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Derivation of the study population for genotypic cluster analysis, San Francisco, 1991–2002. Boxes to the right indicate exclusions leading to a study population of 2,193 patients with genotyped isolates. We excluded 25 patients whose isolates were laboratory contaminants, 11 cases of Mycobacterium bovis, and 2 patients who were treated with bacille Calmette-Guèrin (BCG). RFLP = restriction fragment-length polymorphism.
