Oxytetracycline In Milk Research Articles

Short communication: Determination of withdrawal time for oxytetracycline in different types of goats for milk consumption

Antibiotics are widely used in animal husbandry and the presence of antibiotics in milk is a health hazard. The objective of this study was to determine residual amounts of oxytetracycline in fresh, aged, and pasteurized milk of 3 breeds of goats using HPLC analysis. It was also essential to determine the safe withdrawal period of oxytetracycline in lactating goats. The quantitative results obtained using the HPLC system were compared with the tolerance limit of oxytetracycline in milk in the United States. Fifteen milking does, 5 Nubians, 5 Alpines, and 5 LaManchas were randomly selected from the milking herd at the International Goat Research Center at Prairie View A&M University. A simple sample preparation and isocratic HPLC method using ultraviolet detection was used for analysis of milk samples. The HPLC results indicated that the withdrawal period of oxytetracycline in treated Alpine does was 82h (7 milking), whereas for Nubian does the period was 58h (5 milking), and for LaManchas the period was 72h (6 milking) after drug administration. The overall withdrawal period for all the treated goats of 3 breeds was 72h. Although these results indicated that the depletion rate of this antibiotic was faster in goats than the reported data for cows, the 96-h withdrawal period that is currently used for lactating cows is still necessary for these 3 breeds of goats. Additionally, our results indicated that oxytetracycline is not stable in goat milk at refrigeration temperature or during pasteurization and will decrease significantly.

Relationship between uterine pathology and depletion of oxytetracycline concentrations in plasma and milk after intrauterine infusion

Up to 90% of dairy cows develop bacterial contamination of the uterus during the first week after calving. Intrauterine treatment with antimicrobials is commonly practiced on dairy farms, even though studies demonstrating improved reproductive performance after treatment are lacking. Intrauterine infusion of antimicrobials can result in costly milk discard, and increases the risk for antimicrobial residue in bulk-tank milk intended for human consumption. Because there are currently no antimicrobials approved for intrauterine administration in cattle, the veterinarian is primarily responsible for ensuring that milk from treated cows is free from antimicrobial residues. Results of previous trials have indicated considerable variation in the depletion profile of drugs after intrauterine infusion. For this study, we hypothesized that the variability in the elimination of oxytetracycline in milk is associated with the extent of uterine pathology among cases.

An indirect competitive assay-based aptasensor for detection of oxytetracycline in milk

Oxytetracycline (OTC) is a common antibacterial agent used for the control of animal diseases. OTC abuse can seriously affect human health; therefore, we developed a biosensor using single-stranded DNA (ssDNA) aptamers for the detection of OTC. The binding probe aptamers for OTC were selected by a Systematic Evolution of Ligands by the exponential enrichment (SELEX) process and identified by the enzyme-linked aptamer assay (ELAA). Among the selected 5 aptamers, aptamer OTC3 showed the strongest affinity (Kd=4.7nM) and highest specificity for OTC compared to structurally similar antibiotics, tetracycline and chlortetracycline. OTC was detected using indirect competitive ELAA. The limit of detection and quantitation with aptamer OTC3 were 12.3 and 49.8µg/L, respectively, in milk and showed recovery rates of more than 90% in OTC-spiked milk. This biosensor method with high sensitivity and specificity based on indirect competitive ELAA can be applied to OTC detection in food products on-site because of the simplicity of detection.

Liquid chromatographic determination and depletion profile of oxytetracycline in milk after repeated intramuscular administration in sheep

A simple, rapid and specific ion-pair liquid chromatographic method for the routine determination of the marker residue of oxytetracycline in sheep milk, at levels as low as 20 μg/kg, has been developed. Milk samples were acidified and extracted with acetonitrile. The extracts were purified by treatment with ammonium sulphate and concentrated into diluted phosphoric acid. Separation was carried out isocratically on a Nucleosil C 18 column using a mobile phase that contained both positively and negatively charged pairing ions. The in-house validated method gave overall recoveries and overall relative standard deviations better than 86% and 4.6%, respectively. The method was successfully applied to study the depletion of oxytetracycline in sheep milk and to estimate the withdrawal period after intramuscular administration of a commercial oxytetracycline formulation.

Sample preparation followed by HPLC under harmless 100% aqueous conditions for determination of oxytetracycline in milk and eggs.

A simple and hazardous chemical-free method for the high-performance liquid chromatographic determination of oxytetracycline (OTC) residues in milk and eggs has been developed. Sample preparation consists in homogenization with an aqueous solution by means of a handheld ultrasonic homogenizer followed by centrifugal ultrafiltration. HPLC is performed with an isocratic aqueous mobile phase and a photodiode array detector. Average recoveries of OTC (0.05, 0.1, and 0.2 microg mL(-1) for milk; 0.1, 0.2, and 0.4 microg mL(-1) for eggs) were > or =84% with relative standard deviations of < or =2.3%. The total time required for the analysis of one sample and LOQs were <30 min and <0.1 microg mL(-1), respectively. In all the processes, no organic solvents or hazardous reagents were used.

