Old and new selective pressures on Mycobacterium tuberculosis

Abstract

Tuberculosis (TB) has been affecting humans for millennia. There is increasing indication that human-adapted Mycobacterium tuberculosis complex (MTBC) has been co-evolving with different human populations. Some of the most important drivers of MTBC evolution have been the host immune response and human demography. These old selective forces have shaped many of the features of human TB we see today. Two new selective pressures have emerged only a few decades ago, namely HIV co-infection and the use of anti-TB drugs. Here we discuss how the emergence of HIV/TB and drug resistance could impact the long-term balance between MTBC and its human host, and how these changes might influence the future evolutionary trajectory of MTBC.

Copyright © 2011 Elsevier B.V. All rights reserved.

Figures

Figure 1

Hypothetical representation of the infection and transmission dynamics of MTBC in HIV- positive (HIV+) and HIV-negative (HIV-) individuals. Transmission is represented by arrows. When transmission is impaired the arrow is interrupted by a cross. Different colours represent different MTBC genotypes; 1A - “Anybody can make it” hypothesis. 1B - “Superspreader” hypothesis with no transmission to HIV-negative individuals. 1C - “Superspreader” hypothesis with transmission to both HIV-negative and HIV-positive individuals