Curr Microbiol. 1996 May;32(5):286-90.
A phage-mediated transfer of chromosomally integrated tetracycline resistance plasmid in Staphylococcus aureus.

Udo EE, Grubb WB.

Department of Microbiology, Faculty of Medicine, Kuwait University, Safat.

The ability of a Staphylococcus aureus isolate WBG7416 to transfer its resistance determinants was studied in conjugation and mixed-culture transfer experiments. It carried plasmid-borne resistance to kanamycin, trimethoprim, chloramphenicol, cadmium, propamidine isethionate, and chromosomal resistance to methicillin, gentamicin, streptomycin, erythromycin, clindamycin, tetracycline, and minocycline. It transferred tetracycline resistance in mixed-culture transfer but not in conjugation experiments. DNA-DNA hybridization of genomic DNA from the tetracycline-resistant transferrants against a labeled tetracycline resistance plasmid, pWBG3, probe revealed the presence of an integrated plasmid in their chromosomes. In contrast, no homology to the probe was detected in the chromosome of a tetracycline-resistant mutant of the recipient strain. The results established a role for a bacteriophage in the transfer of chromosomal tetracycline resistance in WBG7416 besides demonstrating the presence of an integrated tetracycline resistance plasmid in the transferrants. It also offered an insight into the nature of the integrated plasmid.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8857274&dopt=Abstract antibiotics, tetracycline




Biotechniques. 1996 Oct;21(4):718-22, 724-5.
Establishment of stable cell lines expressing potentially toxic proteins by tetracycline-regulated and epitope-tagging methods.

Wu SY, Chiang CM.

Department of Biochemistry, University of Illinois at Urbana-Champaign 61801, USA.

A tetracycline-regulated expression system is combined with the FLAG-epitope tagging method for conditional expression of potentially toxic proteins in mammalian cells. This strategy allows a controlled expression of exogenous gene products and also provides a unique way of protein purification. Two mammalian expression plasmids containing the FLAG sequence and flanking multiple cloning sites were created for conditional protein expression. The cDNAs encoding human basal transcription factors TBP, TAFII55 and the p62 subunit of TFIIH were individually cloned into these vectors and introduced into a HeLa-derived cell line that constitutively expresses a tetracycline-regulated transactivator (tTA). The established clonal human cell lines express FLAG-tagged basal transcription factors in a manner modulated by the amount of tetracycline in the growth medium. In the absence of tetracycline, tTA binds to the DNA recognition sites of the expression plasmid and induces the expression of tagged proteins. When tetracycline is added back to the growth medium, the induced protein starts to decay. This provides us with an estimation of the in vivo half-lives of TBP and TAFII55, which were assessed to be less than 20 and 6 hours, respectively, in HeLa cells. The level of induced proteins in the absence of tetracycline could be further enhanced by including the antibiotic G418 to presumably boost the production of tTA which in turn activates the expression of tagged proteins.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8891226&dopt=Abstract antibiotics, tetracycline




Hum Gene Ther. 1997 Jan 20;8(2):195-204.
Modulation of erythropoietin delivery from engineered muscles in mice.

Bohl D, Heard JM.

Laboratoire Retrovirus et Transfert Genetique, Institut Pasteur, Paris, France.

