Successful Tigecycline Use in Combined Therapy of Ventilator-Associated Hospital-Acquired Pneumonia: a Clinical Case.

In patients under artificial lung ventilation (ALV) there is often observed development of severe ventilator-associated pneumonia (VAP) due to polyresistant hospital pathogens. It should be noted that in the patient described here with the initial diagnosis of community-acquired pneumonia rapidly subjected to prolonged ALV the previous antibacterial therapy by broad spectrum drugs significantly increased the risk of contamination just by multiresistant nosocomial strains, which hampered the starting therapy of nosocomial pneumonia either when there were not available or sometimes there were available microbial cultures. When the treatment of severe pneumonias caused by multiresistant hospital flora resistant to carbapenems is actual, in the alternative therapy it could be used tigecycline, a tetracycline from the group of glycylcyclines. A case of successful treatment of nosocomial VAP by tigecycline based on the results of the bronchoalveolar lavage (BAL) culture is described. The case is of interest because tigecycline was used as off label.

[Interaction between RNA molecules of a two-componet trans-analog of antigenomic HDV-ribozyme].

Association of RNA molecules forming a two-component B:LS trans-analog of antigenomic HDV ribozyme was studied. From previously synthesized trans-ribozymes the B:LS ribozyme differs by length and sequence of its RNA molecules (33 and 34 bp, respectively), topology of functional parts and the absence of very short reaction product. The ribozyme displays a biphasic kinetics of self-cleavage similar to that of cis-ribozyme. Our original kinetic scheme for the B:LS trans-ribozyme self-cleavage (www.cardio.ru\labgen\RZ_e.html)describes a possible cause of biphasic nature of the reaction curve, namely, variation of the rate-limiting stage in the series of successive conformational transformations which coincide with the ribozyme self-cleavage. Interactions between the molecules involved in the reaction, i.e., "multimerization" of entire ribozyme and its components can be regarded as another cause of the biphasic kinetics. B:LS trans-ribozyme is a convenient model for the investigation of this process, since the binding of LS and B allows the formation of complexes with 1B:2LS or 2B:1LS stoichiometry and complexes with the cleavage products. We examined the factors determining dissociation-association of the ribozyme components using a series of electrophoreses under nondenaturing conditions. The possibility of interaction between cis- and transribozyme components was confirmed experimentally. In the presence of LS excess over B the ribozyme can form multimeres. These findings suggest the involvement of intermolecular interactions in native cis-ribozyme self-cleavage.

[Properties of antigenomic HDV ribozyme consisting of two RNA chains]. / Svoistva antigenomnogo HDV-ribozima, sostoiashchego iz dvukh molekul RNK.

B : LS ribozyme, a trans-variant of naturally occurring HDV ribozyme, has been constructed. The ribozyme consists of a substrate-containing LS chain and an enzyme B chain and differs from previously constructed trans-ribozymes in the length and nucleotide sequence of its oligonucleotide chains (34 and 33 bp, respectively). The chains readily associate with each other at a room temperature while the LS cleavage reaction at this temperature is negligible slow, which allowed us to investigate the association of the intact chains. At the same time the self-cleavage rate constant for the trans-ribozyme B : LS at 50 degrees C is close to those for the previously studied permuted cis-ribozymes, especially LSB variant. In addition, the dependence on the reaction conditions (Mg2+ concentration, pH, temperature) of the trans-ribozyme was similar to that of cis-ribozyme. Similar to other trans-ribozymes, B : LS ribozyme demonstrates the ability for multiple use of the enzyme B-chain with an excess of the substrate LS chain. The kinetics model of self-cleavage reaction for B : LS is presented in http://www.cardio.ru/labgen/RZ_r.html. Taken together, our results show that the original trans-variant of HDV ribozyme can be used as a model for the investigation of self-cleavage process of HDV ribozymes.

Properties of antigenomic hepatitis delta virus ribozyme that consists of three RNA oligomer strands.

A three-strand ribozyme, a derivative of antigenomic hepatitis delta virus (HDV) ribozyme, which consists of subfragments of 16 (L), 17 (S), and 33 nucleotides (B), has been constructed. The ternary B-L-S complex formed by the subfragments in stoichiometric ratio was able to catalyze a self-cleavage reaction. Kinetics of this reaction exhibited biphasic behavior and the same parameters as in the case of natural cis-ribozyme. Study of kinetics of reaction initiated by adding various reaction components and the study of binary complex formation between subfragments B and L, B and S, and also ternary B-L-S complex formation revealed that: 1) in the presence of Mg2+, B and S form a stoichiometric complex, L and S do not form complex at all, while B and L form 2 types of complexes, probably B-L and 2B-L; and addition of S subfragment prevented the formation of the latter complex; 2) the reaction initiated by S subfragment proceeds much slower than that initiated by other components pointing to the possibility that in the absence of S L may form a nonproductive complex with B, which is slowly displaced by S followed by productive ternary complex formation. Dissociation constants for binary B-L, B-S and ternary B-L-S complexes have been estimated.

