hygromycin-a and apramycin

Bacterial resistance to antibiotics is often plasmid-mediated and the associated genes encoded by transposable elements. These elements play a central role in evolution by providing mechanisms for the generation of diversity and, in conjunction with DNA transfer systems, for the dissemination of resistances to other bacteria. At the University Hospital of Zaragoza, extensive efforts have been made to define both the dissemination and evolution of antibiotic resistance by studying the transferable R plasmids and transposable elements. Here we describe the research on bacterial resistance to antibiotics in which many authors listed in the references have participated. The aspects of bacterial resistance dealt with are: (i) transferable resistance mediated by R plasmids in Gram-negative bacteria, (ii) R plasmid-mediated resistance to apramycin and hygromycin in clinical strains, (iii) the transposon Tn1696 and the integron In4, (iv) expression of Escherichia coli resistance genes in Haemophilus influenzae, (v) aminoglycoside-modifying-enzymes in the genus Mycobacterium with no relation to resistance, and (vi) macrolide-resistance and new mechanisms developed by Gram-positive bacteria.

Topics: Anti-Bacterial Agents; Cinnamates; DNA Transposable Elements; Drug Resistance, Microbial; Escherichia coli; Evolution, Molecular; Gram-Positive Bacteria; Haemophilus influenzae; Hygromycin B; Mycobacterium; Nebramycin; Plasmids

Owing to a striking, and most likely fortuitous, structural and sequence similarity with the bacterial 16 S ribosomal A site, the RNA kissing-loop complex formed by the HIV-1 genomic RNA dimerization initiation site (DIS) specifically binds 4,5-disubstituted 2-deoxystreptamine (2-DOS) aminoglycoside antibiotics. We used chemical probing, molecular modeling, isothermal titration calorimetry (ITC) and UV melting to investigate aminoglycoside binding to the DIS loop-loop complex. We showed that apramycin, an aminoglycoside containing a bicyclic moiety, also binds the DIS, but in a different way than 4,5-disubstituted 2-DOS aminoglycosides. The determination of thermodynamic parameters for various aminoglycosides revealed the role of the different rings in the drug-RNA interaction. Surprisingly, we found that the affinity of lividomycin and neomycin for the DIS (K(d) approximately 30 nM) is significantly higher than that obtained in the same experimental conditions for their natural target, the bacterial A site (K(d) approximately 1.6 microM). In good agreement with their respective affinity, aminoglycoside increase the melting temperature of the loop-loop interaction and also block the conversion from kissing-loop complex to extended duplex. Taken together, our data might be useful for selecting new molecules with improved specificity and affinity toward the HIV-1 DIS RNA.

Topics: 5' Untranslated Regions; Aminoglycosides; Anti-Bacterial Agents; Antiviral Agents; Binding Sites; Calorimetry; Cinnamates; Dimerization; HIV-1; Hygromycin B; Models, Molecular; Nebramycin; Nucleic Acid Conformation; Paromomycin; RNA, Viral; Thermodynamics