J Bacteriol. 1999 Jan;181(2):618-26.
Cloning and characterization of a tetracycline resistance determinant present in Agrobacterium tumefaciens C58.

Luo ZQ, Farrand SK.

Departments of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.

Agrobacterium tumefaciens C58 and its derivatives give rise to spontaneous mutants resistant to tetracycline at a high frequency. We observed that a mutation affecting a tRNA processing function significantly affected the emergence of such mutants, suggesting that C58 contained a positively acting gene conferring resistance to tetracycline. A cosmid clone conferring resistance to tetracycline in Escherichia coli and Agrobacterium was isolated from a genomic bank of one such mutant. Subcloning, transposon mutagenesis, and DNA sequence analysis revealed that this DNA fragment contained two divergently transcribed genes, tetA and tetR, encoding products that were very similar to proteins of the Tet(A) class of tetracycline resistance systems. In the clone from this mutant, tetR was disrupted by an IS426. The homologous region from wild-type NT1 contained an intact tetR gene and did not confer resistance to tetracycline. Hybridization analysis showed that of 22 members of the genus Agrobacterium surveyed, only strains C58 and T37 contained the tet determinant. Moreover, only these two strains mutated to resistance to this antibiotic. Unlike other Tet(A) systems, neither tetracycline nor a series of its derivatives induced the expression of this tet gene unit. Other polycyclic compounds, including many of plant origin, also did not induce this tet gene system. The divergent promoter region of this tet system contained a single inverted repeat element identical to one such operator repeat in the promoter region of the tet determinant from the IncP1alpha R plasmid RP4. TetR repressor proteins from the Agrobacterium tet system and from RP4 interacted with the heterologous operators. While the repressive effect of the TetR protein from strain C58 (TetRC58) on the tetA gene from strain RP4 (tetARP4) was not relieved by tetracycline, repression of tetAC58 by TetRRP4 was lifted by this antibiotic.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9882678&dopt=Abstract antibiotics, tetracycline




J Pharm Sci. 1979 Aug;68(8):1061-3.
Differential pulse polarography of tetracycline: determination of complexing tendencies of tetracycline analogs in the presence of cations.

Jochsberger T, Cutie A, Mills J.

The complexation tendencies, stoichiometries, and stability constants for tetracycline, minocycline, and demeclocycline with the metallic ions calcium(II), magnesium (II), zinc(II), aluminum(III), iron(II), and iron (III) were evaluated using a polarographic technique. Changes in pulse peak heights for each tetracycline deravative were measured as a function of cation concentration. The method provides an in vitro method of evaluating the selectivity of particular metal ions for different tetracycline analogs.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=480164&dopt=Abstract antibiotics, tetracycline




J Clin Invest. 1983 Oct;72(4):1326-35.
Role of complement and polymorphonuclear cells in demethylchlortetracycline-induced phototoxicity in guinea pigs. Inhibition by decomplementation in vivo.

Lim HW, Novotny H, Gigli I.

In this study, demethylchlortetracycline was used as a prototype of exogenous phototoxic substances. In vitro, exposure of serum containing demethylchlortetracycline to ultraviolet-A irradiation resulted in the diminution of total complement hemolytic activity and C4, C2, C3, and C5 activities. In addition, chemotactic activity for human polymorphonuclear cells was generated, which was thermostable and antigenically related to human C5 but not human C3. In vivo, phototoxic lesions were induced in guinea pigs upon intradermal injections of demethylchlortetracycline solution, followed by ultraviolet-A irradiation. On a scale of 0-3+, the animals developed a maximal response of 2.5 at 20 h. This clinical response was associated with cellular infiltrate in the dermis, consisting of 29 +/- 2% of neutrophils at 24 h. The participation of the polymorphonuclear cells was evaluated in guinea pigs rendered neutropenic by treatment with cyclophosphamide. In these guinea pigs, demethylchlortetracycline and ultraviolet-A induced a maximal response of 0.75 +/- 0.5, which was associated histologically with 1.2 +/- 0.5% neutrophils in the dermis. The role of complement in this process was studied in guinea pigs congenitally deficient in C4, and in guinea pigs decomplemented by treatment with cobra venom factor. In contrast to normal guinea pigs, C4-deficient animals exhibited a maximal reaction of 0.83 +/- 0.16 at 6 h, which subsided within 24 h. Cobra venom factor-treated guinea pigs developed a maximal response of 0.5 at 0.5 and at 6 h. These clinical changes were associated with the development of an increased vascular permeability, as demonstrated by studies using guinea pigs injected intravenously with Evans blue solution. In animals with a normal complement system, there was intense localized bluing at the sites of phototoxic lesion. In contrast, only minimal bluing was observed in decomplemented guinea pigs. These data indicate that a normal number of polymorphonuclear cells and an intact complement system are required for the full development of demethylchlortetracycline-induced phototoxic lesions.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=6415108&dopt=Abstract antibiotics, tetracycline




