Impact of florfenicol dosing regimen on the phenotypic and genotypic resistance of enteric bacteria in steers.

The food animal sector's use of antimicrobials is heavily critiqued for its role in allowing resistance to develop against critically important antimicrobials in human health. The WHO recommends using lower tier antimicrobials such as florfenicol for disease treatment. The primary objective of this study was to assess the differences in resistance profiles of enteric microbes following administration of florfenicol to steers using both FDA-approved dosing regimens and two different detection methods. Our hypothesis was that we would identify an increased prevalence of resistance in the steers administered the repeated, lower dose of florfenicol; additionally, we hypothesized resistance profiles would be similar between both detection methods. Twelve steers were administered either two intramuscular (20 mg/kg q 48 h; n = 6) or a single subcutaneous dose (40 mg/kg, n = 6). Fecal samples were collected for 38 days, and E. coli and Enterococcus were isolated and tested for resistance. Fecal samples were submitted for metagenomic sequencing analysis. Metagenomics revealed genes conferring resistance to aminoglycosides as the most abundant drug class. Most multidrug resistance genes contained phenicols. The genotypic and phenotypic patterns of resistance were not similar between drug classes. Observed increases in resistant isolates and relative abundance of resistance genes peaked after drug administration and returned to baseline by the end of the sampling period. The use of a "lower tier" antimicrobial, such as florfenicol, may cause an increased amount of resistance to critically important antimicrobials for a brief period, but these changes largely resolve by the end of the drug withdrawal period.

Flunixin meglumine tissue residues after intravenous administration in goats.

Background: Flunixin is commonly used in goats in an extra-label manner, indicating a significant need to determine withdrawal intervals for edible tissues. Objective: The objectives of the present study were to investigate the depletion of flunixin meglumine in various goat tissues, including the liver, kidney, fat, and muscle. Methods: Twenty Boer goats were enrolled and administered an intravenous dose (2.2 mg/kg) of flunixin meglumine. Five animals were randomly euthanized at 24, 48, 72, or 96 h following dosing. All samples were analyzed via ultra-performance liquid chromatography coupled with mass spectrometry. Results: The concentration of flunixin in all tissues declined rapidly, with the highest mean concentrations quantified in the kidney (0.137 ± 0.062 µg/g) and liver (0.077 ± 0.029 µg/g) tissues at 24 h. Conclusion: Since any detection of flunixin residues at slaughter found in goat tissues is considered a violative residue, a conservative withdrawal interval of 17 days was calculated to ensure levels of flunixin fell below the regulatory limits of detection in liver, kidney, and muscle tissues.

Comparison of the Intestinal Pharmacokinetics of Two Different Florfenicol Dosing Regimens and Its Impact on the Prevalence and Phenotypic Resistance of E. coli and Enterococcus over Time.

In order to mitigate the food animal sector's role in the growing threat of antimicrobial resistance (AMR), the World Health Organization (WHO) suggests the use of lower tier antimicrobials, such as florfenicol. Florfenicol has two dosing schemes used to treat primarily bovine respiratory disease. In this study, the objective was to characterize the plasma and gastrointestinal pharmacokinetics of each dosing regimen and assess the effect of these dosing regimens on the prevalence of resistant indicator bacteria over time. Twelve steers underwent abdominal surgery to facilitate the placement of ultrafiltration probes within the lumen of the ileum and colon, as well as placement of an interstitial probe. Following surgery, cattle were dosed with either 20 mg/kg IM every 48 h of florfenicol given twice (n = 6) or a single, subcutaneous dose (40 mg/kg, n = 6). Plasma, interstitial fluid, gastrointestinal ultrafiltrate, and feces were collected. Pharmacokinetic analysis demonstrated high penetration of florfenicol within the gastrointestinal tract for both the high and low dose group (300%, 97%, respectively). There was no significant difference noted between dosing groups in proportion or persistence of phenotypically resistant bacterial isolates; however, the percent of resistant isolates was high throughout the study period. The recommendation for the use of a lower tier antimicrobial, such as florfenicol, may allow for the persistence of co-resistance for antibiotics of high regulatory concern.

