Objective—To develop an aerosol exposure method
for induction of brucellosis in rhesus macaques
( Macaca mulatta ).
Animals—10 adult rhesus macaques.
Procedure—8 rhesus macaques were challenge
exposed with 102 to 105 colony-forming units of
Brucella melitensis 16M by use of an aerosol-exposure
technique, and 2 served as control animals. All
macaques were euthanatized 63 days after challenge
exposure. Gross and microscopic lesions, bacterial
burden in target organs, and histologic changes in tissues
Results—Grossly, spleen weights were increased in
exposed macaques, compared with spleen weights in
control macaques. Histologically, there was inflammation
in the liver, kidneys, spleen, testes, and epididymides
in exposed macaques. The spleen and
lymph nodes had increased numbers of lymphohistiocytic
cells. Morphometrically, the spleen also had an
increased ratio of white pulp to red pulp. Areas of
hepatitis and amount of splenic white pulp increased
with increasing exposure dose.
Conclusions and Clinical Relevance—Pathologic
findings in rhesus macaques after aerosol exposure
to B melitensis are similar to those observed in
humans with brucellosis.
Impact for Human Medicine—These results may aid
in the development of a vaccine against brucellosis that
can be used in humans. ( Am J Vet Res 2004;65:
Objective—To characterize effects of intranasal inoculation
of virulent Brucella melitensis strain 16M in
Animals—Female Balb/c mice, 6 to 8 weeks old.
Procedure—Studies were designed to elucidate
gross morphologic lesions, bacterial burden in target
organs, and histologic changes in tissues following
experimental intranasal inoculation of mice with B
melitensis 16M, which could be used to characterize
a model for testing vaccine efficacy.
Results—Measurable splenomegaly was evident at 3
and 7 weeks after inoculation. A demonstrable
increase in splenic colony-forming units (CFU) from
infected mice increased over time with increasing
dose when comparing inocula of 103, 104, and 105
CFU. Recovery of brucellae from the lungs was possible
early in infection with 101, 103, and 105 CFU, but
only the group inoculated with 105 CFU consistently
yielded quantifiable bacteria. At a dose of 101 CFU,
few organisms were located in the spleen. Bacteria
were recovered up to 140 days after inoculation in
mice given 103 CFU. At an inoculum of 105 CFU, bacterial
counts were highest early in infection.
Histologic examination of tissues revealed an
increase in white pulp and marginal zone in the
spleen and lymphohistiocytic hepatitis.
Conclusion and Clinical Relevance—Changes in the
spleen and liver increased with increases in dose and
with increased time following intranasal inoculation
with B melitensis 16M. Surprisingly, histologic
changes were not observed in the lungs of inoculated
mice. (Am J Vet Res 2001;62:398–405)