Resultados: Se identificaron cinco tipos de mutaciones diferentes en el gen rpoB. La mutación Ser531*Leu se detectó en 14 cepas (66,7%), la mutación H526*Asp en 3 cepas (14,3%), Asn518*Ser en una cepa (4,8%), Glu513*Leu en una cepa (4,8%). En una cepa (4,8%) se detectó una deleción de 9 nucleótidos del codón 510 al 513, mientras que en la cepa restante (4,8%) no se detectó ninguna mutación.
Conclusiones: La distribución y frecuencia de mutaciones en las cepas de M. tuberculosis resistentes a rifampicina son similares a las publicadas. Sin embargo, hemos detectado dos mutaciones en el gen rpoB no descritas previamente: la deleción de 9 nucleótidos (510-513) y la mutación puntual Asn518*Ser. La identificación de todas estas mutaciones podría utilizarse como marcador epidemiológico de los aislamientos clínicos
Methods: Characterization of rpoB mutations in 21 rifampicin-resistant strains of M. tuberculosis isolated during a three-year period (1994-1996) by three different molecular methods: a nonradiactive Single-strand conformation polymorphism (SSCP) analysis, DNA sequence analysis and a commercial method the line probe assay InnoLiPA.
Results: Five distinct rpoB mutations were identified. Ser531*Leu mutation was detected in 14 strains (66.7%), H526*Asp in 3 strains (14.3%), Ans518*Ser in 1 strain (4.8%), Glu513*Leu in 1 strain (4.8%). A nine nucleotide deletion (codon 510-513) was found in one strain (4.8%) while in the remaining resistant strain (4.8%) no mutation was detected.
Conclusions.: The frecuency of the different mutations found in the rpoB gene, associated with rifampicin resistance in Mycobacterium tuberculosis clinical isolates in Sevilla, are similar to those previously reported. However, two new mutations has been detected: a nine nucleotide deletion (codon 510-513), and the Asn518*Ser point mutation. The characterization of the mutations in the rpoB gene could serve as epidemiological marker for the rifampicin resistant clinical isolates of M. tuberculosis.