Assessing the Risk of Antimicrobial Resistant Enterococcal Infections in Humans Due to Bacitracin Usage in Poultry.

Bacitracin is an antimicrobial used in the feed or water of poultry in the U.S. for the prevention, treatment, and control of clostridial diseases such as necrotic enteritis. Concern has been raised that bacitracin can select for antimicrobial-resistant bacteria that can be transmitted to humans and subsequently cause disease that is more difficult to treat because of the resistance. The objective of the present study was to perform a quantitative risk assessment (QRA) to estimate the potential risk in the U.S. of human infection with antimicrobial-resistant Enterococcus faecalis and E. faecium derived from chicken and turkey products as a result of bacitracin usage in U.S. poultry. The modeling approach estimated the annual number of healthcare-associated enterococcal infections in the U.S. that would be resistant to antimicrobial therapy and that would be derived from poultry sources because of bacitracin use in poultry. Parameter estimates were developed to be "maximum risk" to overestimate the risk to humans. While approximately 60% of E. faecalis and E. faecium derived from poultry were predicted to possess bacitracin resistance based on the presence of the bcrABDR gene locus, very few human-derived isolates possessed this trait. Furthermore, no vancomycin or linezolid-resistant strains of E. faecalis or E. faecium were detected in poultry sources between the years 2002 and 2019. The model estimated the number of antimicrobial-resistant E. faecalis and E. faecium cases per year that might resist therapy due to bacitracin use in poultry as 0.86 and 0.14, respectively, which translates to an annual risk estimate for E. faecalis of less than 1 in 350 million and for E. faecium of less than 1 in 2 billion for members of the U.S. population. Even with the use of risk-maximizing assumptions, the results indicate that there is a high probability that the use of bacitracin according to label instructions in U.S. poultry presents a negligible risk to human health.

Animal drug shortages limit veterinary therapeutic options and introduce artifacts in antimicrobial sales reporting.

Supply chain issues disrupt veterinary care and cause downstream consequences that alter the practice of veterinary medicine. Antimicrobials are just 1 class of pharmaceuticals that have been impacted by supply chain issues over the last couple of years. Since February 2021, 2 sponsors/manufacturers of penicillin products have reported shortages in the active pharmaceutical ingredient. With the release of the 2021 Summary Report on Antimicrobials Sold or Distributed for Use in Food-Producing Animals by the FDA, a key finding was a 19% decrease in penicillin sales and distribution from 2020 to 2021. Herein, we provide our clinicians' professional perspective regarding how drug shortages, specifically that of penicillin, might contribute to misconstrued patterns in antimicrobial use and what can be done by veterinarians and the FDA to minimize the impact of an antimicrobial drug shortage on animal health and well-being.

Health of wild fish exposed to contaminants of emerging concern in freshwater ecosystems utilized by a Minnesota Tribal community.

Fish serve as indicators of exposure to contaminants of emerging concern (CECs)-chemicals such as pharmaceuticals, hormones, and personal care products-which are often designed to impact vertebrates. To investigate fish health and CECs in situ, we evaluated the health of wild fish exposed to CECs in waterbodies across northeastern Minnesota with varying anthropogenic pressures and CEC exposures: waterbodies with no human development along their shorelines, those with development, and those directly receiving treated wastewater effluent. Then, we compared three approaches to evaluate the health of fish exposed to CECs in their natural environment: a refined fish health assessment index, a histopathological index, and high-throughput (ToxCast) in vitro assays. Lastly, we mapped adverse outcome pathways (AOPs) associated with identified ToxCast assays to determine potential impacts across levels of biological organization within the aquatic system. These approaches were applied to subsistence fish collected from the Grand Portage Indian Reservation and 1854 Ceded Territory in 2017 and 2019. Overall, 24 CECs were detected in fish tissues, with all but one of the sites having at least one detection. The combined implementation of these tools revealed that subsistence fish exposed to CECs had histological and macroscopic tissue and organ abnormalities, although a direct causal link could not be established. The health of fish in undeveloped sites was as poor, or sometimes poorer, than fish in developed and wastewater effluent-impacted sites based on gross and histologic tissue lesions. Adverse outcome pathways revealed potential hazardous pathways of individual CECs to fish. A better understanding of how the health of wild fish harvested for consumption is affected by CECs may help prioritize risk management research efforts and can ultimately be used to guide fishery management and public health decisions. Integr Environ Assess Manag 2024;20:846-863. © 2023 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Biodegradation, photolysis, and sorption of antibiotics in aquatic environments: A scoping review.

