Infection of pregnant mice with Listeria monocytogenes induces fetal bradycardia.
BACKGROUND
Listeriosis is one of the most lethal bacterial diseases for fetuses and infants. However, pregnant women who get infected with Listeria may experience only mild symptoms, making the diagnosis difficult, even when the fetus is fatally infected.


METHODS
To reveal features of this infection, we conducted a multimodality imaging study of Listeria-induced miscarriage, using a pregnant mouse model. In this model, fetal morbidity and mortality can be observed in utero, noninvasively, and the timing and extent of infection can be carefully controlled. By employing in vivo bioluminescence imaging (BLI), perinatal infections were localized over time such that a correlation of infection to outcome could be determined without the need to kill the animal subject. The morbidity and viability of fetuses were assessed with ultrasound, and fetal morphology was imaged using magnetic resonance imaging (MRI).


RESULTS
The ultrasound revealed sustained fetal bradycardia, the slowing of the fetal heartbeat, in infected fetuses, with an association between slowed fetal heart rate and strong bioluminescent signal.


CONCLUSIONS
Uninfected fetuses showing no bioluminescent signal in the same uterine horn exhibited normal heartbeats. Thus, fetal bradycardia during infection was localized to the infected fetus and was not systemic or disseminated.
Department of Pediatrics, Stanford University School of Medicine, Stanford, California, USA. jonhardy@stanford.edu
Jonathan
J
Hardy
Brittani
B
Kirkendoll
Hui
H
Zhao
Laura
L
Pisani
Richard
R
Luong
Alexandra
A
Switzer
Michael V
MV
McConnell
Christopher H
CH
Contag
D000818:Animals; D001919:Bradycardia / Q000000981:diagnostic imaging / Q000209:etiology*; D004195:Disease Models, Animal; D005260:Female; D005315:Fetal Diseases / Q000000981:diagnostic imaging / Q000209:etiology*; D005327:Fetal Resorption; D008088:Listeriosis / Q000150:complications*; D008279:Magnetic Resonance Imaging; D051379:Mice; D011247:Pregnancy; D014463:Ultrasonography