Setting: Multidrug-resistant tuberculosis (MDR-TB) is a serious health problem in Eastern European countries, including Latvia.
Objective: To investigate the proportion of tuberculosis, including MDR-TB cases, attributable to recent transmission and risk factors associated with clustering.
Design: Retrospective nested case-control study. The data set incorporated a wide spectrum of social features, as well as genotypes of Mycobacterium tuberculosis isolates determined by insertion sequence 6110 restriction fragment length polymorphism analysis of PvuII cleaved genomic DNA and spoligotyping.
Results: In comparison with non-clustered M. tuberculosis, the Beijing genotype (OR 12.15) and multidrug resistance (OR 5.61, P < 0.01) were associated with clustering. In comparison with clustered drug-susceptible M. tuberculosis, clustering of MDR M. tuberculosis was associated with Beijing genotype (OR 41.67), previous hospitalisation (OR 18.33) and previous TB treatment (OR 17.68, P < 0.05). Direct epidemiological links in hospitals were found for almost one third (32%) of MDR Beijing cases.
Conclusions: MDR cases were more likely to be found in clusters than drug-susceptible cases (74.0% vs. 33.6%). Recent nosocomial transmission of MDR-TB is an important risk factor for the spread of multiresistance, and is associated with the Beijing genotype. Special attention should be paid to infection control measures in hospitals and ambulatory treatment should be enforced.