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Review
. 2022 Sep 15;10(9):1845.
doi: 10.3390/microorganisms10091845.

Evidence, Challenges, and Knowledge Gaps Regarding Latent Tuberculosis in Animals

Pamela Ncube  1 , Bahareh Bagheri  1 , Wynand Johan Goosen  1 , Michele Ann Miller  1 , Samantha Leigh Sampson  1
Affiliations
Review

Evidence, Challenges, and Knowledge Gaps Regarding Latent Tuberculosis in Animals

Pamela Ncube et al. Microorganisms. .

Abstract

Mycobacterium bovis and other Mycobacterium tuberculosis complex (MTBC) pathogens that cause domestic animal and wildlife tuberculosis have received considerably less attention than M. tuberculosis, the primary cause of human tuberculosis (TB). Human TB studies have shown that different stages of infection can exist, driven by host-pathogen interactions. This results in the emergence of heterogeneous subpopulations of mycobacteria in different phenotypic states, which range from actively replicating (AR) cells to viable but slowly or non-replicating (VBNR), viable but non-culturable (VBNC), and dormant mycobacteria. The VBNR, VBNC, and dormant subpopulations are believed to underlie latent tuberculosis (LTB) in humans; however, it is unclear if a similar phenomenon could be happening in animals. This review discusses the evidence, challenges, and knowledge gaps regarding LTB in animals, and possible host-pathogen differences in the MTBC strains M. tuberculosis and M. bovis during infection. We further consider models that might be adapted from human TB research to investigate how the different phenotypic states of bacteria could influence TB stages in animals. In addition, we explore potential host biomarkers and mycobacterial changes in the DosR regulon, transcriptional sigma factors, and resuscitation-promoting factors that may influence the development of LTB.

Keywords: Mycobacterium bovis; Mycobacterium tuberculosis; animal tuberculosis; domestic animals; host–pathogen interactions; latent tuberculosis; persister bacilli; phenotypic states; wildlife tuberculosis.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The authors declare that there are no conflict of interest.

Figures

Figure 1
Figure 1
Latent TB stage and underlying bacterial phenotypes. Latent TB is speculated to encompass several bacterial phenotypes, under the broad heading of persister bacteria. The subpopulations of persister bacilli include viable but non-replicating (VBNR) bacilli, viable but non-culturable VBNC bacilli, and dormant bacilli. These have varying phenotypic characteristics and may vary with each TB stage. (Original figure).
See this image and copyright information in PMC

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