Chlamydia Spreads to the Large Intestine Lumen via Multiple Pathways

Abstract

Chlamydia in the genital tract is known to spread via the blood circulation system to the large intestine lumen to achieve long-lasting colonization. However, the precise pathways by which genital Chlamydia accesses the large intestine lumen remain unclear. The spleen was recently reported to be critical for chlamydial spreading. In the current study, it was found that following intravaginal inoculation with Chlamydia, mice with and without splenectomy both yielded infectious Chlamydia on rectal swabs, indicating that the spleen is not essential for genital Chlamydia to spread to the gastrointestinal tract. This conclusion was validated by the observation that intravenously inoculated Chlamydia was also detected on the rectal swabs of mice regardless of splenectomy. Careful comparison of the tissue distribution of live chlamydial organisms following intravenous inoculation revealed redundant pathways by which Chlamydia can reach the large intestine lumen. The intravenously inoculated Chlamydia was predominantly recruited to the spleen within 12 h and then detected in the stomach lumen by 24 h, in the intestinal lumen by 48 h, and on rectal swabs by 72 h. These observations suggest a potential spleen-to-stomach pathway for hematogenous Chlamydia to reach the large intestine lumen. This conclusion was supported by the observation made in mice under coprophagy-free condition. However, in the absence of spleen, hematogenous Chlamydia was predominantly recruited to the liver and then simultaneously detected in the intestinal tissue and lumen, suggesting a potential liver-to-intestine pathway for Chlamydia to reach the large intestine lumen. Thus, genital/hematogenous Chlamydia may reach the large intestine lumen via multiple redundant pathways.

Keywords: Chlamydia; GI tract; liver to intestine; spleen to stomach; spreading pathways.

FIG 1

Effect of spleen removal on the spreading of genital Chlamydia to the gastrointestinal tract. Groups of female C57BL/6J mice without (a and b; n = 5) or with (c and d; n = 6) splenectomy were infected intravaginally with Chlamydia. All mice were monitored for live chlamydial organisms recovered from both vaginal (a and c) and rectal (b and d) swabs, and the titers were expressed as log₁₀ IFU per swab on different days after intravaginal infection. Note that spleen removal failed to significantly impact either live chlamydial shedding from the genital tract or the spread of genital Chlamydia to the gastrointestinal tract. P > 0.05 (a versus c or b versus d, area under the curve, Wilcoxon rank sum). The number of mice with shedding is indicated for the points where not all mice were positive for shedding. The data were acquired from two independent experiments.

FIG 2

Effect of spleen removal on the spreading of hematogenous Chlamydia to the gastrointestinal tract. Groups of female C57BL/6J mice without (a and b; n = 5) or with (c and d; n = 4) splenectomy were inoculated retro-orbitally with Chlamydia. All mice were monitored for live chlamydial organism shedding from both vaginal (a and c) and rectal (b and d) swabs, and the titers were expressed as log₁₀ IFU per swab on different days after intravaginal infection. Note that hematogenous Chlamydia was detected on the rectal swabs but not vaginal swabs of all mice regardless of splenectomy. P > 0.05 (b versus d, area under the curve, Wilcoxon rank sum). The number of mice with shedding is indicated for the points where not all mice were positive for shedding. The data were acquired from two independent experiments.

FIG 3

Temporal distribution of live chlamydial organisms in mouse tissues following intravenous inoculation. After retro-orbital inoculation with Chlamydia, groups of C57BL/6J mice were sacrificed at 12 h (a), 24 h (b), 36 h (c), 48 h (d), or 72 h (e) to monitor live chlamydial organisms in different tissues (solid bars) and luminal contents (open bars), including spleen (Spl), liver (Liv), lung (Lun), kidney (Kid), and gastrointestinal tract tissues and luminal contents from the stomach (Sto), small intestine (SI) (including the duodenum [Duo], jejunum [Jej], and ileum [Ile]), and large intestine (LI) (including the cecum [Cec], colon [Col], and rectum [Rec]), as well as upper genital (UP) and lower genital (LG) tract tissues and vaginal swabs (Vag). The rectum lumen was collected as rectal swabs. The infectious titers of chlamydial organisms were expressed as log₁₀ IFU per tissue/lumen/swab. Note that hematogenous Chlamydia was detected predominantly in the spleen by 12 h, the stomach tissue and lumen (b, arrow) by 24 h, and intestinal tissues by 36 h and intestinal lumen by 48 h (d, arrows). By 72 h, live Chlamydia was first detected on the rectal swabs (e, thick arrow) but not vaginal swabs (e, open arrow). *, P < 0.05, Wilcoxon rank sum (spleen versus liver, lung, or kidney). n = 4 or 5 mice for each time point. Data are from 3 separate experiments. Due to large number of samples to be measured from each mouse, only one or two mice were processed each time. The number of mice with detectable IFU in a given tissue/sample is indicated for the samples that were important for drawing conclusions.

FIG 4

Distribution of intravenously inoculated Chlamydia in tissues of mice housed under coprophagy-free condition. After retro-orbital inoculation with Chlamydia, C57BL/6J mice (n = 5) were sacrificed at 36 h for monitoring for live Chlamydia recovery from different tissues (solid bar) and luminal contents (open bar). Abbreviations for tissues and luminal contents are as in Fig. 3, with the addition of esophagus (Eso) tissue and luminal contents (open arrow). The titers of live chlamydial organisms were expressed as log₁₀ IFU per tissue/lumen/swab. Note that hematogenous Chlamydia was detected predominantly in the spleen and in the stomach lumen (filled arrow) but no other mucosal lumens (open arrow). *, P < 0.05, Wilcoxon rank sum (spleen versus liver, lung, or kidney). n = 5. Data are from 2 separate experiments. The number of mice with detectable IFU in a given tissue/sample is indicated for the samples that were important for drawing conclusions.

FIG 5

Temporal distribution of intravenously inoculated Chlamydia in tissues of splenectomized mice. After retro-orbital inoculation with Chlamydia, groups of splenectomized C57BL/6J mice were sacrificed at 24 h (a), 72 h (b), 7 days (c), or 14 days (d) to monitor live chlamydial organisms in different tissues (solid bars) and luminal contents (open bars). The designations for the tissues and luminal contents are as in Fig. 3. The titers of live chlamydial organisms were expressed as log₁₀ IFU per tissue/lumen/swab. Note that hematogenous Chlamydia was detected predominantly in the liver by 24 h (a) and different lumens of the gastrointestinal tract (b, arrows) by 72 h but not vaginal swabs even by day 14 (d, arrow). *, P < 0.05, Wilcoxon rank sum (liver versus lung or kidney in panel a or intestinal tissues versus stomach tissue in panel b). n = 4 or 5 mice for each time point. Data are from 3 separate experiments. The number of mice with detectable IFU in a given tissue/sample is indicated for the samples that were important for drawing conclusions.