<i>In Vivo</i>and<i>Ex Vivo</i>Imaging Reveals a Long-Lasting Chlamydial Infection in the Mouse Gastrointestinal Tract following Genital Tract Inoculation

Intravaginal infection with Chlamydia muridarum in mice can ascend to the upper genital tract, resulting in hydrosalpinx, a pathological hallmark for tubal infertility in women infected with C. trachomatis. Here, we utilized in vivo imaging of C. muridarum infection in mice following an intravaginal inoculation and confirmed the rapid ascent of the chlamydial organisms from the lower to upper genital tracts. Unexpectedly, the C. muridarum-derived signal was still detectable in the abdominal area 100 days after inoculation. Ex vivo imaging of the mouse organs revealed that the long-lasting presence of the chlamydial signal was restricted to the gastrointestinal (GI) tract, which was validated by directly measuring the chlamydial live organisms and genomes in the same organs. The C. muridarum organisms spreading from the genital to the GI tracts were detected in different mouse strains and appeared to be independent of oral or rectal routes. Mice prevented from orally taking up excretions also developed the long-lasting GI tract infection. Inoculation of C. muridarum directly into the upper genital tract, which resulted in a delayed vaginal shedding of live organisms, accelerated the chlamydial spreading to the GI tract. Thus, we have demonstrated that the genital tract chlamydial organisms may use a systemic route to spread to and establish a long-lasting infection in the GI tract. The significance of the chlamydial spreading from the genital to GI tracts is discussed.