title: rrs and rpsL mutations in streptomycin-resistant isolates of Mycobacterium tuberculosis from Mexico.
abstract: OBJECTIVE
  Mutations in rpsL and rrs genes are associated with resistance to streptomycin in tuberculosis, but important geographical variation exists in these mutations. The goal of this study was to characterize these mutations in isolates of streptomycin-resistant mycobacteria originating from southeast Mexico.
  
  
  METHODS
  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.
  
  
  RESULTS
  Some 136 drug-resistant isolates were recovered, of which 91(67%) exhibited resistance to streptomycin. Mutations in rpsL were 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 in rrs 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Laboratorio de Ecología y Salud, Instituto de Salud Pública, Universidad Veracruzana, Veracruz, Mexico.
authors.forename: Betzaida
authors.initials: B
authors.lastname: Cuevas-Córdoba
authors.forename: Aremy
authors.initials: A
authors.lastname: Cuellar-Sánchez
authors.forename: Aurora
authors.initials: A
authors.lastname: Pasissi-Crivelli
authors.forename: Carlos Armando
authors.initials: CA
authors.lastname: Santana-Álvarez
authors.forename: Javier
authors.initials: J
authors.lastname: Hernández-Illezcas
authors.forename: Roberto
authors.initials: R
authors.lastname: Zenteno-Cuevas
mesh_terms: D000328:Adult; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D005260:Female; D014644:Genetic Variation; D006801:Humans; D008297:Male; D008800:Mexico; D008875:Middle Aged; D009154:Mutation; D009169:Mycobacterium tuberculosis / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification; D012336:RNA, Ribosomal, 16S / Q000235:genetics*; D012269:Ribosomal Proteins / Q000235:genetics*; D013307:Streptomycin / Q000494:pharmacology*; D018088:Tuberculosis, Multidrug-Resistant / Q000382:microbiology
chemical_list: D000900:Anti-Bacterial Agents; D012336:RNA, Ribosomal, 16S; D012269:Ribosomal Proteins; C034212:ribosomal protein S12; D013307:Streptomycin