Pathologic study of mice infected with Rickettsia tsutsugamushi R19 strain

Not Only Leptotrombidium spp. an Annotated Checklist of Chigger Mites (Actinotrichida: Trombiculidae) Associated with Bacterial Pathogens

Mites of the family Trombiculidae are known for playing a role in maintaining and spreading the scrub typhus etiologic agent, an intracellular Gram-negative bacterium, Orientia tsutsugamushi. Species of the genus Leptotrombidium are investigated most thoroughly, particularly in SE Asia, and a few are proven vectors for the pathogen. The mentioned association, however, is not the only one among trombiculids. Here, we present a list of chiggers indicated in the literature as positive for bacterial pathogens, tested throughout almost 100 years of research. Taxonomic identities of trombiculids follow recent revisions and checklists. Results point at 100 species, from 28 genera, evidenced for association with 31 bacterial taxa. Pathogen-positive mites constitute around 3.3% of the total number of species comprising the family. Discussed arachnids inhabit six biogeographic realms and represent free-living instars as well as external and internal parasites of rodents, soricomorphs, scadents, lagomorphs, peramelemorphs, bats, passerine birds, reptiles and humans. A variety of so far detected bacteria, including novel species, along with the mites’ vast geographical distribution and parasitism on differentiated hosts, indicate that revealing of more cases of Trombiculidae-pathogens association is highly probable, especially utilizing the newest techniques enabling a large-scale bacterial communities survey.

Clinical significance of abnormal chest radiographic findings for acute kidney injury in patients with scrub typhus

Background

Abnormal chest radiographs are frequently encountered in patients with scrub typhus. This study aimed to investigate whether chest radiography on admission is significant as a predictive factor for acute kidney injury (AKI) in patients with scrub typhus.

Methods

From 2010 to 2016, 467 patients were diagnosed with scrub typhus in our hospital. We divided the patients into two groups: normal chest radiograph (NCR) and abnormal chest radiograph (AbNCR), based on chest radiography findings. The incidence, clinical characteristics, and severity of AKI were compared between AKI and non-AKI groups according to the RIFLE classification.

Results

Of the 467 patients, 96 (20.6%) constituted the AbNCR group. Compared with NCR patients, AbNCR patients were older (71 ± 11 vs. 62 ± 13 years, P < 0.001) and had higher total leukocyte counts (9.43 × 10³/mL vs. 6.98 × 10³/mL, P < 0.001). The AbNCR group had significantly longer duration of hospital stay (8.9 ± 5.5 vs. 6.3 ± 2.8 days, P < 0.001) and higher incidence of AKI (46.9% vs. 15.1%, P < 0.001). The common abnormal chest radiographic findings were pulmonary abnormalities, such as pulmonary congestion and pleural effusion. The overall AKI incidence was 21.6%, of which 12.4%, 7.9%, and 1.3% cases were classified as risk, injury, and failure, respectively. In a multivariable logistic regression analysis for association with AKI, old age, presence of chronic kidney disease or hypertension, leukocytosis, hypoalbuminemia, and chest radiographic abnormalities on admission were significant predictors of AKI.

Conclusion

Chest radiographic abnormalities on admission were independently associated with AKI in patients with scrub typhus.

The clinical characteristics of pleural effusion in scrub typhus

Background

The aim of this study is to identify the factors associated with the occurrence of pleural effusion and to investigate the characteristics of pleural effusion in scrub typhus.

Methods

We conducted a retrospective analysis of the medical records of scrub typhus patients between January 2004 and December 2011 at Chosun University Hospital in South Korea. A total of 445 scrub typhus patients were divided into the following two groups: without (n = 352) or with pleural effusion (n = 93). The data of 18 scrub typhus patients who underwent thoracentesis were summarized.

Results

Multivariate analysis demonstrated that the following factors were associated with the occurrence of pleural effusion in scrub typhus: older age (odds ratio [OR] = 1.029, P = 0.037, confidence interval [CI] = 1.002–1.056); male gender (OR = 1.924, P = 0.020, CI = 1.109–3.340); presence of heart failure (OR = 2.628, P = 0.039, CI = 1.052–6.565); and lower albumin (OR = 0.107, P ≤ 0.001, CI = 0.058–0.196). Most pleural effusion presentations were bilateral (88 %) and small (91 %). The effusion had transudate characteristics in 7 patients and exudate characteristics in 11 patients based on Light’s criteria.

Conclusions

This study provided the first data regarding the following four independent risk factors associated with the occurrence of pleural effusion: older age; male gender; the presence of heart failure; and lower albumin. The pleural effusion presentations in scrub typhus patients were bilateral and small in most cases, with transudate and/or exudate characteristics.

