Tuberculosis: August 2006
Tuberculosis: August 2006
Verver S, Warren RM, Beyers N, et al. Rate of Reinfection Tuberculosis after Successful Treatment Is Higher than Rate of New Tuberculosis. Am J Respir Crit Care Med. 2005;171:1430- 1435. The study is from Cape Town, South Africa, and the goal of the study investigators was to determine the rate of recurrent tuberculosis (TB) that is attributed to reinfection after successful treatment.
Methods: Patients who had TB between 1993 and 1998 were followed through 2001 for disease requiring re-treatment (recurrent TB). Those with resistant strains or treatment failure were excluded. The analysis was limited to patients who had DNA fingerprinting of the Mycobacterium tuberculosis isolates.
Results: A total of 612 patients with baseline DNA fingerprinting were available for study. The median duration of follow-up was 5.2 years. Recurrent TB occurred in 108 patients (18%), including 61 with recurrence after successful treatment and 47 with recurrence after default. Of these 108 patients, 68 (63%) had DNA fingerprinting in the second episode. Of these, 24 of 31 recurrences (77%) after successful therapy were reinfections and 4 of 37 recurrences (11%) after default were reinfections. The reinfection rate after successful treatment was estimated at 2.2 per 100 person-years. These data are summarized in the Table .
Conclusions: The authors concluded that patients who have been treated successfully for TB are at higher risk for developing tuberculosis from reinfection compared with the general population. This specifically suggests that there may be a subgroup of patients who are intrinsically vulnerable to TB.
Comment: The concern I have with this conclusion is that the initial infection may have involved a mixed population of M. tuberculosis isolates. These results also raise the question of the potential for vaccine development if successful treatment of naturally occurring infection does not reduce susceptibility. These are obviously provocative issues that need to be worked out as we move forward with burgeoning interest in TB as the second most common microbial cause of death on earth.
Verver S, Warren RM, Beyers N, et al. Rate of Reinfection Tuberculosis after Successful Treatment Is Higher than Rate of New Tuberculosis. Am J Respir Crit Care Med. 2005;171:1430- 1435. The study is from Cape Town, South Africa, and the goal of the study investigators was to determine the rate of recurrent tuberculosis (TB) that is attributed to reinfection after successful treatment.
Methods: Patients who had TB between 1993 and 1998 were followed through 2001 for disease requiring re-treatment (recurrent TB). Those with resistant strains or treatment failure were excluded. The analysis was limited to patients who had DNA fingerprinting of the Mycobacterium tuberculosis isolates.
Results: A total of 612 patients with baseline DNA fingerprinting were available for study. The median duration of follow-up was 5.2 years. Recurrent TB occurred in 108 patients (18%), including 61 with recurrence after successful treatment and 47 with recurrence after default. Of these 108 patients, 68 (63%) had DNA fingerprinting in the second episode. Of these, 24 of 31 recurrences (77%) after successful therapy were reinfections and 4 of 37 recurrences (11%) after default were reinfections. The reinfection rate after successful treatment was estimated at 2.2 per 100 person-years. These data are summarized in the Table .
Conclusions: The authors concluded that patients who have been treated successfully for TB are at higher risk for developing tuberculosis from reinfection compared with the general population. This specifically suggests that there may be a subgroup of patients who are intrinsically vulnerable to TB.
Comment: The concern I have with this conclusion is that the initial infection may have involved a mixed population of M. tuberculosis isolates. These results also raise the question of the potential for vaccine development if successful treatment of naturally occurring infection does not reduce susceptibility. These are obviously provocative issues that need to be worked out as we move forward with burgeoning interest in TB as the second most common microbial cause of death on earth.
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