Retrospective study on the use of lidocaine constant rate infusions for the treatment of ileus in ruminants and camelids.

Limited knowledge exists regarding the use of lidocaine as a prokinetic in ruminants and camelids to treat gastrointestinal ileus. In this retrospective study, ruminant and camelid cases diagnosed with ileus and treated with a lidocaine constant rate of infusion were assessed for adverse reactions and medical outcomes. A review of medical records was performed to identify cases in which lidocaine was administered as a prokinetic. Ten cases were identified consisting of 8 cattle, 1 goat, and 1 alpaca. Nine animals improved with a lidocaine treatment. No adverse effects were reported during lidocaine administration. Nine animals were discharged, and 1 was euthanized.

Mycobacterial Cell Wall Stimulant in the Treatment of Squamous Cell Carcinoma: A Case Series Regarding Treatment in Equine, Bovine and Caprine Patients.

Squamous cell carcinoma (SCC) is a common dermatological neoplasia found in large animal species. Treatment options, such as surgery and cryotherapy may be difficult or not feasible. Alternative therapies, such as immunomodulating drugs, can potentially be used for companion large animals. The hypothesis of the following retrospective study is: following multiple intravenous and intralesional injections of a mycobacterial cell wall stimulant (MCW) regression of SCC in equine, bovine and caprine patients will be observed. In this observational-retrospective case series, patients included are 2 bovine, 2 caprine and 3 equine patients. The medical records at two different teaching veterinary hospitals were searched for cases with a positive histopathological diagnosis of squamous cell carcinoma that were subsequently treated with MCW, as either the sole therapy, or in conjunction with other therapies. Seven cases were included in this retrospective study. The median duration of therapy was 56.5 days, with 3 of the 7 patients being euthanized. Significant complications were seen in 3/7 patients. Repeated injections of a MCW may lead to reduction in lesion size of SCC in some cases, but long-term resolution is unlikely and the risk of significant complications is high; due to limited sample size and the variety in species, it is difficult to conclude if MCW is an effective therapy for SCC.

Surgical ligation of patent ductus arteriosus in a dorper sheep.

OBJECTIVE: To report the diagnosis and treatment of a companion dorper wether with patent ductus arteriosus (PDA). STUDY DESIGN: Case report. ANIMAL: An 8-month-old dorper wether presented to its primary care veterinarian for a persistent cough and was referred for suspected heart failure on the basis of physical examination and thoracic radiography. A PDA was diagnosed on echocardiography. METHODS: The sheep underwent cardiac catheterization and angiogram to measure pulmonary arterial and right ventricular (RV) pressures, identify the morphology of the PDA, and determine whether an intravascular occlusion of the PDA was feasible. Pulmonary artery pressure was 84/53 mm Hg (mean = 66), and RV pressures were 79/5 mm Hg (mean = 45); these were consistent with pulmonary hypertension. The size and shape of the PDA precluded vascular occlusion. Instead, the PDA was ligate through a left fourth intercostal approach. RESULTS: The sheep improved clinically after surgery. The PDA seemed closed on echocardiogram 3 days after surgery. Measurement of postoperative fractional shortening was consistent with decreased left ventricular systolic function that had resolved according to follow-up echocardiography. CONCLUSION: We report the first known diagnostic evaluation and successful treatment of naturally occurring PDA in a companion sheep. CLINICAL SIGNIFICANCE: For economically valuable small ruminants, radiographs, echocardiography and cardiac catheterization can be used to diagnose and plan surgical treatment of PDAs, with a potential for a good long-term outcome.

Short communication: Apparent efficiency of colostral immunoglobulin G absorption in Holstein heifers.

