In the present work, we studied the genetic diversity of Mycobacterium tuberculosis clinical isolates from patients according to their gender, age, and geographic location in Mexico. We did not observe any statistically significant differences in regard to age or gender. We found that spoligo international type 53 (SIT53) is more frequent in the northern states and that SIT119 predominates in central Mexico. In a previous work, we described the spoligotype distribution in Nuevo León, Mexico, and reported that spoligo international type 53 (SIT53) and SIT119 were the most common spoligotypes to be isolated (representing ϳ39% of the total sample) (1). We also reported the tendencies of SIT53 to be isolated more frequently in elderly patients and of SIT119 to be isolated more frequently in younger patients (Ͻ20 years old). However, our sample size was too small to definitively support this conclusion. In the present work, we used a larger population sample to determine whether this difference is genuine and compared the distribution of spoligotypes in Nuevo León against those of the oldest and most densely populated region of Mexico, Mexico City, which has a population of ϳ30 million people.M. tuberculosis isolates (n ϭ 414) were obtained from the laboratories of either the Laboratorio Estatal de Salud Pública or the tuberculosis clinic at the Hospital Universitario, Dr. José E. Gonzalez UANL, Monterrey, Mexico, from 2001 to 2012. Because we observed a relationship between the distribution of spoligotypes and patient gender and age in a previous study, we included 233 new samples from Nuevo León; 116 cases were from patients 0 to 20 years old, and 117 cases were from patients Ͼ50 years old. From the Instituto Nacional de Enfermedades Respiratorias (INER) in Mexico City, we obtained 181 isolates from patients from several of Mexico's states, including Distrito Federal (n ϭ 126), Chiapas (n ϭ 10), Oaxaca (n ϭ 11), Veracruz (n ϭ 24), San Luis Potosí (n ϭ 1), Jalisco (n ϭ 1), and Michoacán (n ϭ 8).Isolates were obtained from any tuberculosis patient in the population and were grown on Lowenstein-Jensen medium. DNA isolation was performed using the method of van Embden et al. (2). Spoligotyping was accomplished using a standard technique as described previously (3).The spoligotypes were entered into the SITVIT2 database (Pasteur Institute of Guadeloupe) in a binary format. This database is an updated version of the previously released SpolDB4 database (see http://www.pasteur-guadeloupe.fr:8081/SITVIT_ONLINE).To establish differences in the spoligotype distribution among patients of different ages and genders, 233 samples corresponding to individuals who were either Ͻ30 or Ͼ60 years of age were analyzed. We observed a difference of 33% for SIT119 over SIT53 in the male patients, although this difference was not statistically significant. In the groups divided by age, we observed a 33% increase in the number of SIT119 spoligotypes in the younger patients; however, no significant differences were observed (Table 1). Final...