La tubercolosi ricorrente : recidiva o reinfezione esogena?

Recurrent tuberculosis (TB) is an issue that makes worldwide eradication of the disease difficult, especially in countries with a high incidence of TB. Recurrent TB may be due to relapse of the original episode or to an exogenous reinfection caused by a different strain of Mycobacterium tuberculosis. We performed a meta-analysis of selected studies on recurrent TB from 2000 to 2013, adopting molecular genotyping to discriminate between exogenous reinfection and relapses, in order to specifically evaluate the role of HIV infection in the origin of recurrence. Comparison among the studies was limited by the population heterogeneity of the different studies in terms of epidemiology, health status, and diagnostic and therapeutic approach. However, exogenous reinfections are more common in high-burden countries, where HIV infection plays a major role in increasing the risk of a new infection. In contrast, this finding was not confirmed in low-burden countries. Vice versa, globally recognized factors for TB relapse were low compliance to anti-tuberculous treatment,multidrug resistance and persistence of cavitations in the lung parenchyma. The role of other factors like social conditions (immigration, homelessness, working conditions),co-morbidities (silicosis), and characteristics of anti-TB treatment is still controversial.