Mycobacterium tuberculosis Complex Genotype Diversity and Drug Resistance Profiles in a Pediatric Population in Mexico.

The aim of this study was to determine the frequency of drug resistance and the clonality of genotype patterns in M. tuberculosis clinical isolates from pediatric patients in Mexico (n = 90 patients from 19 states; time period-January 2002 to December 2003). Pulmonary disease was the most frequent clinical manifestation (71%). Children with systemic tuberculosis (TB) were significantly younger compared to patients with localized TB infections (mean 7.7 ± 6.2 years versus 15 ± 3.4 years P = 0.001). Resistance to any anti-TB drug was detected in 24/90 (26.7%) of the isolates; 21/90 (23.3%) and 10/90 (11.1%) were resistant to Isoniazid and Rifampicin, respectively, and 10/90 (11.1%) strains were multidrug-resistant (MDR). Spoligotyping produced a total of 55 different patterns; 12/55 corresponded to clustered isolates (n = 47, clustering rate of 52.2%), and 43/55 to unclustered isolates (19 patterns were designated as orphan by the SITVIT2 database). Database comparison led to designation of 36 shared types (SITs); 32 SITs (n = 65 isolates) matched a preexisting shared type in SITVIT2, whereas 4 SITs (n = 6 isolates) were newly created. Lineage classification based on principal genetic groups (PGG) revealed that 10% of the strains belonged to PGG1 (Bovis and Manu lineages). Among PGG2/3 group, the most predominant clade was the Latin-American and Mediterranean (LAM) in 27.8% of isolates, followed by Haarlem and T lineages. The number of single drug-resistant (DR) and multidrug-resistant (MDR-TB) isolates in this study was similar to previously reported in studies from adult population with risk factors. No association between the spoligotype, age, region, or resistance pattern was observed. However, contrary to a study on M. tuberculosis spoligotyping in Acapulco city that characterized a single cluster of SIT19 corresponding to the EAI2-Manila lineage in 70 (26%) of patients, not a single SIT19 isolate was found in our pediatric patient population. Neither did we find any shared type belonging to the EAI family which represents ancestral PGG1 strains within the M. tuberculosis complex. We conclude that the population structure of pediatric TB in our setting is different from the one prevailing in adult TB patient population of Guerrero.

Comparison among three methods for mycobacteria identification

Objetivo. Comparar tres métodos: pruebas bioquímicas, cromatografía líquida de alta resolución (HPLC, por sus siglas en inglés) y reacción en cadena de la polimerasa-polimorfismo del tamaño de fragmentos de restricción (PCR-RFLP) para identificar micobacterias a nivel especie, analizando costo-beneficio y proponiendo un algoritmo de identificación. Material y métodos. Entre febrero de 1999 y enero de 2000, en los laboratorios del Instituto de Diagnóstico y Referencia Epidemiológicos se tipificaron 107 aislados de micobacterias y los resultados se compararon con los obtenidos en un laboratorio de referencia utilizando la prueba estadística Q de Cochran. Resultados. Se encontró que el PCR-RFLP fue el método más específico y rápido pero también el más caro. Las pruebas bioquímicas fueron confiables para la identificación de Mycobacterium tuberculosis, pero lentas e inespecíficas para otras micobacterias. El HPLC estuvo en un nivel medio tomando en cuenta costo, tiempo y especificidad. Conclusiones. Considerando la proporción esperada de M. tuberculosis, se propone el siguiente algoritmo: si las pruebas bioquímicas indican una micobacteria no tuberculosa, el aislado será analizado por HPLC; si la identificación no es clara, el aislado será analizado usando PCR-RFLP. Si el aislado no pertenece a un patrón descrito, se identificará por secuenciación de ADN.