Bacteriologic and histologic features in mice after intranasal inoculation of Brucella melitensis.
OBJECTIVE
To characterize effects of intranasal inoculation of virulent Brucella melitensis strain 16M in mice.


METHODS
Female Balb/c mice, 6 to 8 weeks old.


METHODS
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 10(3), 10(4), and 10(5) CFU. Recovery of brucellae from the lungs was possible early in infection with 10(1), 10(3), and 10(5) CFU, but only the group inoculated with 10(5) CFU consistently yielded quantifiable bacteria. At a dose of 10 CFU, few organisms were located in the spleen. Bacteria were recovered up to 140 days after inoculation in mice given 10(3) CFU. At an inoculum of 10(5) 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.


CONCLUSIONS
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.
Department of Diagnostic Pathology, Walter Reed Army Institute of Research, Silver Spring, MD 20910-7500, USA.
M G
MG
Mense
L L
LL
Van De Verg
A K
AK
Bhattacharjee
J L
JL
Garrett
J A
JA
Hart
L E
LE
Lindler
T L
TL
Hadfield
D L
DL
Hoover
D000281:Administration, Intranasal; D000818:Animals; D017347:Brucella melitensis / Q000472:pathogenicity*; D002006:Brucellosis / Q000382:microbiology / Q000473:pathology / Q000662:veterinary*; D004195:Disease Models, Animal; D005260:Female; D007091:Image Processing, Computer-Assisted; D007150:Immunohistochemistry / Q000662:veterinary; D008099:Liver / Q000382:microbiology / Q000473:pathology; D008168:Lung / Q000382:microbiology / Q000473:pathology; D051379:Mice; D008807:Mice, Inbred BALB C / Q000382:microbiology*; D013154:Spleen / Q000382:microbiology / Q000473:pathology; D013163:Splenomegaly / Q000382:microbiology / Q000473:pathology / Q000662:veterinary