In most relevant diseases, the permanent systemic delivery of a therapeutic protein from engineered cells might be proposed only if secretion levels can be regulated. The tetracycline resistance operon of Escherichia coli provides a transcriptional regulatory system effective in mammalian cells, which could be used for that purpose. A chimeric transactivator (tTA) consisting of the tetracycline repressor fused to the transactivation domain of the herpes simplex virus VP16 protein stimulates transcription by binding a minimal cytomegalovirus (CMV) promoter containing repeats of the tetracycline operator (tetO-CMV). Binding is abolished by tetracycline, thus impairing promoter activation. We have transduced C2.7 myoblasts with two U3-deleted retroviral vectors containing these regulatory elements. The tetP-Epo vector expressed the murine erythropoietin (Epo) cDNA under the control of the tetO-CMV promoter. The D-De-tTA vector expressed tTA under the control of the muscle-specific human desmin enhancer-promoter. Northern blot analysis showed background Epo mRNA expression in myoblasts. Myotubes differentiation induced tTA expression, leading to a 28-fold increase of Epo mRNAs, which was suppressed by tetracycline. Basal Epo secretion in myoblasts increased 23- to 41-fold during the formation of multinucleated myotubes, and turned back close to myoblast level when tetracycline was added. Myoblasts transduced with both vectors and treated with mitomycin with the aim to prevent tumor formation were engrafted in skeletal muscles of syngeneic C3H mice. Hematocrit levels were significantly higher in animals bearing cells transduced with both vectors than in control animals grafted with cells transduced with the Epo vector only. This difference was abolished when tetracycline was given to mice. These data indicate that the tetracycline regulatory elements can modulate transcription in the context of retroviral vector genomes, and that this system can be used to control the in vivo delivery of a therapeutic protein from genetically modified muscles.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9017423&dopt=Abstract antibiotics, tetracycline




Vet Med (Praha). 1996 Nov;41(11):329-33.
[Oxytetracycline in the milk of dairy cows with clinical signs of mastitis during the lactation period]

[Article in Slovak]

Dudrikova E, Sokol J, Burdova O, Turek P, Cabadaj R.

University of Veterinary Medicine, Kosice, Slovak Republic.

The objective of this study was to determine the oxytetracycline residues in milk from cows with clinical mastitis dosed with two extra-label routes of oxytetracycline administration not only during antibiotic's treatment (5 days), but also six days after treatment by use of a liquid chromatography method of testing with a detection limit of 20 ppb. Both groups of animals were treated once daily for five milkings at 24-hour intervals following morning milkings. Composite milk samples (equal volumes of foremilk from each quarter) were collected during morning and afternoon milkings, mixed together (1:1), and stored until analyzed. Milk samples were analyzed just before the first treatment (0 hour) and ten times at 24-hour intervals. Residue studies in milk cows indicate that oxytetracycline passes into milk. Residues in milk were higher for the cows receiving oxytetracycline by intramammary route (Tab. I) than for the cows receiving oxytetracycline intramuscularly (Tab. II). The highest mean data were 195.68 mg/kg after intramammary infusion (Fig. 2) and 2.74 mg/kg after intramuscular injection (Fig. 3) on the 5th day of the treatment beginning. The analysis data showed that oxytetracycline persisted in milk for as long as two days after both treatments at the concentration 0.03 mg/kg versus 0.02 mg/kg, respectively. No residues were detected in milk of any animal from the 4th day of the cessation of the therapy (Fig. 1) as detected by the HPLC method.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9036618&dopt=Abstract antibiotics, tetracycline




Biochimie. 1996;78(10):868-73.
Tetracyclines induce changes in accessibility of ribosomal proteins to proteases.

Kolesnikov IV, Protasova NY, Gudkov AT.

Institute of Protein Research, Russian Academy of Sciences, Moscow Region, Russia.

Limited proteolysis was used to test the interaction of tetracyclines and some of their derivatives with ribosomes. Proteolysis of the free ribosomes was compared with that of the ligand-bound ribosomes. The interaction of different tetracyclines with ribosomes depends on their chemical structure and produces both a protective effect and an increased susceptibility to proteases of some ribosomal proteins in the 30S and 50S subparticles. Most of the proteins affected by tetracycline action are located on the head of the 30S and interface side of the 50S subunits. On the grounds of the obtained data one of the antibiotic-binding regions can be located near the ribosomal peptidyl transferase center. The effect of possible conformational changes induced by tetracyclines on the translation process is discussed.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9116057&dopt=Abstract antibiotics, tetracycline




J Vet Pharmacol Ther. 1997 Aug;20(4):262-6.
Comparative pharmacokinetics of ampicillin trihydrate, gentamicin sulphate and oxytetracycline hydrochloride in Nubian goats and desert sheep.

Elsheikh HA, Osman IA, Ali BH.

Department of Veterinary Medicine, Pharmacology and Toxicology, University of Khartoum, Khartoum North, Sudan.

