Twenty-four rams inoculated with Brucella ovis by conjunctival and preputial routes were treated with a long-acting oxytetracycline alone or in combination with dihydrostreptomycin sulfate. The combined treatment eliminated Brucella ovis from 11 of 12 (91.6%) treated rams. Only 4 of 12 (33.3%) rams treated with oxytetracycline alone were bacteriologically negative. Neither treatment resolved clinical epididymitis in 2 rams affected before treatment. Many rams had pathologic lesions in the epididymis and ampullae, which limited the efficacy of antibiotic treatment.

Oxytetracycline (OTC) pharmacokinetic values in plasma and bile were ascertained after IV administration of the drug. At 6 hours after administration of 1 mg of OTC/kg of body weight, 2.15% of the dose was found in the bile and 37.6% was found in the urine. At 2 hours after administration, the peak bile-to-plasma OTC concentration ratio was 60:1. Bioavailability of OTC was 47.6% when it was administered orally to fasted turkeys and was 9.4% when administered to fed turkeys.

Tissue specimens from muscle, liver, kidney, and injection sites were collected, and serum was obtained from 3 calves euthanatized on each of posttreatment days 5 and 22. Calves were treated with 6.7, 13.4, or 20 mg of oxytetracycline (OTC)/kg of body weight, IM, once daily for 3 days; these dosages are 1, 2, and 3 times the label dose, respectively. One control calf was euthanatized on each of posttreatment days 5 and 22. In treated male calves killed 2 days after the last injection, OTC residues were detected in all tissues and serum, using high-performance liquid chromatography. Tissues from all injection sites also were considered positive for antimicrobial residues, using swab test on premises (STOP), microbial inhibition test (MIT), and thin-layer chromatography-biautography (TLCB) test. Kidney tissues from a calf given 13.4 mg of OTC/kg and kidney and liver tissues from a calf given 20 mg of OTC/kg also were considered positive, using the MIT and TLCB. Results of the STOP only were considered positive for the liver and kidney of a calf given 20 mg of OTC/kg, but substitution of Saskatoon antibiotic medium-3 for the original medium (antibiotic medium-5) allowed the STOP to detect residues in these tissues from all treated calves. In female calves killed 19 days after the last injection, the STOP, MIT, and TLCB procedures revealed positive results for tissues from some injection sites, but revealed negative results for other tissues. High-performance liquid chromatographic analyses detected OTC in tissues from injection sites from all treated calves, in muscle and liver from a calf given 20 mg of OTC/kg, and in kidneys from calves given 13.4 or 20 mg of OTC/kg. The STOP, MIT, and TLCB procedures lacked the sensitivity of high-performance liquid chromatography for detection of OTC residues.

Introduction: The article presents a rapid and simple analytical procedure for determination of four tetracyclines (oxytetracycline, tetracycline, chlortetracycline, and doxycycline) in animal medicated feedingstuffs. Material and Methods: Two-gramme samples were extracted by a Na2EDTA-McIlvaine buffer (pH 4)/methanol mixtures (40/60, v/v). The determination was achieved by liquid chromatography using a Zorbax Eclipse XDB C18 analytical column with mass spectrometer detection (LC-MS). Results: Recoveries of the antibiotics from spiked feed samples ranged from 78.2% to 113.5%. The LOD and LOQ for tetracyclines in feeds ranged from 2.8 to 4.2 and from 4.3 to 5.7 mg/kg, respectively. Conclusion: The method was successfully validated and proved to be efficient, precise, and useful for quantification of tetracyclines in medicated feedingstuffs.

Introduction: The article presents a rapid and simple analytical procedure for determination of four tetracyclines (oxytetracycline, tetracycline, chlortetracycline, and doxycycline) in animal medicated feedingstuffs. Material and Methods: Two-gramme samples were extracted by a Na₂EDTA-McIlvaine buffer (pH 4)/methanol mixtures (40/60, v/v). The determination was achieved by liquid chromatography using a Zorbax Eclipse XDB C18 analytical column with mass spectrometer detection (LC-MS). Results: Recoveries of the antibiotics from spiked feed samples ranged from 78.2% to 113.5%. The LOD and LOQ for tetracyclines in feeds ranged from 2.8 to 4.2 and from 4.3 to 5.7 mg/kg, respectively. Conclusion: The method was successfully validated and proved to be efficient, precise, and useful for quantification of tetracyclines in medicated feedingstuffs.

Introduction: The study sought to characterise antimicrobial resistance among coagulase-negative Staphylococcus (CNS) species recovered from broiler chickens and turkeys in Poland including the presence of 12 antimicrobial resistance genes and five classical genes of staphylococcal enterotoxins. Material and Methods: A panel of 11 antimicrobial disks evaluated the phenotypic sensitivity of the tested strains to antibiotics. Five multiplex PCR assays were performed using primer pairs for specific detection of antibiotic resistance genes and staphylococcal enterotoxin A to E genes. Results: Selected antimicrobial agent susceptibility testing revealed 100% of such in in vitro conditions to cefoxitin among strains of Staphylococcus sciuri and S. chromogenes. The blaZ (for ß-lactam) and mecA (for methicillin resistance) genes were in 58.3% and 27.5% of strains, respectively. Among genes resistant to tetracyclines, tetK was most frequent. Fewer (CNS) strains showed genes resistant to macrolides, lincosamides, and florfenicol/chloramphenicol. Multiplex PCR for classical enterotoxins (A-E) detected the see gene in two S. hominis strains, while the seb gene producing enterotoxin B was found in one strain of S. epidermidis. Conclusion: CNS strains of Staphylococcus isolated from poultry were either phenotypically or genotypically multidrug resistant. Testing for the presence of the five classical enterotoxin genes showed that CNS strains, as in the case of S. aureus strains, can be a source of food intoxications.

