title: Utility of Phenotypic and Genotypic Testing in the Study of Mycobacterium tuberculosis Resistance to First-Line Anti-Tuberculosis drugs.
abstract: OBJECTIVE
  To determine the utility of molecular techniques in the diagnosis of resistance and the extent of resistance to first-line drugs in our region.
  
  
  METHODS
  From 2004 to 2013, 1,889 strains of Mycobacterium tuberculosis complex isolated in Asturias, Spain, were studied using phenotypic (Clinical and Laboratory Standards Institute guidelines) and molecular (INNOLiPA RIF-TB©; GenotypeMDRplus©; GenotypeMDRsl©) sensitivity tests.
  
  
  RESULTS
  1,759 strains (94.52%) were sensitive to all first-line drugs, and 102 strains (5.48%) showed some resistance: 81 strains (4.35%) were resistant to 1 single drug, 14 (0.75%) were polyresistant, and 7 (0.37%) were multiresistant (resistant to rifampicin and isoniazid). In total, 137 resistances were identified: 60 to isoniazid (3.22%), 7 to rifampicin (0.37%), 9 to pyrazinamide (0.48%), 11 to ethambutol (0.59%), and 50 to streptomycin (2.68%). Of the mutations detected, 75.9% (63/83) correlated with resistance, while 24.09% of mutations detected (20/83) were not associated with resistance; 16 of these involved a silent mutation at codon 514 of the rpoB gene. Between 0 and 90% of strains, depending on the drug under consideration, were resistant even when no gene mutations were detected using marketed systems.
  
  
  CONCLUSIONS
  Molecular techniques are very useful, particularly for obtaining rapid results, but these must be confirmed with standard phenotypic sensitivity testing. The rate of resistance in our region is low and multi-drug resistantcases (0.37%) are sporadic.
authors.affiliation: Unidad de Referencia Regional de Micobacterias, Servicio de Microbiología, AGC Laboratorio de Medicina del HUCA, Oviedo, Asturias, España. Electronic address: luzmalba1@hotmail.com.
authors.forename: Luz María
authors.initials: LM
authors.lastname: Alba Álvarez
authors.affiliation: Unidad de Gestión Clínica de Neumología, Hospital San Agustín, Avilés, Asturias, España.
authors.forename: José María
authors.initials: JM
authors.lastname: García García
authors.affiliation: Servicio de Vigilancia y Alertas Epidemiológicas, Dirección General de Salud Pública, Consejería de Sanidad, Oviedo, Asturias, España.
authors.forename: M Dolores
authors.initials: MD
authors.lastname: Pérez Hernández
authors.affiliation: Unidad de Referencia Regional de Micobacterias, Servicio de Microbiología, AGC Laboratorio de Medicina del HUCA, Oviedo, Asturias, España.
authors.forename: Susana
authors.initials: S
authors.lastname: Martínez González
authors.affiliation: Unidad de Referencia Regional de Micobacterias, Servicio de Microbiología, AGC Laboratorio de Medicina del HUCA, Oviedo, Asturias, España.
authors.forename: Juan José
authors.initials: JJ
authors.lastname: Palacios Gutiérrez
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000995:Antitubercular Agents / Q000494:pharmacology*; D002648:Child; D002675:Child, Preschool; D024881:Drug Resistance, Bacterial; D005260:Female; D005838:Genotype; D006801:Humans; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000187:drug effects* / Q000235:genetics*; D010641:Phenotype; D011446:Prospective Studies; D055815:Young Adult
chemical_list: D000995:Antitubercular Agents
keywords: Epidemiology; Epidemiología; Molecular methods.; Métodos fenotípicos; Métodos moleculares; Phenotypic methods; Resistance; Resistencias; Tuberculosis