Etiology of human tuberculosis — Which bacteria can cause tuberculosis in humans, either classically or in specific epidemiologic settings?

Introduction / Context:
Tuberculosis (TB) in humans is primarily caused by Mycobacterium tuberculosis, but other members of the M. tuberculosis complex are also capable of producing disease in people, especially in particular geographic or zoonotic contexts. Awareness of these agents informs diagnosis, public health surveillance, and control strategies.

Given Data / Assumptions:

• M. tuberculosis complex includes M. tuberculosis, M. bovis, M. africanum, among others.
• Human infection may arise via inhalation (classical pulmonary TB) or, for M. bovis, via zoonotic transmission (e.g., unpasteurized dairy).
• Regional prevalence varies (e.g., M. africanum in parts of West Africa).

Concept / Approach:
While M. tuberculosis is the dominant global cause of human TB, M. bovis can infect humans (historically via dairy exposure) and M. africanum is an established human pathogen in certain regions. Therefore, all three listed organisms are recognized causes of human tuberculosis.

Step-by-Step Solution:

Verification / Alternative check:
Genotyping and lineage studies (e.g., spoligotyping, whole-genome sequencing) confirm relatedness and human pathogenicity across these species.

Why Other Options Are Wrong:

• Selecting a single species ignores the known zoonotic and regional contributors to human TB.

Common Pitfalls:
Equating all TB solely with M. tuberculosis; clinicians should consider M. bovis in relevant exposures and M. africanum in travelers or residents from endemic areas.

Final Answer:
All of these