The characteristics of tuberculosis (TB) patients related to a chain of recent TB transmissions were investigated.Mycobacterium tuberculosis (MTB) isolates (120) were genotyped using the restriction fragment length polymor-phism-IS6110 (R), spacer oligotyping (S) and mycobacterial interspersed repetitive units-variable number of tandemrepeats (M) methods. The MTB isolates were clustered and the clusters were grouped according to the similaritiesof their genotypes. Spearman’s rank correlation coefficients between the groups of MTB isolates with similar geno-types and those patient characteristics indicating a risk for a pulmonary TB (PTB) chain transmission were ana-lysed. The isolates showing similar genotypes were distributed as follows: SMR (5%), SM (12.5%), SR (1.67%), MR(0%), S (46.67%), M (5%) and R (0%). The remaining 35 cases were orphans. SMR exhibited a significant correlation(p < 0.05) with visits to clinics, municipalities and comorbidities (primarily diabetes mellitus). S correlated with drugconsumption and M with comorbidities. SMR is needed to identify a social network in metropolitan areas for PTBtransmission and S and M are able to detect risk factors as secondary components of a transmission chain of TB (PDF) Correlations between major risk factors and closely related Mycobacterium tuberculosis isolates grouped by three current genotyping procedures: A population-based study in northeast Mexico. Available from: