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M D Apley

Publications and source records attributed to M D Apley.

12 recordsLinked to original sources
PubMed2006

Flow cytometric evaluation of selected antimicrobial efficacy for clearance of Anaplasma marginale in short-term erythrocyte cultures.

The tick-borne rickettsia, Anaplasma marginale, causes the economically important cattle disease anaplasmosis. Once infected, cattle remain lifelong carriers. Herein, we used flow cytometry to test the efficacy of three antimicrobials; oxytetracycline, imidocarb and enrofloxacin against Virginia (VGN) or Oklahoma (OK) A. marginale isolates in short-term erythrocyte cultures. Parasite viability was assessed using the vital dye hydroethidine (HE), which is detectable when living organisms convert HE to ethidium bromide. Viability of A. marginale in selected cultures was determined by subinoculation into susceptible calves. Data were analyzed by MANOVA, Tukey-Kramer honest significant difference and Wilcoxon rank sum tests. Receiver operating characteristic (ROC) analysis was used to correlate results with culture infectivity. Enrofloxacin inhibited A. marginale in a dose dependent manner. Surprisingly, higher concentrations of imidocarb were less effective than lower concentrations against A. marginale with significant differences (P < 0.05) observed between the two isolates. Oxytetracycline was the least active drug tested. Cultures infected with the OK isolate exposed to 4.0 microg/mL enrofloxacin and those of the VGN and OK isolates exposed to 1.0 microg/mL imidocarb were sterilized. This is the first in vitro study demonstrating the efficacy of enrofloxacin against A. marginale. Furthermore, these data indicate that flow cytometry is a useful assay for screening antimicrobials against A. marginale.

Anaplasma marginale↗
PubMed2003

The effects of danofloxacin and tilmicosin on neutrophil function and lung consolidation in beef heifer calves with induced Pasteurella (Mannheimia) haemolytica pneumonia.

Pneumonia caused by Pasteurella (Mannheimia) haemolytica was induced in weaned beef heifer calves, approximately 6 months of age. Calves were treated at 20 h after challenge with therapeutic doses of danofloxacin or tilmicosin. Peripheral blood neutrophils were collected at 3, 24 and 48 h after treatment. The ex vivo effects on neutrophil function, neutrophil apoptosis, and hematological parameters were examined, as was the effect on percentage lung consolidation. Neutrophil function assays included random migration under agarose, cytochrome C reduction, iodination, Staphylococcus aureus ingestion, chemotaxis, and antibody-dependent and antibody-independent cell-mediated cytotoxicity. Apoptosis was determined using a cell death detection kit. Killing was performed at 72 h after treatment. Statistical comparisons were made among the three groups of challenged-treated animals: saline, danofloxacin, and tilmicosin. Comparisons were also made between nonchallenged nontreated animals (NCH) and challenged saline-treated animals. There were no significant differences for any of the neutrophil function assays or neutrophil apoptosis among the challenged-treated groups. This suggests that danofloxacin and tilmicosin have no clinically significant effects on neutrophil function or apoptosis. There were also no significant differences in percentage lung consolidation among the challenged-treated groups. Significant differences were found between the NCH calves and the challenged saline-treated calves in several neutrophil assays, which were attributed to effects of P. haemolytica infection.

Animals↗
PubMed2003

Pharmacodynamics of isoflupredone acetate in an endotoxin-induced mastitis model.

The effect of intravenous administration of the steroidal drug isoflupredone acetate on lactating dairy cows with mastitis induced using gram-negative bacterial endotoxin was investigated. Cows were randomly assigned to one of four treatment groups: untreated controls, isoflupredone acetate only, mastitis only, and mastitis plus isoflupredone acetate. Isoflupredone acetate was given to treated groups at a dose of 20 mg intravenously, once. Mastitic cows receiving treatment were given isoflupredone acetate after the development of clinical signs. When compared with untreated mastitic controls, cows with endotoxin-induced mastitis treated with isoflupredone acetate did not exhibit measurable differences in heart rate, rectal temperature, rumen motility, or changes in mammary gland surface area in the 14 h following the administration of intramammary endotoxin. Healthy cows treated with isoflupredone acetate had a higher heart rate over the 14 h after drug administration than did untreated healthy controls. When compared with untreated mastitic controls, cows treated with isoflupredone acetate did not exhibit statistically significant differences in milk production following endotoxin-induced mastitis.

Animals↗
PubMed2001

Antimicrobial issues in bovine lameness.

This article reviews some of the issues surrounding antimicrobial use in treating diseases that cause lameness in cattle. The discussion includes sections on selection of an antimicrobial, regimen design, and medication of multiple animals. Pathogen susceptibility testing is covered, along with empiric selection of antimicrobials. Other issues covered include regional perfusion and topical application of antimicrobials, antimicrobials in footbaths and in feed, and withdrawal time estimates.

Animals↗
PubMed2000

Animal and human multidrug-resistant, cephalosporin-resistant salmonella isolates expressing a plasmid-mediated CMY-2 AmpC beta-lactamase.