The presence of antibiotics in surface waters is a potential driver of antibiotic resistance and thus of concern to human and environmental health. Key factors driving the potential impact of antibiotics are their persistence and transport in rivers and lakes. The goal of this study was to describe the peer-reviewed published literature on the photolysis (direct and indirect), sorption, and biodegradation of a selected group of antibiotic compounds following a scoping review methodology. Primary research from 2000 to 2021 was surveyed to compile information on these processes for 25 antibiotics from 6 classes. After compilation and assessment of the available parameters, the results indicate that information is present to predict the rates of direct photolysis and reaction with hydroxyl radical (an indirect photolysis process) for most of the selected antibiotics. There is insufficient or inconsistent information for including other indirect photolysis processes, biodegradation, or removal via sorption to settling particles for most of the targeted antibiotic compounds. Future research should focus on collecting fundamental parameters such as quantum yields, second-order rate constants, normalized biodegradation rates, and organic carbon or surface area normalized sorption coefficients rather than pseudo-first order rate constants or sorption equilibrium constants that apply only to specific conditions/sites.

On-farm antimicrobial usage in commercial turkey production in the United States, 2013-2021.

A key component of antimicrobial stewardship is the ability to collect antimicrobial use data and ultimately use this information to ensure that administrations are necessary and effective. National antimicrobial sales data cannot help in this capacity because the data lack context, for example, details concerning target species and disease indication. The objective of this study was to continue the development of a system for collecting flock-level on-farm antimicrobial use data from the U.S. turkey industry and to have it be representative of national turkey production in the U.S. This study utilized a public-private partnership to enable collection and protection of sensitive flock-level data from an extremely large industry while releasing deidentified and aggregated information regarding the details of antimicrobial use on U.S. turkey farms over time. Participation was voluntary. Data were collected for the period 2013 through 2021 and are reported on a calendar year basis. Using production statistics from USDA:NASS as a denominator, the data supplied by participating companies represented approximately 67.3% of turkey production in the U.S. in 2013, approximately 69.1% in 2017, and approximately 71.4% in 2021. The data that were submitted for 2021 are based on approximately 149,000,192 turkeys slaughtered and 4,929,773,506 pounds liveweight produced. Detailed prescription records representing approximately 60-70% of the birds were available for the 2018-2021 dataset. The estimated percentage of turkey poults placed that received hatchery antimicrobials decreased from 96.9% in 2013 to 40.5% in 2021. The use of in-feed antimicrobials was practically eliminated, with in-feed tetracycline being the only medically important antimicrobial used in 2021. Use of in-feed tetracyclines decreased approximately 80% between 2013 and 2021. Water-soluble antimicrobial use declined over the study period. Between 2013 and 2021, water-soluble penicillin use decreased approximately 41% but water-soluble tetracycline use increased approximately 22%. Key diseases that were treated with water-soluble antimicrobials included bacterial poult enteritis and clostridial dermatitis. Efforts to reduce the incidence of these diseases would reduce the need for antimicrobial therapy, thereby enabling continued decreases in antimicrobial use without sacrificing animal welfare. However, this will require an investment in research to find efficacious and cost-effective mitigation strategies.

Antimicrobial usage in broiler chicken production in the United States, 2013-2021.

Although efforts to improve antimicrobial stewardship should include the collection of antimicrobial use data, most antimicrobial datasets collected at the national level consist of antimicrobial sales data which cannot inform stewardship. These data lack context, such as information regarding target species, disease indication, and regimen specifics like dose, route and duration. Therefore, the goal of this study was to develop a system for collecting data on the use of antimicrobials in the U.S. broiler chicken industry. This study utilized a public-private partnership to enable collection and protection of sensitive data from an extremely large industry while releasing deidentified and aggregated information regarding the details of antimicrobial use on U.S. broiler chicken farms over time. Participation was voluntary. Data were collected for the period 2013 through 2021 and are reported on a calendar year basis. Using production statistics from USDA:NASS as a denominator, the data supplied by participating companies represented approximately 82.1% of broiler chicken production in the U.S. in 2013, approximately 88.6% in 2017, and approximately 85.0% in 2021. The data that were submitted for 2021 are based on approximately 7,826,121,178 chickens slaughtered and 50,550,817,859 pounds liveweight produced. Granular flock-level treatment records were available for 75-90% of the birds represented in the 2018-2021 dataset. There was no use of antimicrobials in the hatchery for the years 2020 and 2021. Medically important in-feed antimicrobial use decreased substantially, with all in-feed tetracycline use being eliminated by 2020, and the use of virginiamycin being reduced by more than 97% since 2013. Medically important water-soluble antimicrobials are used for the treatment of disease in broiler production. Use decreased substantially for most water-soluble antimicrobials. The most important diseases necessitating treatment were necrotic enteritis and gangrenous dermatitis as well as E. coli-related disease. A focus on reducing the incidence of these diseases would reduce the need for antimicrobial therapy but will require an investment in research to find efficacious and cost-effective interventions for these diseases.

