rrs and rpsL mutations in streptomycin-resistant isolates ofMycobacterium tuberculosis from Mexico
Betzaida Cuevas-Córdoba, Aremy Cuellar-Sánchez, Aurora Pasissi-Crivelli, Carlos Armando Santana-Álvarez, Javier Hernández-Illezcas, Roberto Zenteno-Cuevas
Received: May 5, 2012 Revised: April 20, 2012 Accepted: May 31, 2012
Corresponding author. Roberto Zenteno-Cuevas, Instituto de Salud Pública, Universidad Veracruzana, Av. Luis Castelazo Ayala s/n, A.P. 57. Col. Industrial Animas, Xalapa, Veracruz 91190, Mexico.
Background and purpose:
Mycobacteria were isolated from patients with suspected drug-resistant tuberculosis. Susceptibility tests were carried out using the fluorometric method, and rrs and rpsL DNA sequencing was performed by capillary electrophoresis.
Some 136 drug-resistant isolates were recovered, of which 91(67%) exhibited resistance to streptomycin. Mutations in rpsLwere observed in 18 isolates (19%) in codons 43 (A→G, K/R, n = 12) and 88 (A→G, K/R, n = 4; A→C, K/Q, n = 2). Mutations inrrs were observed in 26 isolates (28%). These were at nucleotides 513 (A→C, n = 8) and 516 (C→T, n = 6), and six novel mutations at nucleotides 483 (A→T, n = 2), 485 (A→G, n = 2), 496 (G→A, n = 2), 795 (C→T, n = 6), 870 (C→T, n = 3), and 907 (A→C, n = 3), with some isolates showing more than one mutation. Finally, 47 (52%) of the isolates showed no mutation.
The variety and presence or absence of the mutations found suggest the circulation of an important diversity of strains and the existence of additional mechanisms contributing to streptomycin resistance in the region.
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