since the entire organ is generally homogenized and different
animals are sacrificed at each time point, lesion-specific responses
to TB treatment in the same animal can never be
assessed.
Furthermore, due to the lack of caseation in response
to TB—the hallmark of human disease—in the standard
mouse model, it may be essential to perform cross-species
studies of larger animal models, such as guinea pigs, rabbits, or
nonhuman primates, which develop microenvironments that
may be more relevant to human TB (12).
However, animal-to animal
variability is a more serious concern with these more
expensive species, which are generally not available as inbred
strains.
The need for noninvasive biomarkers to monitor disease
and response to treatment in the same group of animals
will be essential to conducting cost-effective studies of these
larger and more expensive species.