RESUMEN
OBJECTIVES: The aim of this study was to determine the in vitro activity of lipiarmycin against drug-resistant strains of Mycobacterium tuberculosis (MTB) and to establish the resistance mechanism of MTB against lipiarmycin using genetic approaches. METHODS: MIC values were measured against a panel of drug-resistant strains of MTB using the broth microdilution method. Spontaneous lipiarmycin-resistant mutants of MTB were tested for cross-resistance to standard anti-TB drugs, and their rpoB and rpoC genes were sequenced to identify mutations. RESULTS: Lipiarmycin exhibited excellent inhibitory activity against multidrug-resistant strains of MTB with MIC values of <0.1 mg/L. Sequence analysis of the rpoB and rpoC genes from spontaneous lipiarmycin-resistant mutants of MTB revealed that missense mutations in these genes caused resistance to lipiarmycin. Although both lipiarmycin and rifampicin are known to inhibit the bacterial RNA polymerase, the sites of mutation in the rpoB gene were found to be different in MTB strains resistant to these inhibitors. Whereas all six rifampicin-resistant MTB strains tested had mutation in the 81 bp hotspot region of the rpoB gene spanning codons 507-533, 16 of 18 lipiarmycin-resistant strains exhibited mutation between codons 977 and 1150. The remaining two lipiarmycin-resistant strains had mutation in the rpoC gene. CONCLUSIONS: Lipiarmycin has excellent bactericidal activity against MTB and lacks cross-resistance to standard anti-TB drugs. Furthermore, rifampicin-resistant strains remained fully susceptible to lipiarmycin, and none of the lipiarmycin-resistant MTB strains became resistant to rifampicin, highlighting the lack of cross-resistance.
Asunto(s)
Aminoglicósidos/farmacología , Antituberculosos/farmacología , ARN Polimerasas Dirigidas por ADN/antagonistas & inhibidores , Mycobacterium tuberculosis/efectos de los fármacos , Tuberculosis Resistente a Múltiples Medicamentos/microbiología , Adaptación Biológica , Secuencia de Aminoácidos , Sustitución de Aminoácidos/genética , Proteínas Bacterianas/genética , Análisis Mutacional de ADN , ADN Bacteriano/química , ADN Bacteriano/genética , Fidaxomicina , Humanos , Pruebas de Sensibilidad Microbiana , Viabilidad Microbiana , Modelos Moleculares , Datos de Secuencia Molecular , Mutación Missense , Mycobacterium tuberculosis/aislamiento & purificación , Rifampin/farmacología , Alineación de Secuencia , Análisis de Secuencia de ADNRESUMEN
PREMISE OF THE STUDY: The Million Orchid Project at Fairchild Tropical Botanic Garden is an initiative to propagate native orchids for reintroduction into Miami's urban landscapes. The aim of this study was to develop microsatellites for Encyclia tampensis and Cyrtopodium punctatum (Orchidaceae). METHODS AND RESULTS: Ten microsatellites were developed for each species. For E. tampensis sampled from the natural population, allele numbers ranged from one to four, with an average observed heterozygosity (H o) of 0.314 and average expected heterozygosity (H e) of 0.281. For the individuals from cultivation, allele numbers ranged from one to six, with an average H o of 0.35 and an average H e of 0.224. For C. punctatum, allele numbers ranged from one to three, with an average H o of 0.257 and an average H e of 0.272. CONCLUSIONS: These microsatellites will be used to assess the genetic diversity of natural and cultivated populations with the intention of guiding genetic breeding under the Million Orchid Project.