October 1, 2002
The proportion of patients with a well-documented first episode of tuberculosis (TB) who have a second recurrent episode is not well-known for unselected populations, and the proportion depends upon different socioeconomic conditions. Tuberculosis recurrences are assumed to be mainly due to mismanagement of the disease. Recurrences have traditionally been considered as endogenous reactivations of the strain that caused the primary episode. A few studies have found a role for reinfection in TB recurrences, always in selected high-risk groups of patients in whom reinfection is favored by specific epidemiological circumstance. The authors of this study searched for the rate of recurrent episodes of TB in a large unselected population not particularly prone to reinfection, during a 12-year period, and assessed the role of a new strain (reinfection) or the same strain (reactivation) in these recurrences.
In a 1,700-bed hospital that serves a population of 630,000 in Madrid, Spain, the authors reviewed the records of the mycobateriology laboratory from January 1, 1988, to December 31, 1999. All patients with 1 or more isolates of M tuberculosis in different respiratory clinical samples were considered. The authors considered patients with recurrent episodes, i.e. those with new isolates of M tuberculosis separated by more than 100 days from the primary episode. In patients selected with recurrent episodes, the authors collected information regarding sex, age, HIV status, TB therapy, duration of treatment, time between episodes, and physicians' opinion regarding individual adherence to therapy.
Overall, 172 patients had at least a second episode of TB more than 100 days apart. Ninety-two M tuberculosis sequential isolates from 43 patients with more than 1 episode were available for analysis. All the 92 strains were typed by spoligotyping. Forty-six different spoliogotypes were obtained for the whole analysis group. Of the 43 patients, 10 (23 percent) showed different strains for the first and second episodes, meaning reinfection was the cause of their recurrences. A second molecular typing method was performed for the 33 patients whose sequential isolates were considered indistinguishable. For 29 of the 33 patients identical strains were confirmed. The remaining four had different strains. If the data are taken together, reinfection was found in 14 (33 percent) of the 43 patients analyzed. Reactivations involving the same strain were found in the remaining 29 (67 percent) of the 43 patients.
After a lengthy discussion, the authors said, "In conclusion, our study shows a high proportion of TB recurrences caused by reinfection with a new strain. Reinfection in our analysis was found in a group of unselected patients and, therefore, they were not as homogeneous as others in previous reports. It was detected for HIV-positive and HIV-negative patients, in conditions in which high exposure was not expected and in patients who did not generally adhere to anti-TB treatment. Our data suggest that even when clinical/ epidemiological characteristics do not particularly favor reinfection, it should not be ruled out."
Archives of Internal Medicine
09.09.02; Vol. 162; No. 16: P. 1873-1879; Dario Garcia de Viedman, Ph.D.; Mercedes Marin, Pharm.D., Ph.D.; Susan Hernangómez, M.D.; Marisol Diaz, Pharm.D., Ph.D.; Maria Jesús Ruiz Serrano, Pharm.D.; Luis Alcalá, Pharm.D.; Emilio Bouza, M.D., Ph.D.