Neuritis and gastrointestinal hemorrhage in scrub typhus patients

Lack of the IFN-γ signal leads to lethal Orientia tsutsugamushi infection in mice with skin eschar lesions

Scrub typhus is an acute febrile disease due to Orientia tsutsugamushi (Ot) infection and can be life-threatening with organ failure, hemorrhage, and fatality. Yet, little is known as to how the host reacts to Ot bacteria at early stages of infection; no reports have addressed the functional roles of type I versus type II interferon (IFN) responses in scrub typhus. In this study, we used comprehensive intradermal (i.d.) inoculation models and two clinically predominant Ot strains (Karp and Gilliam) to uncover early immune events. Karp infection induced sequential expression of Ifnb and Ifng in inflamed skin and draining lymph nodes at days 1 and 3 post-infection. Using double Ifnar1-/-Ifngr1-/- and Stat1-/- mice, we found that deficiency in IFN/STAT1 signaling resulted in lethal infection with profound pathology and skin eschar lesions, which resembled to human scrub typhus. Further analyses demonstrated that deficiency in IFN-γ, but not IFN-I, resulted in impaired NK cell and macrophage activation and uncontrolled bacterial growth and dissemination, leading to metabolic dysregulation, excessive inflammatory cell infiltration, and exacerbated tissue damage. NK cells were found to be the major cellular source of innate IFN-γ, contributing to the initial Ot control in the draining lymph nodes. In vitro studies with dendritic cell cultures revealed a superior antibacterial effect offered by IFN-γ than IFN-β. Comparative in vivo studies with Karp- and Gilliam-infection revealed a crucial role of IFN-γ signaling in protection against progression of eschar lesions and Ot infection lethality. Additionally, our i.d. mouse models of lethal infection with eschar lesions are promising tools for immunological study and vaccine development for scrub typhus.

Endoscopic characteristics of infection-associated peptic ulcers

BACKGROUND

Aside from Helicobacter pylori, another cause for the development or worsening of gastrointestinal ulcers is scrub typhus, an acute febrile disease caused by Orientia tsutsugamushi. We aimed to compare the endoscopic characteristics of peptic ulcers caused by these infectious agents.

METHODS

This retrospective case-control study involved patients who underwent upper gastrointestinal endoscopy at Chosun University Hospital in Korea. We compared endoscopic features and demographic characteristics between patients with H. pylori infection and those with O. tsutsugamushi infection.

RESULTS

A total of 141 patients with peptic ulcer were included in the study. Compared to patients with O. tsutsugamushi infection (n = 62; age, 63.8 ± 12.1 years; male sex, 42%), those with H. pylori infection (n = 79; age, 53.0 ± 14.8 years; male sex, 81%) were younger and more likely to be male (P < .001 for both). Patients with O. tsutsugamushi infection were more likely to have multiple lesions (40/62, 64.5% vs 37/79, 46.8%; P = .042) and irregular-shaped lesions (27/62, 43.6% vs 20/79, 25.3%; P = .031). Patients with H. pylori infection had higher incidence of hemorrhagic ulcers (26/79, 32.9% vs 8/62, 12.9%; P = .007), and lesions occurred most often in the duodenum (43.0%), followed by the antrum (36.7%), body (34.2%), and angle (12.7%) of the stomach. In patients with O. tsutsugamushi infection, lesions occurred most often in the antrum (70.97%), followed by the duodenum (35.5%), body (22.6%), and angle (14.5%) of the stomach. In both groups, gastric ulcer lesions occurred most often in the antrum, followed by the body and angle of the stomach (36.7% vs 70.97%, 34.2% vs 22.6%, and 12.7% vs 14.5% for gastric ulcers associated with H. pylori and O. tsutsugamushi infection, respectively). Patients with O. tsutsugamushi infection had significantly higher incidence of ulcers on the antrum (70.97% vs 36.7%, P < .001) and the greater curvature (45.2% vs 24.0%, P = .012). Finally, 35.5% of patients with gastric ulcer caused by scrub typhus also had duodenal ulcer.

CONCLUSION

This is the first study to compare endoscopic features of peptic ulcers caused by H. pylori and O. tsutsugamushi. Peptic ulcers in patients with H. pylori infection occurred predominantly in the antrum/body/lesser curvature and presented with single, round/oval lesions, while ulcers in patients with scrub typhus occurred predominantly in the antrum/greater curvature and presented with multiple, irregular lesions. Scrub typhus should be considered as a cause of duodenal ulcer in scrub typhus-endemic areas.