Salmonella spp. are important food-borne pathogens that are demonstrating increasing antimicrobial resistance rates in isolates obtained from food animals and humans. In this study, 10 multidrug-resistant, cephalosporin-resistant Salmonella isolates from bovine, porcine, and human sources from a single geographic region were identified. All isolates demonstrated resistance to cephamycins and extended-spectrum cephalosporins as well as tetracycline, chloramphenicol, streptomycin, and sulfisoxazole. Molecular epidemiological analyses revealed eight distinct chromosomal DNA patterns, suggesting that clonal spread could not entirely explain the distribution of this antimicrobial resistance phenotype. However, all isolates encoded an AmpC-like beta-lactamase, CMY-2. Eight isolates contained a large nonconjugative plasmid that could transform Escherichia coli. Transformants coexpressed cephalosporin, tetracycline, chloramphenicol, streptomycin, and sulfisoxazole resistances. Plasmid DNA revealed highly related restriction fragments though plasmids appeared to have undergone some evolution over time. Multidrug-resistant, cephalosporin-resistant Salmonella spp. present significant therapeutic problems in animal and human health care and raise further questions about the association between antimicrobial resistance, antibiotic use in animals, and transfer of multidrug-resistant Salmonella spp. between animals and man.

Animals↗
PubMed1998

Feedlot therapeutics.

This article discusses therapeutic approaches to conditions commonly encountered in feedlots. Challenges discussed include bovine respiratory complex, tracheal edema, atypical interstitial pneumonia, footrot, toe abscesses, mycoplasma arthritis, cardiovascular disease, lactic acidosis, bloat, coccidiosis, central nervous system diseases, abscesses and cellulitis, pregnancy management and abortion, and ocular disease.

Abortion, Veterinary↗
PubMed1998

Clinical trial design in feedlots.

As mentioned at the outset, the ultimate test of a product or procedure must be under field conditions and is best obtained from controlled studies of field use. Economic justification for use is based on this information. Each producer places a different value on attributable benefits such as improved health or growth performance. These values also change with fluctuating market values of cattle and feed. This makes determining the cost-benefit ratio of any procedure or product a moving target. Addressing this issue requires the clinically relevant and statistically significant differences that practitioners should be able to generate if they follow the guidelines presented here. There already exists a number of unusable studies. We suggest that those interested in undertaking this challenge be uncompromising in their experimental design. To be reliable, studies must follow the recommendations outlined above. Without sound field trial design and execution which ensures that the information is reliable and statistical significance which ensures that the differences are real, clinical outcomes cannot be extrapolated to economic justification. Any other course leads to making less than optimal recommendations on product use because of a lack of clinically relevant information.

Animal Husbandry↗
PubMed1993

Lung tissue concentrations and plasma pharmacokinetics of danofloxacin in calves with acute pneumonia.

Plasma and lung tissue pharmacokinetics of danofloxacin in calves with naturally induced acute pneumonia were determined in 2 separate studies. A maximal pneumonic tissue concentration of 1.17 micrograms/g was achieved 1.8 hours after IM injection of 1.25 mg of danofloxacin/kg of body weight. Pneumonic tissue danofloxacin concentrations were 5.5 times greater than those in plasma at 1 and 2 hours after injection. Cranioventral pneumonic tissue had significantly decreased danofloxacin concentration, compared with that of grossly normal tissue from the caudodorsal part of the lungs at 2 of 6 sample times. After IV injection, the apparent steady-state volume of distribution was 3.44 +/- 1.13 L/kg, and the elimination half-life was 6.26 +/- 2.27 hours. Maximal plasma danofloxacin concentration of 0.25 micrograms/ml was detected 0.80 hour after IM injection. Bioavailability was 91%. Our findings indicated that a large percentage of danofloxacin is rapidly absorbed after IM administration to calves with acute pneumonia. Extensive tissue penetration was suggested by a high steady-state volume of distribution and was indicated by high concentrations in pneumonic tissue.

Animals↗
PubMed1993

Regional danofloxacin lung tissue concentrations and their relationship to regional pulmonary blood flow in consolidated and nonconsolidated bovine lung.

Six calves with areas of pulmonary consolidation attributable to bronchopneumonia, and 6 calves with no areas of consolidation were given i.v. injections of danofloxacin. This injection was followed approximately 55 minutes later by injection of 15-microns radio-labeled microspheres to measure regional pulmonary blood flow. Calves were euthanatized exactly 1 hour after the danofloxacin injection. Six samples for determination of danofloxacin concentration, each surrounded by 4 samples for determination of gamma emission counts, were taken from each lung. Additional samples focusing on the line of demarcation between consolidated and nonconsolidated tissue were taken from calves with pulmonary consolidation. Data from calves with no areas of pulmonary consolidation indicated that blood flow was significantly reduced in the caudodorsal position of the left lung and the caudodorsal and cranioventral positions of the right lungs. Danofloxacin concentrations in the cranioventral positions of the right and left lungs were significantly lower than those in the middle-dorsal positions. Differences in danofloxacin concentrations and blood flow were analyzed in consolidated and non-consolidated cranioventral and middle-ventral positions of the lungs from calves with pulmonary consolidation. Decreases in blood flow in consolidated lung tissue ranged from 83.3 to 91.7%. Danofloxacin concentrations in consolidated lung tissue were significantly reduced by 41% in the middle-ventral position of the left lung. The line of demarcation step study revealed a significant reduction of blood flow at 2 and 4 cm into consolidated lung tissue, with reductions of 84 and 88%, respectively. Danofloxacin concentration did not significantly decrease in consolidated tissue.

Animals↗