Antibiotiki. 1976 Apr;21(4):365-8.
[Antibiotic sensitivity of the Salmonella isolated from humans ill with salmonellosis in 1967-1974]

[Article in Russian]

Garanin BA.

Sensitivity to levomycetin, streptomycin, chlortetracycline, oxtetracycline, tetracycline, neomycin, monomycin and erythromycin of 548 fresh isolates of Salmonella of 32 serotypes of the main groups A, B, C, D and E was studied. The cultures were isolated from salmonellosis patients within 1967-1974. Sensitivity to neomycin, monomycin, levomycetin and streptomycin was found respectively in 96.9, 91.1, 76.5 and 74.8 per cent of the cultures. High sensitivity of the cultures was observed only to levomycetin (15.1 per cent). With respect to tetracyclines the isolates were mainly resistant (24.2-47.2 per cent) or low sensitive (25-26.5 per cent). 70.3 per cent of the strains were resistant to erythromycin and 24.1 per cent were of low sensitivity. The causative agents of typhoid fever, paratyphoid fever A and B were more sensitive to levomycetin and tetracycline as compared to other Salmonella. A polyvalent Salmonella bacteriophage lyzed from 94.2 to 100 per cent of the Salmonella cultures tested.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=776082&dopt=Abstract antibiotics, tetracycline




J Bacteriol. 1995 Aug;177(15):4557-61.
Tetracycline/H+ antiport and Na+/H+ antiport catalyzed by the Bacillus subtilis TetA(L) transporter expressed in Escherichia coli.

Guffanti AA, Krulwich TA.

Department of Biochemistry, Mount Sinai School of Medicine of CUNY, New York 10029, USA.

The properties of TetA(L)-dependent tetracycline/proton and Na+/proton antiport were studied in energized everted vesicles of Escherichia coli transformed with a cloned tetA(L) gene (pJTA1) from Bacillus subtilis. Inhibition patterns by valinomycin and nigericin indicated that both antiports were electrogenic, in contrast to the tetracycline/proton antiport encoded by gram-negative plasmid tet genes. Tetracycline uptake in the everted system was dependent upon a divalent cation, with cobalt being the preferred one. The apparent Km for tetracycline was markedly increased at pH 8.5 versus pH 7.5, whereas the Vmax was unchanged. The much higher apparent Km for Na+ decreased at pH 8.5 relative to that at pH 7.5, as did the Vmax. Na+ did not affect tetracycline uptake, nor did Co2+ and/or tetracycline affect Na+ uptake; complex patterns of inhibition by amiloride and analogs thereof were observed.

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J Med Chem. 1994 Apr 29;37(9):1355-61.
Molecular requirements for the inhibition of the tetracycline antiport protein and the effect of potent inhibitors on the growth of tetracycline-resistant bacteria.

Nelson ML, Park BH, Levy SB.

Center for Adaptation Genetics and Drug Resistance, Tufts University, School of Medicine, Boston, Massachusetts 02111.

Forty-seven compounds and tetracycline (Tc) structural analogues were tested for their ability to interfere with [3H]Tc uptake in everted inner membrane vesicles derived from Tc-resistant Escherichia coli D1-209, bearing the class B tetracycline resistance efflux protein (Tet protein). For effective inhibition of Tc uptake, the molecule had to have an intact ABCD tetracyclic carbon skeleton and a conjugated phenolic beta-diketone substructure at positions 10-12a with the subsequent development of keto-enol tautomerization. Molecular variations at carbon positions 2, 4, 5, 6, 7, 8, and 9 did not decrease, and some increased, the inhibitory activity as compared to that of Tc. Among these compounds, the highest inhibition of uptake occurred with certain position 6 and 13 derivatives of 5-hydroxytetracycline. In a group of 13-(propylthio) derivatives of 5-OH-Tc [13-propyl, 13-(3-chloropropyl), and 13-(2-carboxyethyl)] there was a correlation between uptake inhibitory activity and antibacterial activity. The 13-(3-chloropropyl) derivative, with the best efflux inhibitory activity, exhibited synergistic activity when tested in combination with doxycycline against Tc-resistant E. coli bearing the class A or B determinant, against Staphylococcus aureus bearing class K, and against Enterococcus faecalis bearing the class L determinant. The 13-propyl analogue also showed high transport blocking activity and showed synergistic antibacterial activity against E. coli bearing the class A determinant and additive activity against the other Tc-resistant bacteria. The synergistic antibacterial activity of these compounds was not shown by the 13-[(2-carboxyethyl)thio] homologue, whose efflux blocking activity was 70-fold less. These findings suggest that multiple sites on the Tc molecule are available for synthetic modification toward the development of an effective Tc blocking agent. Such compounds, used alone or in combination with a standard tetracycline, show improved antibacterial activity.

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J Pharm Sci. 1999 Jan;88(1):111-20.
Importance of tautomers in the chemical behavior of tetracyclinesdagger.

Duarte HA, Carvalho S, Paniago EB, Simas AM.

Departamento de Quimica-ICEx, Universidade Federal de Minas Gerais, 31.270-901 Belo Horizonte-MG-Brazil.

