Resumen

AGAPITO, Juan, NEYRA, Víctor, CASTRO, Juan et al. Caracterización de las mutaciones en el gen rpoβ asociadas a la rifampicina en pacientes con tuberculosis pulmonar. Rev. perú. med. exp. salud publica, jul./set 2002, vol.19, no.3, p.117-123. ISSN 1726-4634.

Background: Rifampicin resistance in M. tuberculosis involves mutations in the rpoβ gene, encoding the β subunit of RNA polymerase. Objective: To identify the rpoβ gene mutations in strains of M. tuberculosis isolated from the Health Sub-Region in North Lima, Perϊ. Materials and methods: 73 sputum samples from patients with pulmonary tuberculosis were cultured on Lφwenstein-Jensen media. 62 samples, with more than 10 colonies per tube, were analyzed for susceptibility to isoniazid, streptomycin, rifampicin and ethambutol. DNA was isolated, amplified by PCR, followed by the cloning of the amplified product in the vector pGEM-T, transformation of competent E. coli bacteria, selection of recombinant clones and sequencing of the plasmid DNA for the determination of the polymorphisms in the rpoβ gene. Results: 52 strains out of 73 isolates (83,9%) were resistant to rifampicin (Rif r ), while 10 isolates (16,1%) were found to be rifampicin susceptible (Rif s ). 51 out of 52 Rif r strains contained mutations in the rpoβ gene associated with rifampicin resistance. 20 mutations were identified. The most frequently observed mutations were localized in the codons Ser-531 (62,7 %), His-526 (15,72%), Asp-516 (11,78%) and Gln-513 (5,88 %). No mutations were detected in the 10 Rif s strains. 94,2% of the Rif r strains were also resistant to isoniazid. Conclusions: rpoβ gene mutations associated with rifampicin resistance were present in almost all Rif r strains analyzed. Almost all Rif r strains were also resistant to isoniazid.

Palabras llave: Mycobacterium tuberculosis/genetics; Mycobacterium tuberculosis/drug effects; Tuberculosis drug resistant; Rifampin/diagnostic use; Peru.