Utilidad de los métodos fenotípicos y genotípicos en el estudio de resistencias de Mycobacterium tuberculosis a fármacos antituberculosos de primera línea / Utility of phenotypic and genotypic testing in the study of Mycobacterium tuberculosis resistance to first-line anti-tuberculosis drugs

Objetivo: Conocer la utilidad de las técnicas moleculares para el diagnóstico de resistencias y la situación de las resistencias a fármacos de primera línea en nuestra área geográfica. Material y método: Desde 2004 a 2013, 1.889 cepas de Mycobacterium tuberculosis complex aisladas en Asturias, España, fueron estudiadas mediante pruebas de sensibilidad fenotípicas (directrices del Clinical and Laboratory Standards Institute) y moleculares (INNOLiPA RIF-TB©; GenotypeMDRplus©; GenotypeMDRsl©). Resultados: Mil setecientas cincuenta y nueve cepas (94,52%) eran sensibles a todos los fármacos de primera línea y 102 cepas (5,48%) presentaban alguna resistencia: 81 cepas (4,35%) a un solo fármaco, 14 (0,75%) con polirresistencia y 7 (0,37%) multirresistentes (resistencia a rifampicina e isoniacida). En total hubo 137 resistencias a fármacos: 60 a isoniacida (3,22%), 7 a rifampicina (0,37%), 9 a pirazinamida (0,48%), 11 a etambutol (0,59%) y 50 a estreptomicina (2,68%). El 75,9% de las mutaciones detectadas (63/83) se correlacionaron con resistencia; mientras que un 24,09% de las mutaciones detectadas (20/83) no implicaban resistencia, correspondiendo 16 a una mutación silente en el codón 514 del gen rpoB. Entre un 0 y un 90% de cepas, dependiendo del fármaco que se considere, eran resistentes aunque no presentaban mutaciones en los genes incluidos en los sistemas comerciales. Conclusiones: Las técnicas moleculares resultan muy útiles sobre todo por la rapidez en la obtención de resultados, aunque estos deben confirmarse con las pruebas de sensibilidad fenotípicas de referencia. La tasa de resistencias a fármacos en nuestra región es baja y los casos de multirresistencia (0,37%) son esporádicos

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. Material and method: 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 resistant cases (0.37%) are sporadic

Utility of Phenotypic and Genotypic Testing in the Study of Mycobacterium tuberculosis Resistance to First-Line Anti-Tuberculosis drugs. / Utilidad de los métodos fenotípicos y genotípicos en el estudio de resistencias de Mycobacterium tuberculosis a fármacos antituberculosos de primera línea.

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. MATERIAL AND METHOD: 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.

Molecular and epidemiological population-based integrative analysis of human and animal Mycobacterium bovis infections in a low-prevalence setting.

Human Mycobacterium bovis infections are considered to be due to reactivations, when involve elderly people, or to recent transmissions, when exposure is occupational. We determined the cause of M. bovis infections by genotyping M. bovis isolates in a population-based study integrating human and animal databases. Among the 1,586 tuberculosis (TB) cases in Asturias, Northern Spain (1,080,000 inhabitants), 1,567 corresponded to M. tuberculosis and 19 to M. bovis. The number of human isolates sharing genotype with cattle isolates was higher than expected (47%) for a setting with low prevalence of bovine TB and efficient control programs in cattle. The risk of exposure to infected animals was probable/possible in most of these matched cases (77.7%). Recent transmission was the likely explanation of most M. bovis infections in elderly people. A potential human-to-human transmission was found. Our study illustrates a model of collaboration between human and animal health professionals to provide a precise snapshot of the transmission of M. bovis in the human-animal interface.