RESUMEN
Mutations in mprF have been shown to result in reduced susceptibility to daptomycin and other cationic antibacterials. An mprF antisense-inducible plasmid was constructed and used to demonstrate that depletion of mprF can reestablish susceptibility to daptomycin. Inducing antisense to mprF also resulted in increased susceptibility to vancomycin and gentamicin but, paradoxically, decreased susceptibility to oxacillin. These results suggest that mprF mutations that reduce susceptibility to cationic antibacterials result in a gain-of-function phenotype.
Asunto(s)
Antibacterianos/farmacología , Daptomicina/farmacología , Farmacorresistencia Bacteriana/genética , ARN sin Sentido/genética , Staphylococcus aureus/efectos de los fármacos , Staphylococcus aureus/genética , Proteínas Bacterianas/genética , Northern Blotting , Gentamicinas/farmacología , Pruebas de Sensibilidad Microbiana , Vancomicina/farmacologíaRESUMEN
Dihydrofolate reductase (DHFR) inhibitors such as trimethoprim (TMP) have long played a significant role in the treatment of bacterial infections. Not surprisingly, after decades of use there is now bacterial resistance to TMP and therefore a need to develop novel antibacterial agents with expanded spectrum including these resistant strains. In this study, we investigated the optimization of 2,4-diamnoquinazolines for antibacterial potency and selectivity. Using structure-based drug design, several 7-aryl-2,4-diaminoquinazolines were discovered that have excellent sub-100 picomolar potency against bacterial DHFR. These compounds have good antibacterial activity especially on gram-positive pathogens including TMP-resistant strains.
Asunto(s)
Antibacterianos/farmacología , Diseño de Fármacos , Inhibidores Enzimáticos/farmacología , Quinazolinas/farmacología , Staphylococcus aureus/efectos de los fármacos , Tetrahidrofolato Deshidrogenasa/metabolismo , Antibacterianos/síntesis química , Antibacterianos/química , Cristalografía por Rayos X , Relación Dosis-Respuesta a Droga , Inhibidores Enzimáticos/síntesis química , Inhibidores Enzimáticos/química , Pruebas de Sensibilidad Microbiana , Modelos Moleculares , Estructura Molecular , Quinazolinas/síntesis química , Quinazolinas/química , Estereoisomerismo , Relación Estructura-ActividadRESUMEN
Resistance to linezolid (LZD) occurs through mutations in 23S rRNA and ribosomal proteins L3 and L4 or through methylation of 23S rRNA by Cfr. Here we report novel L3 mutations, ΔSer145/His146Tyr and ΔMet169-Gly174, co-occurring with cfr in LZD-resistant Staphylococcus aureus isolates recovered from a hospital outbreak in Madrid, Spain. LZD MIC values (16, 32, or 64 µg/ml) correlated with the presence and severity of the L3 mutation. All isolates had TR-700 (torezolid) MIC values of ≤ 2 µg/ml.
Asunto(s)
Acetamidas/farmacología , Antiinfecciosos/farmacología , Proteínas Bacterianas/genética , Farmacorresistencia Bacteriana/genética , Metiltransferasas/metabolismo , Oxazolidinonas/farmacología , Proteínas Ribosómicas/genética , Staphylococcus aureus/efectos de los fármacos , Proteínas Bacterianas/química , Proteínas Bacterianas/metabolismo , Linezolid , Metiltransferasas/química , Metiltransferasas/genética , Pruebas de Sensibilidad Microbiana , Mutación , Proteína Ribosomal L3 , Proteínas Ribosómicas/química , Proteínas Ribosómicas/metabolismo , Staphylococcus aureus/enzimología , Staphylococcus aureus/genéticaRESUMEN
Staphylococcal resistance to linezolid (LZD) is mediated through ribosomal mutations (23S rRNA or ribosomal proteins L3 and L4) or through methylation of 23S rRNA by the horizontally transferred Cfr methyltransferase. To investigate the structural basis for oxazolidinone activity against LZD-resistant (LZD(r)) strains, we compared structurally diverse, clinically relevant oxazolidinones, including LZD, radezolid (RX-1741), TR-700 (torezolid), and a set of TR-700 analogs (including novel CD-rings and various A-ring C-5 substituents), against a panel of laboratory-derived and clinical LZD(r) Staphylococcus aureus strains possessing a variety of resistance mechanisms. Potency against all strains was correlated with optimization of C- and D-rings, which interact with more highly conserved regions of the peptidyl transferase center binding site. Activity against cfr strains was retained with either hydroxymethyl or 1,2,3-triazole C-5 groups but was reduced by 2- to 8-fold in compounds with acetamide substituents. LZD, which possesses a C-5 acetamide group and lacks a D-ring substituent, demonstrated the lowest potency against all strains tested, particularly against cfr strains. These data reveal key features contributing to oxazolidinone activity and highlight structural tradeoffs between potency against susceptible strains and potency against strains with various resistance mechanisms.
Asunto(s)
Acetamidas/farmacología , Proteínas Bacterianas/genética , Metiltransferasas/genética , Oxazolidinonas/farmacología , Ribosomas/genética , Staphylococcus aureus/efectos de los fármacos , Staphylococcus aureus/genética , Antibacterianos/farmacología , Linezolid , Pruebas de Sensibilidad Microbiana , Mutación , Staphylococcus aureus/enzimología , Relación Estructura-ActividadRESUMEN
Multiple inhibitors of the antibacterial target, Staphylococcus aureus MetRS, were identified by virtual screening. The process consisted of building a Catalyst pharmacophore from a ligand-S. aureus MetRS structure and using this pharmacophore to screen a commercial database. The top hits from this search were then docked into the S. aureus MetRS structure and this information was used to select compounds for testing. This resulted in a high hit rate of compounds that are in distinct structural classes from the known MetRS ligands.