Efficacy of Antibiotic and Non-antibiotic Interventions in Preventing and Treating Necrotic Enteritis in Broiler Chickens: A Systematic Review.

The objective of this systematic review was to compare the efficacy of antibiotic and non-antibiotic alternatives in the prevention and treatment of necrotic enteritis (NE) in broiler chickens. In vivo experimental and observational studies that compared the administration of non-antibiotic compounds with antibiotics to prevent or treat NE in broiler chickens and that evaluated mortality and/or clinical or subclinical NE outcome measures were eligible. Four electronic databases were searched in December 2019 and updated in October 2021. Retrieved studies were evaluated in two phases: abstract and design screening. Data were then extracted from included studies. Risk of bias was assessed by outcome following the Cochrane Risk of Bias 2.0 tool. A meta-analysis was not conducted due to heterogeneity across interventions and outcomes. The non-antibiotic and antibiotic groups were compared at the outcome level for individual studies using the mean difference and 95% confidence interval (CI) calculated post hoc from raw data. In total, 1282 studies were originally identified, and 40 were included in the final review. The overall risk of bias for the 89 outcomes was either "high" (n = 34) or "some concerns" (n = 55). Individual study comparisons showed a beneficial trend toward the antibiotic group for reduced mortality, NE lesion scores (overall, jejunum, and ileum), Clostridium perfringens counts, and for most histologic measurements (duodenum, jejunum, and ileum villi height, and jejunum and ileum crypt depth). The non-antibiotic groups showed a beneficial trend for NE duodenum lesion scores and duodenum crypt depth measurements. Based on this review, there is a trend that mostly favors antibiotic compounds in preventing and/or treating NE, but the evidence also suggests no difference when comparing them with non-antibiotic alternatives. Studies assessing this research question were heterogeneous in their intervention conditions and outcomes measured, and there were key aspects of the experimental design not reported in some of the studies.

Eficacia de las intervenciones con antibióticos y compuestos no antibióticos para prevenir y tratar la enteritis necrótica en pollos de engorde: Una revisión sistemática El objetivo de esta revisión sistemática fue comparar la eficacia de antibióticos y alternativas a los antibióticos en la prevención y tratamiento de la enteritis necrótica (NE) en pollos de engorde. Se incluyeron estudios experimentales in vivo y estudios observacionales que compararon la administración de compuestos no considerados antibióticos con compuestos antibióticos usados para prevenir o tratar la enteritis necrótica en pollos de engorde, y que evaluaran mortalidad, signos clínicos, u otros resultados subclínicos. Se buscaron referencias en cuatro bases de datos bibliográficos en Diciembre de 2019 y por segunda vez en Octubre de 2021. Los estudios que se encontraron se evaluaron en dos fases: resumen y diseño del estudio de escrutinio. Posteriormente se extrajeron los datos de aquellos estudios que se incluyeron después del escrutinio. Se evaluó el riesgo de sesgos siguiendo la herramienta de Cochrane Risk of Bias 2.0. No se pudo realizar un meta-análisis debido a la heterogeneidad de las intervenciones y de los resultados de los estudios incluidos. Los grupos de compuestos no antibióticos y de antibióticos se compararon con base a los resultados individuales de cada estudio usando la diferencia entre medias e intervalos de confianza al 95%, calculados post-hoc usando los datos originales. Se identificaron un total de 1282 estudios, y 40 fueron finalmente incluidos en la revisión. El riesgo de sesgos para el total de los 89 resultados individuales fue alto (n = 34) o con "ciertos problemas" (n = 55). Las comparaciones individuales entre estudios mostraron una tendencia beneficiosa hacia el grupo de antibióticos en términos de mortalidad reducida, puntaje de lesiones de enteritis necrótica (total, yeyuno e íleo), conteos de Clostridium perfringens, así como para la mayoría de las medidas histológicas (altura de las vellosidades del duodeno, yeyuno e íleo, y profundidad de la cripta del yeyuno e íleo). El grupo de no antibióticos mostró una tendencia beneficiosa para el puntaje de lesiones de enteritis necrótica del duodeno y para las medidas de profundidad de la cripta del duodeno. Según esta revisión, hay una tendencia que favorece al grupo de antibióticos en la prevención y/o tratamiento de enteritis necrótica, pero la evidencia también sugiere que no hay diferencia entre los grupos. Los estudios incluidos en la comparación eran muy heterogéneos en cuanto a las condiciones de las intervenciones y a los resultados que se midieron, además de que algunos aspectos importantes del diseño experimental en algunos de los estudios no se reportaron.