Pharmacokinetics and residues in milk of oxytetra‐cyclines administered parenterally to dairy goats

To determine for two commercial preparations of oxytetracycline (OTC) the pharmacokinetic behaviour, the presence of detectable milk residues and the penetration in milk of OTC administered by intravenous (IV) (conventional formulation [CF]) and intramuscular (IM) routes (CF and long-acting [LA] formulations) in goats producing milk. The effects of these formulations on plasma activity values of creatine kinase (CK) and lactate dehydrogenase (LDH) were also determined as indicators of tissue damage. Five healthy lactating goats producing 1.5+/-0.5 L/d milk and weighing 56.0+/-4.8 kg were used. Single doses of OTC chlorhydrate (CF) were administered (20 mg OTC/kg) by IV (Trial 1 IV) and IM (Trial 1 IM) routes and OTC dehydrate (LA) by the IM route. The same goats were first given IV CF, then IM CF followed by IM LA with 3 weeks between each treatment. Blood and milk samples were taken. The quantification of OTC was performed by HPLC and the plasma activities of CK and LDH enzymes were determined by spectrophotometry. The presence of OTC residues in milk was determined by a commercial reagent. The plasma pharmacokinetic parameters were calculated using a two-compartment model. Estimates of kinetic variables following IV administration were: Vss= 400.0+/-120.0 mL/kg and CL= 110.0+/-14.0 (mL/h)/kg. The t(fi) for IV= 3.0+/-0.3 h; IM, CF = 10.5+/-2.1 h and IM, LA = 15.1+/-3.1 h. The concentration of OTC in milk at 48 h was: IV= 0.6+/-0.4; IM CF= 1.1+/-0.2 and at 72 h (IM LA)= 0.6+/-0.1 microg/mL and the penetration in milk of OTC was: IV= 70.0+/-18.0; IM CF= 79.0+/-14.0 and IM LA= 66.0+/-6.0%. The areas under the curve of CK and LDH activities in plasma were calculated by the trapezoidal method. Values of CK and LDH IM, LA were greater (P < 0.05) than those observed for IM, CF at 2 and 3 days after administration of the antibiotic. Finally, the bioavailability of OTC CF = 92.0+/-22.0 and LA= 78.0+/-23.0% was suitable for its usage by the IM route in lactating goats. Plasma concentration-time values of OTC administered parenterally in production dairy goats showed similar bioavailability for the two pharmaceutical preaprations. The presence of detectable residues in milk indicates that milk should not be used for human consumption for 2 and 3 days after administration of conventional and long-acting formulations, respectively. The increments in CK and LDH activities after the IM administration of LA are consistent with the presence of tissue damage provoked by the pharmaceutical preparations at the injection site.

Detection and quantification of tetracyclines by whole cell biosensors

Three different mini-Tn5 plasmids, containing a tetracycline-inducible promoter, Ptet and a regulatory gene, tetR, in operon fusions with a reporter gene system (lacZYA, luxCDABE or gfp), were constructed. These biosensor constructs responded to low levels of tetracyclines by producing beta-galactosidase, light or green fluorescent protein. They did so in a quantitative manner, thus enabling the quantification of tetracyclines in the immediate surroundings of the biosensor organism. All three constructs were transferred successfully to different gram-negative bacteria by conjugation. An Escherichia coli strain containing the Ptet-lac construct was used to determine oxytetracycline in milk as a demonstration of the application of these biosensors.

Detection and quantification of tetracyclines by whole cell biosensors

Three different mini-Tn 5 plasmids, containing a tetracycline-inducible promoter, P tet and a regulatory gene, tetR, in operon fusions with a reporter gene system ( lacZYA, luxCDABE or gfp), were constructed. These biosensor constructs responded to low levels of tetracyclines by producing β-galactosidase, light or green fluorescent protein. They did so in a quantitative manner, thus enabling the quantification of tetracyclines in the immediate surroundings of the biosensor organism. All three constructs were transferred successfully to different Gram-negative bacteria by conjugation. An Escherichia coli strain containing the P tet - lac construct was used to determine oxytetracycline in milk as a demonstration of the application of these biosensors.

Rapid liquid chromatographic determination of oxytetracycline in milk

A simple method for the determination of residual oxytetracycline (OTC) in milk by high-performance liquid chromatography (HPLC) was developed. The sample preparation could be made without complex extraction and clean-up procedures. A LiChrospher 100 RP-8 end-capped column and a mobile phase of acetonitrile-acetic acid-water (28:4:68, v/v/v) with a photo-diode array detector was used. The average recoveries from spiked OTC (0.1, 0.5 and 1.0 μg/ml) were in excess of 89.8% with coefficients of variation between 0.6 and 4.1%. The limit of detection was 0.05 μg/ml. The total time required for the analysis of one sample was below 10 min.

Improved procedures for the determination of oxytetracycline in milk, milk products; chicken muscle, liver; and eggs.

The procedures used to determine residues of anitibotics in many types of commodities, raw or processes are based upon the classical cylinder-plate diffusion techniques (1). Perhaps the most comprehensive summary of procedures for antibiotic residues are those described by the FDA (2). In general, this publication is a compendium of sensitive and reproducible methods for assaying antibiotic residues. The purpose of this manuscript is to report on the evaluation of improved procedures for determining oxytetracycline in milk and dairy products, chicken muscle tissue and livers, and eggs. The procedures used are based upon those developed for chlortetracycline in similar materials (3,4,5) and are compared to the procedures listed in the FDA compendium of methods and protocols.