[Derivatives of ddUTP, modified at the 5-position of uridine, as substrate terminators of reverse transcriptase. Hydrolysis of oligonucleotides, terminated by these analogs, by phosphodiesterase I]. / Proizvodnye ddUTP, modifitsirovannye v 5-polozhenii uridina, kak substratnye terminatory obratnykh transkriptaz. Gidroliz oligonukleotidov, terminirovannykh étimi analogami, fosfodiésterazoi I.

Synthesis of 2',3'-dideoxyuridine 5'-triphosphate analogues with fluorescent and biotin residues at C5 of uracil base was carried out. The substrate properties of these analogues were studied with AMV, M-MLV, and HIV reverse transcriptase. All 5-derivatives studied were shown to be incorporated into the 3'-terminus of oligonucleotide. The stability of oligodeoxyribonucleotides terminated with ddUTP analogues modified at the 5-position of the pyrimidine residue to the exonuclease action of phosphodiesterase I and Klenow enzyme was more than 1000 times higher than that of nonterminated oligonucleotides.

[Reverse transcriptase of the human immunodeficiency virus: isolation and substrate specificity]. / Obratnaia transkriptaza virusa immunodefitsita cheloveka: vydelenie i substratnaia spetsifichenost'.

Human immunodeficiency virus (HIV-I) reverse transcriptase was expressed in E. coli and purified to homogeneity (E. coli strain RRI (pRC-RT, pRK 248cIts)). We have investigated the substrate properties toward to DNA synthesis, catalyzed by this enzyme, of some nucleoside-5'-triphosphate analogues, previously studied in the same reactions, catalyzed by AMV and M-MLV reverse transcriptases. We have investigated substrate properties of new analogues of 2',3'-dideoxy-2',3'-didehydro- and 2',3'-dideoxytubercidin-5'-triphosphates. We have compared the relative efficiency of incorporation of different analogues tested in the DNA chain. It has been shown that expressed and purified HIV reverse transcriptase had the same specificity to analogues of 2'-deoxyribonucleoside-5'-triphosphates as was described for reverse transcriptases and natural HIV reverse transcriptase as well. These properties allow to apply the expressed HIV reverse transcriptase in different model systems.

[Analogs of nucleotides, modified by a sugar residue and pyrimidine base, in a DNA synthesis reaction, catalyzed by Thermus aquaticus DNA polymerase]. / Analogi nukleotidov, modifitsirovannye po sakharnomu ostatku i pyrimidinovomu osnovaniiu, v reaktsii sinteza DNK, kataliziruemogo DNK-polimerazoi Thermus aquaticus.

Substrate properties of dNTP analogues in the DNA synthesis reaction catalyzed by Thermus aquaticus DNA polymerase were studied. It was shown that most of dNTP analogues which were known as terminators of DNA synthesis of E. coli DNA polymerase I were able to terminate DNA synthesis catalyzed by Thermus aquaticus DNA polymerase. An interesting feature of Thermus aquaticus DNA polymerase was the ability to utilize 3'-azido-2',3'-dideoxythymidine triphosphate as terminating substrate. Relative efficiency of tested dNTP analogues incorporation into the DNA growing chain was estimated.

[Fluorescent analogs of nucleoside-5'-phosphates for the study of nucleic acids by nonradioactive methods]. / Fluorestsentnye analogi nukleozid-5'-trifosfatov dlia izucheniia nukleinovykh kislot neradioaktivnymi metodami.

The synthesis of 2'-deoxyuridine 5'-triphosphate analogues with fluorescent residues of fluorescein and rhodamine nature at C5 of the uracil base was performed. Reverse transcriptase of avian myeloblastosis virus, DNA polymerase beta of rat liver, terminal deoxynucleotidyl transferase of calf thymus and E. coli DNA polymerase I, Klenow fragment, were shown to be capable to incorporate a nucleotide residue with fluorescent label into 3'-terminus of oligonucleotide. These fluorescent labeled oligonucleotides were used as primers for synthesis of (-)-chain of M13mp10 phage. Fluorescently labeling template-primer complexes were used for DNA sequencing.