Antimicrobial use in 20 U.S. beef feedyards: 2018-2019.

The objective of this study was to report antimicrobial use in a convenience sample of U.S. beef feedyards for the years 2018 and 2019. In addition to antimicrobial use metrics, also reported are the indications for antimicrobial use and outcomes related to these indications. Antimicrobial use is characterized at the study and feedyard levels for a total of 1,141,846 head of cattle in 20 U.S. feedyards. Antimicrobial use is reported as milligrams of active antimicrobial ingredient per kilogram of liveweight sold (mg/kg-LW) and regimens of antimicrobials per animal year (Reg/AY). Regimens are described by antimicrobial class within use category as characterized by mg of active antimicrobial product per regimen (mg/Reg) and calendar days of administration per regimen (CDoA/Reg). A total of 1,128,515 regimens of medically important antimicrobials were captured from records. The number of regimens/100 head-in (Reg/100 head-in) are described in a subset of 10 feedyards with adequate data granularity to directly determine indications for antimicrobial administration. For the indications of bovine respiratory disease (BRD), Lameness (Lame), Liver Abscess Control (LAC), and Other (e.g., central nervous system disease, cellulitis) the Reg/100 head-in study-level values are 37.1, 0.8, 98.4, and 0.7, respectively, for 2018, with similar values for 2019. The regimens for BRD are further categorized in these 10 feedyards by the use categories in-feed, control of BRD, and individual animal therapy, yielding study level values of 4.6, 19.6, and 12.9 Reg/100 head-in, respectively, for 2018, with similar values for 2019. Outcomes of therapy for individual animal treatment of BRD, Lame, and Other are reported as treatment success, retreatment, or mortality by 30 days after the initial therapy of an animal for a disease. Treatment success rates (no treatment or mortality in the next 30 days) for 2018 in the 10 feedyards with sufficient data granularity are 76.5, 86.5, and 83.0% for BRD, Lame, and Other, respectively. The comparison of these results with other reports of antimicrobial use in North American feedyards highlights how differing approaches in calculating metric values may result in substantially different conclusions regarding antimicrobial use, especially in relation to long-duration uses.

Estimates of on-farm antimicrobial usage in egg production in the United States, 2016-2021.

Very few data exist globally regarding the use of antimicrobials in the table egg industry. Antimicrobial use data from broiler chickens and turkeys cannot be used as a surrogate of layer chickens because of the fact that table eggs for human consumption are produced daily by laying hens. To avoid the possibility of antimicrobial residues in the eggs, there are very few antimicrobials approved for use in layers in the U.S. The objective of this study was to collect on-farm antimicrobial use data from the U.S. table egg industry and to have it be representative of the national layer flock. Participation was voluntary. Data were collected for the period 2016 through 2021 and are reported on a calendar year basis. Using production statistics from USDA:NASS as a denominator, the data supplied by participating companies accounted for 3,016,183,140 dozen eggs (~40% of national egg production) in 2016 and 3,556,743,270 dozen eggs (~45% of national egg production) in 2021. All of the replacement chicks placed on pullet farms during the study period were estimated to have received 0.2 mg/chick gentamicin at the hatchery. Most of the antimicrobial administration in U.S. egg production is via the feed. The ionophores monensin and salinomycin were used in the pullets, bacitracin was used in both pullets and layers (primarily for control of necrotic enteritis), and chlortetracycline was used primarily in layers for the treatment of E. coli-related disease. In the layers, between 0.10 and 0.19% of total hen-days were exposed to chlortetracycline. Only two water-soluble administrations were recorded during the entire study period, both involving lincomycin to pullet flocks for the treatment of necrotic enteritis. Overall, antimicrobial use in the U.S. layer industry was focused mainly on controlling necrotic enteritis in the pullets and treating E. coli-related disease in the laying hens.