AAPS PharmSci. 2002;4(4):20.
Bioerodible injectable poly(ortho ester) for tetracycline controlled delivery to periodontal pockets: preliminary trial in humans.

Schwach-Abdellaoui K, Loup PJ, Vivien-Castioni N, Mombelli A, Baehni P, Barr J, Heller J, Gurny R.

School of Pharmacy, University of Geneva, Switzerland.

The semisolid consistency of poly(ortho esters) (POEs) containing tetracycline free base allows direct injection in the periodontal pocket and shows sustained and almost constant in vitro release in phosphate buffer, pH 7.4 at 37 degrees C, for up to 14 days. Total polymer degradation concomitant with drug release was obtained. Formulations containing 10% or 20% (wt/wt) tetracycline were evaluated in a panel of 12 patients suffering from severe and recurrent periodontitis. In the first trial including 6 patients, single-rooted teeth and molar teeth with furcations were treated immediately after scaling and root planing. Patients tolerated both formulations well, experienced no pain during application, and showed no signs of irritation or discomfort during the observation period. However, retention of the formulation was minimal in this first study. An improved clinical protocol followed in the second study (stopping bleeding after scaling and root planning) prolonged the retention of the formulations in the inflamed periodontal pockets. For up to 11 days, tetracycline concentrations in the gingival crevicular fluid were higher than the minimum inhibitory concentration of tetracycline against most periodontal pathogens.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12645992&dopt=Abstract antibiotics, tetracycline




J Periodontol. 1999 Sep;70(9):1008-16.
Tetracycline-coated polytetrafluoroethylene barrier membranes in the treatment of intraosseous periodontal lesions.

Zarkesh N, Nowzari H, Morrison JL, Slots J.

School of Dentistry, Department of Periodontology, University of Southern California, Los Angeles 90089-0641, USA.

BACKGROUND: Periodontal pathogens are detrimental to periodontal healing in barrier membrane-assisted periodontal therapy. Tetracycline-coating of barrier membranes may reduce levels of infecting pathogens. This study evaluated the clinical and microbiological effects of tetracycline-coated expanded polytetrafluoroethylene (T-ePTFE) barrier membranes in the treatment of 2- to 3-wall intraosseous periodontal lesions around mandibular molars. METHODS: Eleven patients received non-coated barrier membranes (ePTFE) and 11 patients received T-ePTFE barrier membranes. Tetracycline coating was performed by placing ePTFE membranes first in a 5% tridodecylmethylammonium chloride solution and then in a basic 3% tetracycline solution. Microbiological examination included conventional culture and DNA probe analyses. Barrier membranes were removed 6 weeks after insertion. RESULTS: At baseline, the periodontal lesion depth averaged 8.0 mm in the ePTFE treated group and 7.4 mm in the T-ePTFE group. At 1 year post-treatment, the mean gain of probing attachment was 1.9 mm in the ePTFE group and 3.3 mm in the T-ePTFE group (P = 0.02). At 3 minutes after membrane placement, suspected periodontal pathogens were detected in several ePTFE membranes but only in one T-ePTFE membrane. At 6 weeks, all membranes showed periodontal pathogens, including Porphyromonas gingivalis, Fusobacterium species, Peptostreptococcus micros, Bacteroides forsythus, and motile rods. CONCLUSIONS: This study suggests that the use of tetracycline-coated ePTFE barrier membranes can result in additional gain of clinical periodontal attachment, most likely due to the antimicrobial properties of tetracycline during initial healing.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10505803&dopt=Abstract antibiotics, tetracycline




Antimicrob Agents Chemother. 1992 Apr;36(4):876-8.
Tet determinants provide poor protection against some tetracyclines: further evidence for division of tetracyclines into two classes.