In this investigation the pharmacokinetics of three commonly used antibiotics, ampicillin trihydrate (10 mg/kg), gentamicin sulphate (3 mg/kg) and oxytetracycline hydrochloride (5 mg/kg), given intravenously, were each studied in five Nubian goats and five desert sheep. The pharmacokinetic parameters were described by a two-compartment open model. The results indicated that there were significant differences between the two species in some kinetic parameters of ampicillin and oxytetracycline but not gentamicin. Ampicillin elimination half life (t[1/2beta]) in goats (1.20 h) was shorter than that in sheep (2.48 h), and its clearance (Cl) significantly higher in goats (2921 mL/h x kg) compared to sheep (262 mL/h x kg) (P < 0.01). Ampicillin volume of distribution (Vd[area]) was found to be significantly larger in goats (5673 mL/kg) than in sheep (992 mL/kg) (P < 0.01). For oxytetracycline, the t(1/2beta) in goats (3.89 h) was significantly shorter than that in sheep (6.30 h) and the Cl value in goats (437 mL/h x kg) was significantly higher than in sheep (281 mL/h x kg). The results suggest that when treating sheep and goats, the pharmacokinetic differences between the two species must be considered in order to optimize the therapeutic doses of ampicillin and oxytetracycline.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9280365&dopt=Abstract antibiotics, tetracycline




Enzyme Microb Technol. 1997 Oct;21(5):314-20.
Response surface analysis of chlortetracycline and tetracycline production with K-carrageenan immobilized Streptomyces aureofaciens.

Asanza Teruel ML, Gontier E, Bienaime C, Nava Saucedo JE, Barbotin JN.

Laboratoire de Genie Cellulaire, UPRES A CNRS 6022, Faculte des Sciences, Universite de Picardie Jules Verne, Amiens, France.

A full-factorial experimental design at three levels with two independent variables, carrageenan concentration (1.0, 1.5, and 2.0%) and potassium chloride concentration (0.3, 0.7, and 1.1 M) was studied in order to analyze the effect of both factors on the antibiotic production of K-carrageenan-immobilized mycelia of Streptomyces aureofaciens. The response surfaces obtained have indicated that both carrageenan and potassium chloride concentrations have a pronounced effect on the yield of chlortetracycline (CTC) and tetracycline (TC) produced by S. aureofaciens. By exclusively varying the immobilization conditions, the tetracycline production can be enhanced more than eight times (12.3 mg g-1 biomass for immobilized cells vs. 1.5 mg g-1 biomass for free cells) in comparison with free-cell mycelial cultures.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9322372&dopt=Abstract antibiotics, tetracycline




J Chromatogr A. 1997 Aug 29;779(1-2):235-43.
Use of metal complexation in non-aqueous capillary electrophoresis systems for the separation and improved detection of tetracyclines.

Tjornelund J, Hansen SH.

Royal Danish School of Pharmacy, Department of Analytical and Pharmaceutical Chemistry, Copenhagen, Denmark.

Metal complexation in non-aqueous capillary electrophoresis systems was evaluated for the separation and improved detection of tetracycline antibiotics using laser-induced fluorescence detection. It was found that three factors were important for the choice of complexing agent: (i) it should be soluble in the organic solvent used for the separation, (ii) it should have a sufficient fast complexing rate so as not to invalidate the electrophoretic separation and, (iii) it should give a large increase in the fluorescence intensity. Mg2+ ions were found to be the most suitable ions for the separation of the tetracyclines as the acetate salt of magnesium is very soluble in organic solvents and only a relatively low current was generated during electrophoresis making it possible to use high concentrations of the complexing metal ion. Metal complexation strongly intensified the fluorescence of tetracyclines and all organic solvents investigated further intensified the fluorescence, e.g. dimethylformamide improved the fluorescence of the oxytetracycline metal complex by a factor of 34 compared to water. However, magnesium acetate was not sufficiently soluble in dimethylformamide and therefore N-methylformamide, improving the fluorescence intensity by only a factor of 9, was used. It was demonstrated that the method can be used for the detection of tetracyclines at the ppb level in milk and plasma.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9335125&dopt=Abstract antibiotics, tetracycline