Antimicrobials in Animal Agriculture in the United States: A Multidisciplinary Overview of Regulation and Utilization to Foster Collaboration: On Behalf Of the Society of Infectious Diseases Pharmacists.

Given the complexity of antimicrobial resistance and the dire implications of misusing antimicrobials, it is imperative to identify accurate and meaningful ways to understand and communicate the realities, challenges, and opportunities associated with antimicrobial utilization and measurement in all sectors, including in animal agriculture. The objectives of this article are to (i) describe how antimicrobials are regulated and used in US animal agriculture and (ii) highlight realities, challenges, and opportunities to foster multidisciplinary understanding of the common goal of responsible antimicrobial use. Recognition of the realities of medicine, practice, and policy in the agricultural setting is critical to identify realistic opportunities for improvement and collaboration.

Improving farm-level antimicrobial stewardship benchmarks by reporting antimicrobial use within the context of both the magnitude of disease pressure and the outcome of therapy.

This manuscript explores a method of benchmarking antimicrobial use within the context of farm level therapeutic incidence (a proxy for disease incidence), and the outcome of that therapy. This is reported both within the same farm over time (2016-2019), as well as evaluated across participating farms. Reporting antimicrobial use in this format addresses multiple primary questions necessary for evaluating on farm antimicrobial stewardship: How much disease is recorded? How much antimicrobial use is recorded? How often are antimicrobials included in therapy for each disease? What is the outcome of therapy? The three primary metrics reported are: therapeutic events per 100 cow years (TE/100CY), antimicrobial regimens per 100 cow years (REG/100CY), and the percent therapeutic success (% Success). Success was defined as: the cow remained in the herd and had no further TE recorded within 30 days of the end of the TE being evaluated. These measures identify opportunities for change on an individual farm, such as improvement in disease prevention, or a change in choices about when to include an antimicrobial in the treatment protocol. Therapeutic outcomes provide additional context, in some instances demonstrating differences in recording practices and case definitions, while in other cases serving to safeguard animal welfare as efforts are made to decrease antimicrobial use in the future. Although developed for farm level reporting, the metrics may also be more broadly summarized to meet future reporting requirements for marketing chain or national level antimicrobial use reports. The process outlined here serves as a prototype to be considered when developing antimicrobial use reporting systems where farm level antimicrobial stewardship is the primary objective.

Refining the definition of the avian pathogenic Escherichia coli (APEC) pathotype through inclusion of high-risk clonal groups.

Colibacillosis in poultry is a unique disease manifestation of Escherichia coli in the animal world, as one of the primary routes of entry is via the respiratory tract of birds. Because of this, a novel extraintestinal pathogenic E. coli (ExPEC) subpathotype coined avian pathogenic E. coli (or APEC) has been described. Like other ExPEC, this pathotype has been challenging to clearly define, and in the case of APEC, its role as an opportunistic pathogen has further complicated these challenges. Using 3,479 temporally matched genomes of poultry-source isolates, we show that the APEC plasmid, previously considered a defining trait of APEC, is highly prevalent in clinical isolates from diseased turkeys. However, the plasmid is also quite prevalent among cecal E. coli isolates from healthy birds, including both turkeys and broilers. In contrast, we identify distinct differences in clonal backgrounds of turkey clinical versus cecal strains, with a subset of sequence types (STs) dominating the clinical landscape (ST23, ST117, ST131, ST355, and ST428), which are rare within the cecal landscape. Because the same clinical STs have also dominated the broiler landscape, we performed lethality assays using strains from dominant STs from clinical or cecal landscapes in embryonated turkey and chicken eggs. We show that, irrespective of plasmid carriage, dominant clinical STs are significantly more virulent than dominant cecal STs. We present a revised APEC screening tool that incorporates APEC plasmid carriage plus markers for dominant clinical STs. This revised APEC pathotyping tool improves the ability to identify high-risk APEC clones within poultry production systems, and identifies STs of interest for mitigation targets.

Longitudinal Changes in Campylobacter and the Litter Microbiome throughout the Broiler Production Cycle.