Adequate absorption of bovine colostrum correlates with improved neonatal health. The apparent efficiency of absorption (AEA) of immunoglobulins can be measured using a mathematical equation based on serum and colostral IgG concentration levels, as well as calf body weight and the volume of colostrum being fed. Although commonly measured in research projects, little information is available on the normal AEA across a large group of healthy calves on multiple farms. The purpose of this study was to observe how contributing factors (volume of feeding, birth weight, and time of feeding) can alter AEA and establish a reference range for AEA in healthy calves. Study subjects were 100 Holstein heifer calves from 5 different dairies in North Carolina and Colorado. After a normal calving, the heifer received either 4 or 5.6 L of colostrum within 4 h of birth, an aliquot of the fed colostrum was saved, and a blood sample was collected between 24 and 36 h after birth. Birth weights were measured using the same weight tape on each farm. Radial immunodiffusion assay was performed to obtain IgG concentrations in the colostrum and serum samples. From this data, the AEA was calculated. The AEA ranged from 7.7 to 59.9% with mean of 28.1 ± 9.5% and median of 27.5%. The AEA of 69% of the calves fell between 21 and 40%. The AEA varied widely between calves, even when feeding was standardized. Results suggest that serum IgG concentration may potentially be increased by feeding increased volumes of colostrum or genetic selection, given the wide range of AEA values obtained.

Androgen receptor and histone lysine demethylases in ovine placenta.

Sex steroid hormones regulate developmental programming in many tissues, including programming gene expression during prenatal development. While estradiol is known to regulate placentation, little is known about the role of testosterone and androgen signaling in placental development despite the fact that testosterone rises in maternal circulation during pregnancy and in placenta-induced pregnancy disorders. We investigated the role of testosterone in placental gene expression, and focused on androgen receptor (AR). Prenatal androgenization decreased global DNA methylation in gestational day 90 placentomes, and increased placental expression of AR as well as genes involved in epigenetic regulation, angiogenesis, and growth. As AR complexes with histone lysine demethylases (KDMs) to regulate AR target genes in human cancers, we also investigated if the same mechanism is present in the ovine placenta. AR co-immunoprecipitated with KDM1A and KDM4D in sheep placentomes, and AR-KDM1A complexes were recruited to a half-site for androgen response element (ARE) in the promoter region of VEGFA. Androgenized ewes also had increased cotyledonary VEGFA. Finally, in human first trimester placental samples KDM1A and KDM4D immunolocalized to the syncytiotrophoblast, with nuclear KDM1A and KDM4D immunostaining also present in the villous stroma. In conclusion, placental androgen signaling, possibly through AR-KDM complex recruitment to AREs, regulates placental VEGFA expression. AR and KDMs are also present in first trimester human placenta. Androgens appear to be an important regulator of trophoblast differentiation and placental development, and aberrant androgen signaling may contribute to the development of placental disorders.

Identification of microRNAs in exosomes isolated from serum and umbilical cord blood, as well as placentomes of gestational day 90 pregnant sheep.

Despite reports that circulating levels of maternal serum exosomes increase during pregnancy and that placenta-specific microRNAs (miRNAs) have been identified in humans, little is known about exosomes and miRNAs during pregnancy in agriculture animals. In this study, we characterized the expression of 94 miRNAs in ovine placentomes at gestation day (GD) 90 by real-time PCR, and then investigated the presence of these miRNAs in exosome samples isolated from maternal jugular blood in non-pregnant ewes and at GD30 and GD90 and in umbilical blood collected at GD90. In maternal jugular exosome samples, 13 miRNAs were present in lower and 12 miRNAs were present in higher amounts at GD90 compared to non-pregnant (GD0) or GD30. Additionally, 12 miRNAs were present in higher amounts in umbilical venous exosomes compared to umbilical arterial exosomes; only miR-132 was lower in exosomes isolated from umbilical venous blood than from umbilical arterial blood. In placentome samples, miR-34c and miR135a abundance was higher in cotyledon tissue than in caruncle, while miR-183 and miR-379 amounts were higher in caruncle than cotyledon tissue. Only miR-379 was differentially expressed in all serum exosomes and placentome samples. Pathway analysis predicted that differentially expressed maternal serum exosomal miRNAs target Cellular Growth and Proliferation and Organ Development pathways, while umbilical serum exosomal and placentomes miRNAs were predicted to target cellular development and organismal/embryonic development.