Kinetics of Bartonella birtlesii infection in experimentally infected miceand pathogenic effect on reproductive functions

The kinetics of infection and the pathogenic effects on the reproductive fu nction of laboratory mice infected with Bartonella birtlesii recovered from an Apodemus species are described. B. birtlesii infection, as determined b y bacteremia, occurred in BALB/c mice inoculated intravenously. Inoculation with a low-dose inoculum (1.5 X 10(3) CFU) induced bacteremia in only 75% of the mice compared to all of the mice inoculated with higher doses (great er than or equal to1.5 X 10(4)). Mice became bacteremic for at least 5 week s (range, 5 to 8 weeks) with a peak ranging from 2 X 10(3) to 10(5) CFU/ml of blood. The bacteremia level was significantly higher in virgin females t han in males but the duration of bacteremia was similar. In mice infected b efore pregnancy (n = 20), fetal loss was evaluated by enumerating resorptio n and fetal death on day 18 of gestation. The fetal death and resorption pe rcentage of infected mice was 36.3% versus 14.5% for controls (P < 0.0001). Fetal suffering was evaluated by weighing viable fetuses. The weight of vi able fetuses was significantly lower for infected mice than for uninfected mice (P < 0.0002). Transplacental transmission of Bartonella was demonstrat ed since 76% of the fetal resorptions tested was culture positive for B. bi rtlesii. The histopathological analysis of the placentas of infected mice s howed vascular lesions in the maternal placenta, which could explain the re productive disorders observed. BALB/c mice appeared to be a useful model fo r studying Bartonella infection. This study provides the first evidence of reproductive disorders in mice experimentally infected with a Bartonella st rain originating from a wild rodent.