Oliva B, Chopra I.

Department of Microbial Biochemistry and Genetics, American Cyanamid, Lederle Laboratories, Pearl River, New York 10965.

Atypical tetracyclines were active against Escherichia coli and Staphylococcus aureus strains containing determinants that mediate resistance to typical tetracyclines by efflux (Tet B and Tet K) or ribosomal protection (Tet M) mechanisms. The results support recently published data that tetracyclines are divisible into at least two classes on the basis of their modes of action.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1503452&dopt=Abstract antibiotics, tetracycline




Gene. 2002 Jan 9;282(1-2):65-74.
Effects of mouse strain, position of integration and tetracycline analogue on the tetracycline conditional system in transgenic mice.

Robertson A, Perea J, Tolmachova T, Thomas PK, Huxley C.

Imperial College School of Science, Technology and Medicine, Division of Biomedical Sciences and Clinical Sciences Centre, London, UK.

The tetracycline conditional system is a very powerful method for achieving control of gene expression in transgenic mice, allowing one to turn expression both off and on in the same animal. We have used it to make a tissue-specific transgenic mouse model of Charcot-Marie-Tooth disease type 1A. This disease is most commonly caused by overexpression of peripheral myelin protein 22 (PMP22) in Schwann cells of the peripheral nervous system. Here we describe the effects of position of integration of the transgene, tetracycline analogue and mouse strain in this model. The small transgenes used to express tTA, the LacZ reporter and the pmp22 cDNA were all very dependent on the position of integration with few of the transgenic lines working successfully. In contrast, the single transgenic made with the 560 kb yeast artificial chromosome construct containing the tTA open reading frame worked well. Tetracycline was found to be cleared from mice relatively fast in comparison with doxycycline and is thus useful if one wants to switch on gene expression after extended periods of administration. Finally, the initial litters were on a mixed genetic background and the level of LacZ or pmp22 expression was very variable between mice. We found that expression became uniform between mice, and occurred in a higher proportion of cells, when the transgenes were crossed onto the CBA/Ca background in comparison with the C57BL/6J background.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11814678&dopt=Abstract antibiotics, tetracycline

kyowa.co.jp

The secondary metabolite 6-demethylchlortetracycline (6-DCT), which is produced by Streptomyces aureofaciens, is used as a precursor of semisynthetic tetracyclines. Strains that produce 6-DCT also produce a melanin-like pigment (MP). The correlation between MP production and 6-DCT production was investigated by using S. aureofaciens NRRL 3203. Production of both MP and 6-DCT was repressed by phosphate or ammonium ions, suggesting that syntheses of these compounds are controlled by the same regulators. Ten chlortetracycline-producing recombinants were derived from 6-DCT-producing mutant NRRL 3203 by gene replacement. All of the recombinants produced chlortetracycline but not MP, indicating that MP production is the results of a defect in the 6-methylation step and suggesting that the polyketide nonaketideamide is a common intermediate leading to MP as well as 6-DCT. To further examine the possibility that MP might be synthesized via the 6-DCT-biosynthetic pathway, mutants defective in 6-DCT biosynthesis were derived from a 6-DCT producer. Some of these mutants were able to produce MP, while others, including mutants with mutations in the gene encoding anhydrotetracycline oxygenase, an enzyme catalyzing the penultimate step in the pathway, produced neither 6-DCT nor MP. Production of 6-DCT and production of MP were restored simultaneously by integrative transformation with the corresponding 6-DCT-biosynthetic genes, indicating that some of 6-DCT-biosynthetic enzymes are indispensable for MP production. These findings suggest that a defect in the 6-methylation step results in redirection of carbon flux from a certain intermediate in the 6-DCT-biosynthetic pathway to a shunt pathway and results in MP production.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10742218&dopt=Abstract antibiotics, tetracycline