The new species Brucella microti replicates in macrophages and causes death in murine models of infection.
BACKGROUND
The recent isolation of Brucella microti from the common vole, the red fox, and the soil raises the possibility of an eventual reemergence of brucellosis in Europe. In this work, the pathogenic potential of this new Brucella species in both in vitro and in vivo models of infection was analyzed.


METHODS
The ability of B. microti (as compared to that of the closely related species Brucella suis) to replicate in human macrophages and in human and murine macrophage-like cells was determined. The behavior of B. microti and B. suis was evaluated in vivo in murine models of infection with Balb/c, CD1, and C57BL/6 mice.


RESULTS
B. microti showed an enhanced capacity for intramacrophagic replication compared with that of B. suis. Surprisingly, and in contrast to other species of Brucella, 10(5) colony-forming units of B. microti killed 82% of Balb/c mice within 7 days. Infection of spleen and liver with B. microti peaked at day 3, compared with B. suis infection, which peaked at day 7. Sublethal doses of B. microti induced good protection against a subsequent challenge with lethal doses.


CONCLUSIONS
In experimental cellular and murine infections, B. microti exhibited a high pathogenic potential, compared with other Brucella species.
Jiménez de Bagüés
María P
MP
Unidad de Sanidad Animal, Centro de Investigación y Tecnología Agroalimentaria, Gobierno de Aragón, Zaragoza, Spain.
Ouahrani-Bettache
Safia
S
Quintana
Juan F
JF
Mitjana
Olga
O
Hanna
Nabil
N
Bessoles
Stéphanie
S
Sanchez
Françoise
F
Scholz
Holger C
HC
Lafont
Virginie
V
Köhler
Stephan
S
Occhialini
Alessandra
A
D000818:Animals; D002002:Brucella / Q000145:classification* / Q000502:physiology*; D002006:Brucellosis / Q000276:immunology / Q000382:microbiology* / Q000401:mortality; D006801:Humans; D008099:Liver / Q000473:pathology; D008264:Macrophages / Q000382:microbiology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D009929:Organ Size; D013154:Spleen / Q000473:pathology