RESUMEN
The risk of acquiring additional drug resistance in strains of multidrug-resistant tuberculosis (MDR-TB) during failure of empiric standardized retreatment regimens is poorly defined. We sought to estimate this risk by comparing drug susceptibility profiles and RFLP patterns of paired MDR-TB isolates collected from 27 patients before and after retreatment failure. Among 23 patients with paired isolates with concordant RFLP patterns, 19 (83%) had become resistant to at least one additional drug after failed retreatment. In this limited group of MDR-TB patients, acquisition of resistance was common during failure of empiric drug regimens. Further study is needed to confirm these findings.
Asunto(s)
Antituberculosos/uso terapéutico , Terapia por Observación Directa , Tuberculosis Resistente a Múltiples Medicamentos/tratamiento farmacológico , Adolescente , Adulto , Antituberculosos/farmacología , Femenino , Humanos , Masculino , Pruebas de Sensibilidad Microbiana , Persona de Mediana Edad , Polimorfismo de Longitud del Fragmento de Restricción , Retratamiento , Tuberculosis Resistente a Múltiples Medicamentos/microbiologíaRESUMEN
In many developing countries and outside hospital settings, the characteristics of endemic Mycobacterium tuberculosis strains resistant to multiple drugs remain unknown. In a community-based referral and therapy program in northern Lima, Peru, beginning in 1996, patients found to be failures on standard regimens were referred for drug-susceptibility testing of their isolates, and those found to be infected with M. tuberculosis isolates resistant to at least rifampin were treated with individualized regimens based on their infecting strains. Isolates from 42 of these patients were subjected to DNA sequencing of the rpoB gene region responsible for rifampin resistance. We determined the frequency of types of mutations in the rpoB gene among these Peruvian isolates.
Asunto(s)
Antibióticos Antituberculosos/farmacología , ARN Polimerasas Dirigidas por ADN/genética , Mutación , Mycobacterium tuberculosis/efectos de los fármacos , Rifampin/farmacología , Farmacorresistencia Microbiana/genética , Humanos , Mycobacterium tuberculosis/genética , Mycobacterium tuberculosis/aislamiento & purificación , Perú/epidemiología , Análisis de Secuencia de ADN , Tuberculosis Pulmonar/microbiologíaRESUMEN
Interactions between the dephosphorylated regulatory light chains (RLCs) of smooth muscle myosin are involved in maintaining the enzymatically "off" state. Expressed chimeric smooth muscle heavy meromyosins containing skeletal muscle myosin heavy chain (HC) sequences were used to assess the relative importance of the light chain-binding domain (or "neck") to regulation. Surprisingly, regulation remained intact with a skeletal RLC-binding site. A chimera with the entire alpha-helical neck composed of skeletal HC sequence showed 2-fold regulation of motility and nearly 5-fold regulation of actin-activated ATPase activity. Complete activation of the dephosphorylated state (i.e. complete loss of regulation) occurred when skeletal HC sequence extended from the head/rod junction to the SH1-SH2 helix. Smooth muscle-specific sequences near the motor domain may therefore position the regulatory domain in a way that optimizes RLC-rod-head interactions, thus enabling a completely off state when the RLC is dephosphorylated. Conversely, a chimera that joins the motor domain from unconventional myosin V to the smooth muscle myosin neck and rod showed only 2-fold regulation. The presence of the smooth muscle light chain-binding region and rod is therefore not sufficient to confer complete phosphorylation-dependent regulation upon all motor domains of the myosin family.
Asunto(s)
Músculo Liso/metabolismo , Cadenas Pesadas de Miosina/metabolismo , Cadenas Ligeras de Miosina/metabolismo , Subfragmentos de Miosina/metabolismo , Secuencia de Aminoácidos , Animales , Sitios de Unión , Línea Celular , Ratones , Modelos Moleculares , Datos de Secuencia Molecular , Músculo Esquelético/química , Músculo Esquelético/metabolismo , Músculo Liso/química , Cadenas Pesadas de Miosina/genética , Cadenas Ligeras de Miosina/genética , Subfragmentos de Miosina/genética , Miosinas/metabolismo , Proteínas Recombinantes de Fusión/metabolismo , Spodoptera , Relación Estructura-ActividadRESUMEN
Uncoupler resistance presents a potential challenge to the conventional chemiosmotic coupling mechanism. In E. coli, an adaptive response to uncouplers was found in cell growing under conditions requiring oxidative phosphorylation. It is suggested that uncoupler-resistant mutants described in the earlier literature might represent a constitutive state of expression of this "low energy shock" adaptive response. In the environment, bacteria are confronted by nonclassical uncoupling factors such as organic solvents, heat, and extremes of pH. It is suggested that the low energy shock response will aid the cell in coping with the effects of natural uncoupling factors. The genetic analysis of uncoupler resistance has only recently began, and is yielding interesting and largely unexpected results. In Bacillus subtilis, a mutation in fatty acid desaturase causes an increased content of saturated fatty acids in the membrane and increased uncoupler resistance. The protonophoric efficiency of uncouplers remains unchanged in the mutants, inviting nonorthodox interpretations of the mechanism of resistance. In E. coli, two loci conferring resistance to CCCP and TSA were cloned and were found to encode multidrug resistance pumps. Resistance to one of the uncouplers, TTFB, remained unchanged in strains mutated for the MDRs, suggesting a resistance mechanism different from uncoupler extrusion.
Asunto(s)
Bacterias/efectos de los fármacos , Fenómenos Fisiológicos Bacterianos , Farmacorresistencia Microbiana , Desacopladores/farmacología , Bacillus subtilis/efectos de los fármacos , Bacillus subtilis/fisiología , Carbonil Cianuro m-Clorofenil Hidrazona/farmacología , Membrana Celular/metabolismo , Escherichia coli/efectos de los fármacos , Escherichia coli/fisiología , Bacterias Gramnegativas/efectos de los fármacos , Bacterias Gramnegativas/fisiología , Modelos Biológicos , Ósmosis , Bombas de Protones/efectos de los fármacos , Bombas de Protones/metabolismo , Sodio/metabolismo , Relación Estructura-ActividadRESUMEN
E. coli adapt to uncouplers in the presence of a non-fermentable carbon source. Adaptation is accompanied by the restoration of the proton motive force and ATP. A collection of uncoupler-sensitive Tn,lacZ,kan fusion strains was obtained by ampicillin enrichment in the presence of TSA. One of the fusion strains was induced by uncouplers. The fusion gene emrD was mapped to min. 83.1, cloned and sequenced. EmrD is a member of the major facilitator family of pmf-dependent translocases and is homologous to a number of bacterial multidrug resistance pumps. Resistance to some uncouplers including TTFB was not affected by emrD, and growth recovery to this uncoupler was very sluggish. It is suggested that EmrD is a new bacterial multidrug resistance pump that participates in a low energy shock adaptive response.