We advance the concept that tautomerism is crucial for the understanding of the chemical behavior of tetracycline. Indeed, considering four deprotonations, there are 64 different possible tautomers to be considered for tetracycline. Our results indicate that tetracycline is a very adaptive molecule, capable of easily modifying itself through tautomerism in response to various chemical environments. Indeed, its situation in solution can be more accurately pictured as an equilibrium among a diversity of tautomeric species-an equilibrium that can be easily displaced depending on the various possible chemical perturbations, such as varying the pH or the dielectric constant of the solvent. Moreover, we also show that tetracycline could undergo four deprotonations and predict for it a fourth pKa of 13 and refer to our experimental determination of this parameter, which yielded the value of 12. We conclude that tautomerism is essential to the comprehension of the chemical behavior of tetracycline as determined by the semiempirical method AM1 as well as by the self-consistent reaction field method, which estimates the effects of the solvent on the tautomers. All tautomers in their different conformations have been fully optimized for each of the possible degrees of protonation of this molecule. Thus, the relative stabilities of the different tautomeric species have been computed.

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roche.com

Plasmids for the tetracycline regulated gene expression in Streptococcus pneumoniae have been developed. The plasmids were used for the tetracycline-dependent production of firefly luciferase in streptococci. The production of luciferase can be induced fivefold by the addition of tetracycline. By using two promoters of different strength and depending on the presence or absence of tetracycline, an 80-fold range of luciferase activities can be covered. The system was also used to construct strains that depend on the addition of tetracycline for the production of the A subunit of DNA gyrase, an essential streptococcal protein. The growth of such a strain depends on the addition of tetracycline to the medium. In the absence of tetracycline, the cells cease to grow and are not viable. The system presented in this report should be useful for the characterization of gene networks in S. pneumoniae. It especially allows one to study the function of essential genes that can not be investigated by standard knock-out techniques.

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Biull Eksp Biol Med. 1981 May;91(5):533-5.
[Reversible inhibition of thrombocyte physiology by tetracycline derivatives]

[Article in Russian]

Lisovskaia IL.

Tetracycline and its derivatives (hydroxytetracycline and chlortetracycline) exert an inhibitory action, within a concentration range of 50-1000 microM on the basic functions of human platelets: aggregation, adhesion, retraction, hypotonic shock response, and release reaction. After resuspending and transfer of the inhibited platelets into plasma not containing tetracycline derivatives the functional activity of platelets partially or completely recovered. The evidence obtained suggests that the reversible inhibitory action of tetracycline results from its ability to easily penetrate the cell membranes and to bind intracellular calcium without substantial damage to the cells.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7260378&dopt=Abstract antibiotics, tetracycline




Plasmid. 1984 Sep;12(2):103-10.
Plasmid vectors based on Tn10 DNA: gene expression regulated by tetracycline.

de la Torre JC, Ortin J, Domingo E, Delamarter J, Allet B, Davies J, Bertrand KP, Wray LV Jr, Reznikoff WS.

The regulatory region of the tetracycline resistance determinant from transposon Tn10 has been used to construct plasmid vectors for gene expression regulated by tetracycline. Plasmids pRS tetBam-8 and pRS tetBam-16 include the tet regulatory region, the segment coding for the first four amino acids of the tetracycline resistance protein (tetA protein), and a linker region with SalI, HpaII, and BamHI restriction sites for gene fusions. Plasmid pTB-1, a derivative of pRS tetBam-8 and of the beta-galactosidase gene-containing plasmid pMC1403, constitutively expresses a tetA fragment-beta-galactosidase fusion protein. If a multicopy runaway replication plasmid, pMOBglII-16 that includes a 2.7-kb BglII DNA fragment from Tnl10 that provides tetR protein is present along with pTB-1, the expression of beta-galactosidase is reduced eightfold. Tetracycline acts as an inducer of the system and restores the level of beta-galactosidase activity measured in transformants containing pTB-1 alone. Plasmid mutants unable to produce active tetR protein are ineffective in reducing expression. Escherichia coli carrying plasmids that express both tetA protein and tetR protein show an increase in the tetracycline resistance level after incubation with the drug. The observations are consistent with the previously proposed mechanism of regulation of tetracycline resistance in Tn10.

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Mol Microbiol. 1996 Jan;19(1):187-95.
Purification of the Tn10-specified tetracycline efflux antiporter TetA in a native state as a polyhistidine fusion protein.

Aldema ML, McMurry LM, Walmsley AR, Levy SB.

Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA.

The bacterial tetracycline-resistance determinant from Tn10 encodes a 43 kDa membrane protein, TetA, responsible for active efflux of tetracyclines. The tetA gene was cloned behind a T7 promoter/lac operator in a plasmid that provided fusion of TetA to a polyhistidine-carboxy terminal tail. A second plasmid provided a regulated T7 RNA polymerase. The specific activity of the TetA fusion protein was between 10-40% that of the wild-type protein as assayed by tetracycline resistance in cells and by transport in membrane vesicles. The fusion protein, overproduced approximately 3-13-fold, was purified by nickel chelation chromatography. Calculations from circular dichroism spectra of the purified protein solubilized in dodecylmaltoside gave an alpha-helix content of 54-64%, close to the 68% predicted from the amino acid sequence by hydropathy analysis (12 membrane-spanning helices) for the native protein in the membrane bilayer. Fluorescence studies showed binding activity of the purified protein to its substrate, the tetracycline analogue 13-(cyclopentylthio)-5-hydroxy-6-alpha-deoxytetracycline. These findings suggested that the purified protein was in a native state.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8821947&dopt=Abstract antibiotics, tetracycline