Broiler chickens are an important source of Campylobacter to humans and become colonized on the farm, but the role of the litter in the ecology of Campylobacter is still not clear. The aim of this study was to examine the relationship between Campylobacter and the changes in the litter microbiome throughout the broiler production cycle. Twenty-six commercial broiler flocks representing two production types (small and big broilers) were followed from 1 to 2 weeks after placement to the end of the production cycle. Composite litter samples from the broiler chicken house were collected weekly. Litter DNA was extracted and used for Campylobacter jejuni and Campylobacter coli qPCR as well as for 16S rRNA gene V4 region sequencing. Campylobacter jejuni concentration in litter significantly differed by production type and flock age. Campylobacter jejuni concentration in litter from big broilers was 2.4 log10 units higher, on average, than that of small broilers at 3 weeks of age. Sixteen amplicon sequence variants (ASVs) differentially abundant over time were detected in both production types. A negative correlation of Campylobacter with Bogoriella and Pseudogracilibacillus was observed in the litter microbiome network at 6 weeks of flock age. Dynamic Bayesian networks provided evidence of negative associations between Campylobacter and two bacterial genera, Ornithinibacillus and Oceanobacillus, at 2 and 4 weeks of flock age, respectively. In conclusion, dynamic associations between Campylobacter and the litter microbiome were observed during grow-out, suggesting a potential role of the litter microbiome in the ecology of Campylobacter colonization and persistence on farm. IMPORTANCE This study interrogated the longitudinal association between Campylobacter and broiler litter microbiome in commercial broiler flocks. The results of this investigation highlighted differences in Campylobacter dynamics in the litter throughout the broiler production cycle and between small and big broilers. Besides documenting the changing nature of the microbial networks in broiler litter during grow-out, we detected bacterial genera (Oceanobacillus and Ornithinibacillus) negatively associated with Campylobacter abundance and concentration in litter via the Bayesian network framework. These bacteria should be investigated as possible antagonists to Campylobacter colonization of the broiler environment.

Occurrence and potential transmission of extended-spectrum beta-lactamase-producing extraintestinal pathogenic and enteropathogenic Escherichia coli in domestic dog faeces from Minnesota.

Interactions between humans and pets are increasingly valued in western countries, leading to more extensive contact between humans and their pets within households. Although the magnitude of the risk of transfer of Escherichia coli between humans and their companion animals is undefined, that such transmission occurs has been established and warrants attention. This study examined 186 fresh faecal samples from companion dogs visiting 22 municipal dog parks in the Minneapolis/Saint Paul metropolitan area, Minnesota, USA. Samples were processed to isolate 3rd-generation cephalosporin-resistant E. coli, which were further characterized using PCR-based virulence genotyping, antimicrobial susceptibility profiling and whole-genome sequencing. Of the 186 faecal samples, 29% yielded cephalosporin-resistant E. coli, and 2.2% yielded extended-spectrum beta-lactamase producers. Co-resistance to sulfonamides was typical (77.3% of isolates), and multidrug resistance (i.e. to ≥3 antimicrobial classes), including to combinations of tetracyclines, phenicols, quinolones and aminoglycosides, was substantial (18.9% of isolates). Identified beta-lactamase genes included blaCMY-2 , blaTEM-1B , blaTEM-1 , blaCTX-M-24 , blaCTX-M-15 and blaOXA-1 . Genome sequencing of 14 isolates identified genes typical of extraintestinal pathogenic E. coli or enteropathogenic E. coli. In three instances, closely related isolates were recovered from different dogs, within either the same park-suggesting transfer of E. coli between dogs within the park-or different parks-suggesting that dogs may be pre-disposed to carry certain E. coli types, such as those from serogroups O4, O71 and O157. This study adds to the existing evidence that companion dogs can harbour and share antimicrobial-resistant E. coli with presumed intestinal or extraintestinal pathogenic potential.

Assessment of Diversity of Antimicrobial Resistance Phenotypes and Genotypes of Mannheimia haemolytica Isolates From Bovine Nasopharyngeal Swabs.

