SUMMARY SETTING Tuberculosis (TB) patients and their contacts enrolled in nine states and the District of Columbia from 16 December 2009 to 31 March 2011. OBJECTIVE To evaluate characteristics of TB patients that are predictive of tuberculous infection in their close contacts. DESIGN The study population was enrolled from a list of eligible African-American and White TB patients from the TB registry at each site. Information about close contacts was abstracted from the standard reports of each site. RESULTS Close contacts of African-American TB patients had twice the risk of infection of contacts of White patients (adjusted risk ratio [aRR] 2.1, 95%CI 1.3–3.4). Close contacts of patients whose sputum was positive for acid-fast bacilli on sputum smear microscopy had 1.6 times the risk of tuberculous infection compared to contacts of smear-negative patients (95%CI 1.1–2.3). TB patients with longer (>3 months) estimated times to diagnosis did not have higher proportions of infected contacts (aRR 1.2, 95%CI 0.9–1.6). CONCLUSION African-American race and sputum smear positivity were predictive of tuberculous infection in close contacts. This study did not support previous findings that longer estimated time to diagnosis predicted tuberculous infection in contacts.

Resistance and susceptibility to mycobacterial infection in the Biozzi high and low lines of mice which were genetically selected for their responses to heterologous erythrocytes have been found to be related to the innate ability of nonimmune macrophages to kill or inhibit the growth of the organisms during the first two weeks after infection and to their ability to mount specific and nonspecific immune responses. High antibody-producer mice were more capable of expressing cell-mediated immune parameters than low antibody-producer mice. A direct relationship was observed between the ability of bacteria (BCG vaccine) to multiply inside the reticuloendothelial system and the development of cell-mediated immunity, as measured by the delayed local reaction at the injection site, the lymphoproliferative response in the draining nodes, the tuberculin delayed-type hypersensitivity, the acquired resistance, and the adjuvant effect after BCG inoculation. In high line mice, apart from the inability of their macrophages to inhibit the early growth of bacteria, their lymphocytes in spleen and thymus were more capable of being stimulated in vitro by varying concentrations of living BCG. The data presented in this report are compatible with the hypothesis that a group of genes segregated in each line during the selective breeding controls the innate microbicidal activity.

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