The occurrence of veterinary drug residues in chicken meat originating from 320 small and medium scale chicken slaughterhouses in Peninsular Malaysia was determined. 637 chicken meat samples were examined for tetracycline (TCs), sulphonamide (SAs) and quinolone residues using a microbiological inhibition test and was further confirmed using liquid chromatography mass spectrometry (LCMS/MS). The presence of TC residues were confirmed in 10 (1.6%) samples, and 1 (0.2%)sample was confirmed in compliance to the established maximum residue limit (MRL) for residues of quinolone. A total of 6 (0.9%) samples were above the MRL for TC. The samples were from Pulau Pinang, Terengganu and Kelantan. Among those tested in compliance, the main analytes found for TC and quinolone werechlortetracyclines (CTC), enrofloxacin and mixture of chlortetracycline (CTC) and oxytetracycline (OTC). No samples were found to contain sulfonamides residues.

A 2 X 2 crossover design trial was conducted in gilts to determine the bioavailability and pharmacokinectics of tetracycline hydrochloride. The bioavailability of tretracycline hydrochloride administered orally to fasted gilts was approximately 23%. After intravascular administration, the disposition kinetics of tetracycline in plasma were best described by a triexponential equation. The drug had a rapid distribution phase followed by a relatively slow elimination phase, with half-life of 16 hours. Its large volume of distribution (4.5 +/- 1.06 L/kg) suggested that tetracycline is distributed widely in swine tissues. Total body clearance was 0.185 +/- 0.24 L/kg/h. Other pharamacokinectic variables were estimated. In a second trial, 3 gilts were fed a ration containing 0.55 g of tetracycline hydrochloride/kg of feed. Resulting plasma concentration of tetracycline was determined at selected times during 96 hours after exposure to the medicated feed. Plasma drug concentration peaked (0.6 microgram/ml) at 72 hours after access to the medicated feed.

The use of antibiotics in livestock production in North America and possible association with elevated abundance of detectable antimicrobial resistance genes (ARG) is a growing concern. Real-time, quantitative PCR (RT-qPCR) was used to determine the relative abundance and diversity of ARG in fecal composite and catch basin samples from 4 beef feedlots in Alberta. Samples from a surrounding waterway and municipal wastewater treatment plants were also included to compare the ARG profile of urban environments and fresh water with that of feedlots. The relative abundance of 18 resistance genes across 5 antibiotic families including sulfonamides, tetracyclines, macrolides, fluoroquinolones, and β-lactams was examined. Sulfonamide, fluoroquinolone, and β-lactam resistance genes predominated in wastewater treatment samples, while tetracycline resistance genes predominated in cattle fecal composite samples. These results reflect the types of antibiotic that are used in cattle versus humans, but other factors such as co-selection of ARG and variation in the composition of bacterial communities associated with these samples may also play a role.

Neospora caninum causes serious disease in dogs, and it, or a similar parasite, is a major cause of abortion in cattle. Little is known about the susceptibility of this protozoan to antimicrobial agents. We studied several antimicrobial agents to determine which classes might have activity against this parasite. We also determined whether activity of such agents was coccidiocidal or coccidiostatic. A 2-day of treatment, monoclonal antibody-based enzyme immunoassay and a 5-day of treatment, cell culture flask (CCF), lesion-based assay were developed to examine the ability of test agents to inhibit tachyzoite multiplication. Seven sulfonamides were examined, with the following activities observed: sulfathiazole greater than or equal to sulfamethoxazole > sulfadiazine > sulfaquinoxaline greater than or equal to sulfamethazine > sulfadimethoxine > sulfamerazine. Dapsone, a sulfone, had little activity. Six dihydrofolate reductase/thymidylate synthase inhibitors were examined, with the following activities observed: piritrexim > pyrimethamine > ormetoprim > trimethoprim = diaveridine > methotrexate. Six ionophorous antibiotics were examined; lasalocid, maduramicin, monensin, narasin, and salinomycin had equivalent activities, but alborixin was toxic for host cells at the lowest concentration examined. Three macrolide antibiotics--azithromycin, clarithromycin, and erythromycin--were examined and had equivalent activities. Two tetracycline antibiotics, doxycycline and minocycline, were examined and had equivalent activities. Three lincosamide antibiotics were examined, with the following activities observed: clindamycin hydrochloride > clindamycin phosphate > lincomycin hydrochloride. Pentamidine and 6 of its analogs were examined, and only hexamidine and 1,4-Di[4-(2-imidazolinyl)-2-methoxy-phenoxylbutane had activity. Eight miscellaneous antiprotozoal agents were examined for activity. Amprolium, metronidazole, paromomycin, and roxarsone had little activity. Arprinocid, diclazuril, nitrofurazone, and robenidine had good activity. Eleven agents were examined in both assays, whereas 32 agents were examined in the CCF assay only. The enzyme immunoassay and CCF assay provided similar results for agents that rapidly killed tachyzoites. However, agents that inhibited development, but were not rapidly fatal for tachyzoites, had better activity in the CCF assay. Of the classes of agents examined, the dihydrofolate reductase/thymidylate synthase inhibitors, 2 of the 6 pentamidine analogs, and the ionophores were coccidiocidal and the sulfonamides, macrolides, tetracyclines, and lincosamides were coccidiostatic. Of the miscellaneous agents examined, arprinocid, nitrofurazone, and robenidine were coccidiocidal and diclazuril was coccidiostatic.