The threat of bovine respiratory disease (BRD) for cattle operations is exacerbated by increasing prevalence of antimicrobial resistance (AMR) in Mannheimia haemolytica, a leading cause of BRD. Characterization of AMR in M. haemolytica by culture and susceptibility testing is complicated by uncertainty regarding the number of colonies that must be selected to accurately characterize AMR phenotypes (antibiograms) and genotypes in a culture. The study objective was to assess phenotypic and genotypic diversity of M. haemolytica isolates on nasopharyngeal swabs (NPS) from 28 cattle at risk for BRD or with BRD. NPS were swabbed onto five consecutive blood agar plates; after incubation up to 20 M. haemolytica colonies were selected per plate (up to 100 colonies per NPS). Phenotype was determined by measuring minimum inhibitory concentrations (MIC) for 11 antimicrobials and classifying isolates as resistant or not. Genotype was indirectly determined by matrix-assisted laser desorption/ionization time of flight mass spectroscopy (MALDI-TOF MS). NPS from 11 of 28 cattle yielded at least one M. haemolytica isolate; median (range) of isolates per NPS was 48 (1-94). NPS from seven cattle yielded one phenotype, 3 NPS yielded two, and 1 NPS yielded three; however, within a sample all phenotypic differences were due to only one MIC dilution. On each NPS all M. haemolytica isolated were the same genotype; genotype 1 was isolated from three NPS and genotype two was isolated from eight. Diversity of M. haemolytica on bovine NPS was limited, suggesting that selection of few colonies might adequately identify relevant phenotypes and genotypes.

Identifying the spatiotemporal vulnerability of soils to antimicrobial contamination through land application of animal manure in Minnesota, United States.

Antimicrobials may reach the soil environment from a variety of sources and pathways, including land application of human biosolids and animal manure. Once in soil, antimicrobials can affect the abundance and activity of soil microorganisms and exert selection pressures that enhance the emergence and spread of antimicrobial resistance (AMR). To mitigate the spread of AMR it is important to understand the spatial and temporal interactions between antimicrobials and soil. The goal of this study was to assess the vulnerability of Minnesota (U.S.) soil to contamination with specific antimicrobial compounds at temperatures experienced throughout the year. Soil contamination potential was estimated based upon specific antimicrobial drug binding and permanence, and average monthly temperature. Minnesota soil vulnerability was estimated by incorporating spatially explicit soil contamination potential, land cover type, and livestock density. Assessment of antimicrobials used in livestock production showed that soils are most vulnerable to antimicrobial contamination in southwestern Minnesota, to enrofloxacin, chlortetracycline, and oxytetracycline, and in the months of April and October. While the assessment herein was not based on actual on-farm antimicrobial use data and subsequent excretion of antimicrobial metabolites into the environment, this study provides an overview of the spatial and temporal potential for Minnesota soil to be contaminated by several antimicrobial drugs and demonstrates how specific vulnerability assessments might be conducted for geographic areas with known exposure (e.g., cropland fertilized with livestock manure and/or human biosolids). Such assessments might be used to identify best practices for mitigating antimicrobial exposure to soils and guide additional research to understand the role of environmental antimicrobial contamination in the problem of AMR.

The association of multiple metrics for evaluating antimicrobial use in U.S. beef feedyards.

In order to accurately portray antimicrobial use in food animals, the need for standardized metrics, and an understanding of the characteristics of different metrics, has long been recognized. Fourteen U.S. feedyards were used to evaluate the effects of using centralized constants such as defined daily dose (DDD) and defined course dose (DCD) applied to the weight of medically important antimicrobials by class (mg) as opposed to using electronic individual animal treatment records and lot level in-feed antimicrobial records obtained from the same population. Three numerators were calculated directly from recorded data for each drug product: the number of antimicrobial regimens associated with indication (Reg), milligrams of drug administered per regimen (mg), and calendar days of administration for each regimen (CDoA). There were four use indications to which numerators were assigned: liver abscess control (LAC), bovine respiratory disease (BRD), lameness (lame), or all other indications combined (other). Three denominators were also calculated directly from the data, these being the number of days animals were present (head days), number of cattle received (head in), and kilograms of live weight sold (kg-LW). Numerators and denominators were calculated at the lot level. The use of DDD or DCD was explored to determine how their use would affect interpretation of comparisons between lots or feedyards. At the lot level across both study years, the lot estimate of nDDD differed from the CDoA value by >25% in 49.2% of the lots. The number of Defined Course Doses (nDCD) was then compared to the number of Regimens (Reg). Comparing nDCD to Reg at the lot level across both study years, the lot estimate of nDCD differed from the Reg value by >25% in 46.4% of lots. Both year and metric were also shown to affect numerical feedyard ranking by antimicrobial use according to seven different metrics. The analysis reported here adds to the body of literature reporting substantial effects of metric choice on the conclusions drawn from comparing antimicrobial use across multiple production sites.