RESUMO
Despite advances, tuberculosis remains a significant infectious disease, whose mortality presents alarming numbers. Although it can be cured, the number of cases of antimicrobial resistant strains is increasing, requiring the use of less efficient second-line drugs. Capreomycin and streptomycin are part of this group, being antibiotics whose mechanism of action is the inhibition of protein synthesis when interacting with the tuberculosis bacterial ribosome. Their binding mechanisms are distinct: capreomycin is able to bind to both ribosomal (30S and 50S) subunits, whereas streptomycin binds only to the smaller one (30S). In this context, the biochemical characterization of these binding sites for a proper understanding of their complex interactions is of crucial importance to increase their efficacy. Through crystallographic data and computer simulations, in this work we calculated the interaction binding energies of capreomycin and streptomycin in complex with the tuberculosis bacterial ribosome subunits, by using density functional theory (DFT) within the molecular fractionation with conjugated caps (MFCC) approach. For capreomycin in the 30S (50S) subunit, we investigated the binding energies of 44 (30) residues presented within a pocket radius of 14 Å (30 Å). Regarding streptomycin, 60 nucleotide (25 amino acid) residues distributed up to 12.5 Å (15 Å) away from the drug in the 30S subunit (S12 protein) were taken into account. We also identify the contributions of hydrogen bonds and hydrophobic interactions in the drug-receptor complex, and the regions of the drugs that most contributed to the anchorages of them in their binding sites, as well as identify residues that are most associated with mutations.
Assuntos
Antibacterianos/química , Capreomicina/química , Metabolismo Energético , Mycobacterium tuberculosis/metabolismo , Subunidades Ribossômicas/química , Subunidades Ribossômicas/metabolismo , Estreptomicina/química , Antibacterianos/metabolismo , Antibacterianos/uso terapêutico , Capreomicina/metabolismo , Capreomicina/uso terapêutico , Simulação por Computador , Cristalização , Humanos , Mutação , Mycobacterium tuberculosis/química , Receptores de Droga/genética , Receptores de Droga/metabolismo , Estreptomicina/metabolismo , Estreptomicina/uso terapêutico , Tuberculose/tratamento farmacológico , Tuberculose/microbiologiaRESUMO
Biofilms formed on implanted devices are difficult to eradicate. Adhesion mechanism, high bacterial density, aggregation, induction of persisters and stressed bacteria are some of the factors considered when the antimicrobial resistance of these biofilms is analyzed. The aim of this work was to provide an alternative approach to the understanding of this issue by using a specially designed experimental set up that includes the use of microstructured (MS) surfaces (potential inhibitors of bacterial aggregation) in combination with antimicrobial agents (streptomycin and levofloxacin) against Staphylococcusaureus attached cells. Biofilms formed on smooth surfaces were used as plain controls (biofilmed-PC) characterized by the formation of dense 2D bacterial aggregates. Results showed bacterial persistence when streptomycin or levofloxacin were applied to PC-biofilms. The antimicrobial activity of both antibiotics was enhanced when bacteria were attached on MS, where single cells or small aggregates were observed. Thus, dense 2D aggregates of bacteria seem to be crucial as a required previous stage to develop the antimicrobial resistance.
Assuntos
Aderência Bacteriana/efeitos dos fármacos , Biofilmes/crescimento & desenvolvimento , Farmacorresistência Bacteriana/efeitos dos fármacos , Levofloxacino , Staphylococcus aureus/fisiologia , Estreptomicina , Biofilmes/efeitos dos fármacos , Levofloxacino/química , Levofloxacino/farmacologia , Estreptomicina/química , Estreptomicina/farmacologiaRESUMO
The interactions of L-aminoglucosidic stereoisomers such as rhodostreptomycins A (Rho A) and B (Rho B) with cations (Mg(2+), Ca(2+), and H(+)) were studied by a quantum mechanical method that utilized DFT with B3LYP/6-311G. Docking studies were also carried out in order to explore the surface recognition properties of L-aminoglucoside with respect to Mg(2+) and Ca(2+) ions under solvated and nonsolvated conditions. Although both of the stereoisomers possess similar physicochemical/antibiotic properties against Helicobacter pylori, the thermochemical values for these complexes showed that its high affinity for Mg(2+) cations caused the hydration of Rho B. According to the results of the calculations, for Rho A-Ca(2+)(H2O)6, ΔH = -72.21 kcal mol(-1); for Rho B-Ca(2+)(H2O)6, ΔH = -72.53 kcal mol(-1); for Rho A-Mg(2+)(H2O)6, ΔH = -72.99 kcal mol(-1) and for Rho B-Mg(2+)(H2O)6, ΔH = -95.00 kcal mol(-1), confirming that Rho B binds most strongly with hydrated Mg(2+), considering the energy associated with this binding process. This result suggests that Rho B forms a more stable complex than its isomer does with magnesium ion. Docking results show that both of these rhodostreptomycin molecules bind to solvated Ca(2+) or Mg(2+) through hydrogen bonding. Finally, Rho B is more stable than Rho A when protonation occurs.
Assuntos
Cátions Bivalentes/química , Magnésio/química , Estreptomicina/análogos & derivados , Cálcio/química , Ligação de Hidrogênio , Modelos Moleculares , Simulação de Acoplamento Molecular , Teoria Quântica , Estereoisomerismo , Estreptomicina/química , TermodinâmicaRESUMO
Pasteurised bovine milk from retail markets in the State of São Paulo, Brazil, was analysed for the presence of streptomycin (STP) and dihydrostreptomycin (DHSTP) residues. An ELISA kit was used for screening and a LC-APCI-MS/MS QToF method for confirmatory analysis. Both methods were intra-laboratory validated and found suitable for screening and confirmatory testing, respectively, for STP and DHSTP residues in pasteurised bovine milk at concentration levels below the maximum residue limit (MRL) established for these substances (200 µg kg(-1) expressed as the sum of the concentrations of STP and DHSTP). No residues of STP and DHSTP at detectable levels were found in the analysed samples (n = 299).