Fluorimetric determination of the active form of tetracycline, chloretetracycline and oxytetracycline in partially decomposed solutions

The content of tetracycline (1), chlortetracycline (2) and oxytetracycline (3) has been determined by use of the fluorimetric method in partially decomposed acqueous solutions of different pH values. The procedure consisted in the extraction of fluorescent calcium and 5.5-diethyl-barbituric acid complexes of 1 and 3 (with 2 calcium complex only) into an organic solvent. In the method, only complexes with undecomposed 1--3 show a strong fluorescence. Products of decomposition of the antibiotics did not affect significantly analytical results. Comparative investigations have been carried out with 1--3 using t.l.c. and turbidimetry.

Rapid and sensitive direct TLC fluorometric method for evaluation of impurities in oxytetracycline

A rapid partition TLC method for the determination of oxytetracycline and its degradation products is described. Quantitative determinination of the substances is performed by direct TLC fluorometry in 2 hr using plates prepared previously.

Oxytetracycline residues in meat and kidney tissue after intramuscular or intramammary treatment as determined by a chemical-physical method and compared to a microbiological method

Two adult cows and three calves were treated intramuscularly with an oxytetracycline (OTC) preparation. The dose was about 5 mg/kg. The animals were slaughtered eight days after the treatment and their kidneys and muscle samples were taken for analysis. Twelve cows were treated intramammarily with an OTC preparation 12 hours before slaughter. Six of the cows were treated in two udder quarters with a preparation containing 200 mg OTC chloride per dose; the other six were similarly treated in four quarters with four doses. When the kidneys of all the animals were studied for the presence of inhibitory substances using the official Finnish microbiological meat inspection method, all were found negative. The OTC concentration of the different tissue samples was determined by a chemical-physical method, based on thin-layer chromatography and on the UV-fluorescence of OTC. The muscle samples of the cows given OTC i.m. were negative except near the site of injection, where the concentrations were 4 mg and less than 0.5 mg (traces) per kg. The corresponding kidney concentrations of OTC were less than 0.5 and about 0.5 mg per kg respectively. All except one kidney sample of the calves given OTC i.m. were found to be negative. Traces of OTC (less than 0.5 mg/kg) were found in all but one kidney sample of the cows treated intramammarily with OTC. Traces of OTC were found in two muscle samples of the cows treated intramammarily with 2 X 200 mg OTC and in two muscle samples of the cows similarly treated with 4 X 200 mg OTC. All the other samples were negative. The authors stress the need for a change in the present Finnish directives on the use of antibiotics in food animals.

Detection of antibiotic residues in calf tissues

Groups of calves were injected with penicillin, ampicillin or oxytetracycline and a variety of samples were taken from the calves when slaughtered and tested for the presence of antibiotic residues by microbiological assay. Diaphragm and urine samples were found to be suitable for measuring detectable levels of antibiotics in calves given therapeutic injections.

[Distribution and binding of oxytetracycline in the body of immunized animals]

Distribution and binding of oxytetracycline in immunized animals at various periods of immunogenesis (5, 10, 15, 20, 30 and 90 days after vaccination) were studied on rabbits, using dry live brucellosis vaccine, strain 19 as the antigen. The results of the study showed that immunological reconstruction of the macroorganism, its protective forces had a definite effect on the character of distribution, absorption and levels of oxytetracycline, as well as the processes of the antibiotic binding in the organism. The changes were indirect dependence on the immunogenesis periods: at the beginning of immunogenesis there was some increase in the antibiotic levels, as well as increased binding of the drug in the organs where reconstruction, activation and hyperplasia of the lymphoreticular cells occurred. During the productive phase of the antigen formation the antibiotic levels were 1,5-2 times lower, however, the processes of the antibiotic binding were more pronounced in the organs, where immunocompetent cells and antibodies were synthesized. During extinction of immunogenesis reduction of the initial antibiotic levels was recorded. Therefore, the changes directly depended on the periods of immunogenesis.

Some formulation factors affecting the tensile strength, disintegration and dissolution of uncoated oxytetracycline tablets

A study has been made of the effects of gelatin binding agent and moisture content on the tensile strength, disintegration and dissolution times of oxytetracycline tablets. These properties all increase with the gelatin content, and maximum tensile strengths occur when the tablets contain between 2.5 and 4.5% w/w of moisture. The properties of the tablets depend on their packing fraction and in general, the disintegration and dissolution times are minimal when the packing fraction is between 0.77 and 0.82. A connection has been established between the disintegration times of the tablets and the time required for 50% of the drug content to dissolve.

[Hygienic study of a proteolytic preparation obtained from Actinomyces]

An enzymatic preparation rimoprotelin, obtained from Actinomyces rumosus was studied. The results of a microbiological control analysis showed the preparation to contain admixtures of oxytetracycline in an amoun of 950 Un/g. In a 9-months long test with albino rats the enzymatic preparation produced substantial interferences in the composition to the intestinal microflora and increased the incidence of bacterial cultures resistent to oxytetracycline. Morphological changes in the organs and tissues of the test animals, which were, apparently, conditioned by the presence of the antibiotic admixture in the preparation were revealed. This point to the need of a thorough purification of this enzymatic preparation from the oxytetracycline admixture and makes its use as a food additive in its original form imposssible.

Survey of antibiotic residues in Canadian slaughter animals

Kidneys and urine of cattle, swine, sheep and chickens were tested for bacterial growth inhibitors using Bacillus subtilis and Sarcina lutea as test organisms. Results were as follows: 211 beef kidneys four positive, 611 swine kidneys five positive, 27 sheep and 120 chicken kidneys all negative, 2108 beef urine 76 positive, 2409 swine urine 186 positive, 176 sheep urine 17 positive. Strongest reactions were obtained with B. subtilis on phosphate buffered pH 6.0 plates. Larger zones were produced by urine from injected animals than by tissue samples.

Agar well technique for antibiotics in animal feeds

The agar well technique compares favorably with the cylinder plate assay in accuracy, sensitivity, and precision. It is more flexible and more rugged, and growth of seed organism is not inhibited. The wells are precision cut with Grafar gel punch assembly with sets (6) of 10, 7, 5, 4, and 3 mm cutters. The wells are easily and rapidly filled with short, disposable Pasteur pipets fitted with rubber bulbs. The smaller wells are filled with capillary pipets. The diameter of the well (independent of volume) appears to be a function of concentration. For every decrease in the diameter size of the well, concentration can be increased, at least to the next higher level of the standard response line. Extracts of chlortetracycline containing as much as 3.2 mu-g/ml can be analyzed if the 3 mm wells are used and with no sacrifice in accuracy or precision. This works especially well for antibiotic premixes. The technique has been used successfully for penicillin, streptomycin, chlortetracycline, oxytetracycline, oleandomycin, and tylosin.