotic resistance genes (ARGs) may be present in enterococci following antibiotic use in cattle. If located on mobile genetic elements (MGEs) their dissemination between Enterococcus species and to pathogenic bacteria may be promoted, reducing the efficacy of antibiotics.ResultsWe present a comparative genomic analysis of twenty-one Enterococcus spp. isolated from bovine feces including Enterococcus hirae (n = 10), Enterococcus faecium (n = 3), Enterococcus villorum (n = 2), Enterococcus casseliflavus (n = 2), Enterococcus faecalis (n = 1), Enterococcus durans (n = 1), Enterococcus gallinarum (n = 1) and Enterococcus thailandicus (n = 1). The analysis revealed E. faecium and E. faecalis from bovine feces share features with human clinical isolates, including virulence factors. The Tn917 transposon conferring macrolide-lincosamide-streptogramin B resistance was identified in both E. faecium and E. hirae, suggesting dissemination of ARGs on MGEs may occur in the bovine GI tract. An E. faecium isolate was also identified with two integrative conjugative elements (ICEs) belonging to the Tn916 family of ICE, Tn916 and Tn5801, both conferring tetracycline resistance.ConclusionsThis study confirms the presence of enterococci in the bovine GI tract possessing ARGs on MGEs, but the predominant species in cattle, E. hirae is not commonly associated with infections in humans. Analysis using additional complete genomes of E. faecium from the NCBI database demonstrated differential clustering of commensal and clinical isolates, suggesting that these strains may be specifically adapted to their respective environments.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-017-0962-1) contains supplementary material, which is available to authorized users.
“…Another study found that sub-therapeutic tylosin treatment (Tylan, Elanco; 11 mg/kg in-feed) increased the frequency of Enterococcus spp. harboring erm (B) and/or msrC (a macrolide/streptogramin efflux pump gene) [171]. The authors of that study concluded that the diversity of Enterococcus decreased in the period between when cattle entered and exited the feedlot, and that the AMR Enteroccocus were derived from strains present in the intestinal microbiota before tylosin administration [171].…”
Section: Antimicrobials and The Bovine Microbiotamentioning
Antimicrobials are critical to contemporary high-intensity beef production. Many different antimicrobials are approved for beef cattle, and are used judiciously for animal welfare, and controversially, to promote growth and feed efficiency. Antimicrobial administration provides a powerful selective pressure that acts on the microbial community, selecting for resistance gene determinants and antimicrobial-resistant bacteria resident in the bovine flora. The bovine microbiota includes many harmless bacteria, but also opportunistic pathogens that may acquire and propagate resistance genes within the microbial community via horizontal gene transfer. Antimicrobial-resistant bovine pathogens can also complicate the prevention and treatment of infectious diseases in beef feedlots, threatening the efficiency of the beef production system. Likewise, the transmission of antimicrobial resistance genes to bovine-associated human pathogens is a potential public health concern. This review outlines current antimicrobial use practices pertaining to beef production, and explores the frequency of antimicrobial resistance in major bovine pathogens. The effect of antimicrobials on the composition of the bovine microbiota is examined, as are the effects on the beef production resistome. Antimicrobial resistance is further explored within the context of the wider beef production continuum, with emphasis on antimicrobial resistance genes in the food chain, and risk to the human population.
“…Additionally, a study by Meyer et al () studied the effects of essential oils as alternatives which tended to reduce liver abscesses in comparison with the control animals, though not significantly ( P > 0·05). Beukers et al () suggested that early withdrawal of tylosin prior to slaughter contributed to a lower proportion of macrolide‐resistant enterococci. Additionally, Müller et al () noted that the environment where cattle are raised, namely where antibiotics have previously been used, seemed to play a large role in the presence of macrolide‐resistant enterococci.…”
Enterococci are included in the United States National Antimicrobial Resistance Monitoring System to track antibiotic resistance among commensal Gram‐positive enteric bacteria, largely due to their high abundance in food animals and in retail meat. In the U.S. cattle industry, macrolides are used to prevent and control liver abscesses, which cause significant economic losses. Previous studies have suggested that feeding tylosin and the intensity of the pen environment, both expand and sustain respectively the prevalence of multidrug resistance among enterococci in feedlot cattle. This has led to research into alternative feed supplements and improved stewardship practices. In a randomized controlled trial, we measured the impact of a probiotic and an altered pen environment on antimicrobial resistance among faecal Enterococcus spp. in cattle fed tylosin. Supplementing cattle with an Enterococcus faecium and Saccharomyces cerevisiae‐based probiotic yielded the isolation of E. faecium of the probiotic sequence type (ST296) from faecal and environmental samples in treatment groups, as well as from cattle and the manure pack in nearby pens. Of importance, the probiotic strain also was found in a desiccated and milled manure pack sample taken 120 days after the initial trial ended. Phylogenetic and SNP analyses revealed clonal survival and spread compatible with faecal‐environmental‐oral recycling of the probiotic strain within and among cattle and pens. The increase in prevalence of the ST296 strain occurred concomitant with a decrease in ST240, the dominant sequence type associated with ermB and tet(M) resistance genes in this trial.
Significance and Impact of the Study
We demonstrate that a macrolide‐susceptible probiotic Enterococcus faecium ST296 strain fed to beef cattle becomes fully embedded in the microbial community cycling of bacteria via faecal‐environmental‐oral transmission within and among feedlot pens. An initial investment in feeding the probiotic is thereby leveraged into expanding numbers of susceptible bacteria in cattle and their environment, even among those cattle fed tylosin.
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