Chest radiographic presentation in patients with scrub typhus

We conducted a retrospective study of the adult patients (age ≥18 years) with serologically confirmed scrub typhus admitted between January 1998 and December 2009 at Kaohsiung Chang Gung Memorial Hospital. There were 63 adult scrub typhus patients with chest radiographic examinations. A total of 147 chest radiographs were obtained and reviewed. The most frequent abnormal findings in this study were parenchymal infiltration with bilateral and lower lung predilection. The distribution of abnormal chest radiographs was observed more than 50% during the first week. Furthermore, the progressive change was frequently observed during the first week. There is a significant correlation among laboratory findings, clinical course, and outcome. Chest radiography may be a complementary tool to evaluate the clinical course of scrub typhus and chest radiographic examinations should be taken during the first week after the onset of illness.

Clinical significance of hypoalbuminemia in outcome of patients with scrub typhus

Background

This study was designed to investigate the clinical significance of hypoalbuminemia as a marker of severity and mortality in patients with Scrub typhus.

Methods

The patients with scrub typhus were divided into two groups based on the serum albumin levels; Group I (serum albumin <3.0 g/dL) and Group II (serum albumin ≥3.0 g/dL). The outcome of patients with hypoalbuminemia was compared with that of normoalbuminemia.

Results

Of the total 246 patients who underwent the study, 84 patients (34.1%) were categorized as Group I and 162 patients were (65.9%) as Group II. Group I showed significantly higher incidence of confusion (24.6% vs. 5.3%, p < 0.001), pulmonary edema (15.8% vs. 3.2%, p = 0.002), pleural effusion (22.8% vs. 11.1%, p = 0.03), arrhythmia (12.3% vs. 2.6%, p = 0.008) and non-oliguric acute renal failure (40.4% vs. 11.1%, p < 0.001) compared to group II. Hypoalbuminemic group had a higher APACHE II score (11.37 ± 5.0 vs. 6.94 ± 4.2, p < 0.001), longer hospital stay (19.9 ± 42.1 days vs 7.5 ± 13.8 days, p = 0.012), and higher hospital cost compared to Group II.

Conclusions

This study showed hypoalbuminemia in scrub typhus was closely related to the frequency of various complication, longer hospital stay, consequently the higher medical cost, necessitating more efficient management of patients, including medical resources.

Pulmonary pathology in patients associated with scrub typhus

AIMS

Scrub typhus is a zoonotic disease caused by Orientia tsutsugamushi. Severe cases resulting in mortality from this disease have rarely been reported. We present two scrub typhus cases (a man and a girl) who died of acute respiratory distress syndrome (ARDS).

METHODS

Autopsies were performed. Histopathological and immunohistochemical stains were employed using specific antibody for O. tsutsugamushi and inducible nitric oxide synthase (iNOS).

RESULTS

These subjects developed respiratory distress shortly after admission, and expired following respiratory failure. At autopsy, generalised lymphadenopathy was observed. The lung weight was about two-fold the normal value. Gross inspection revealed oedematous and haemorrhagic lungs. Microscopic examination revealed diffuse alveolar damage with hyaline membrane formation and interstitial pneumonitis with infiltration of inflammatory cells. Immunohistochemical stain showed O. tsutsugamushi antigen depositions in the endothelial cells. We also demonstrated iNOS in the alveolar macrophages and lung tissue debris in both cases.

CONCLUSION

Scrub typhus is usually a mild infectious disease. Our cases present the most dramatic example of sudden death due to ARDS in a short period of time. The clinical investigation and analysis suggest direct endothelial cell invasion of the organism and marked iNOS expression may be involved in the pathogenesis of ARDS associated with scrub typhus.

Clinical role of interstitial pneumonia in patients with scrub typhus: a possible marker of disease severity

Interstitial pneumonia (IP) frequently occurs in patients with scrub typhus, but its clinical significance is not well known. This study was designed to evaluate interstitial pneumonia as a marker of severity of the disease for patients with scrub typhus. We investigated clinical parameters representing the severity of the disease, and the chest radiographic findings for 101 patients with scrub typhus. We then compared these clinical factors between patients with and without IP. We also studied the relationship between IP and other chest radiographic findings. The chest radiography showed IP (51.4%), pleural effusion (42.6%), cardiomegaly (14.9%), pulmonary alveolar edema (20.8%), hilar lymphadenopathy (13.8%) and focal atelectasis (11.8%), respectively. The patients with IP (n=52) had higher incidences in episode of hypoxia (p=0.030), hypotension (p=0.024), severe thrombocytopenia (p=0.036) and hypoalbuminemia (p=0.013) than the patients without IP (n=49). The patients with IP also had higher incidences of pleural effusion (p<0.001), focal atelectasis (p=0.019), cardiomegaly (p<0.001), pulmonary alveolar edema (p=0.011) and hilar lymphadenopathy (p<0.001) than the patients without IP. Our data suggest that IP frequently occurs for patients with scrub typhus and its presence is closely associated with the disease severity of scrub typhus.

Orientia tsutsugamushi suppresses the production of inflammatory cytokines induced by its own heat-stable component in murine macrophages

Orientia tsutsugamushi is a Gram-negative obligate intracellular bacterium, which causes scrub typhus. To understand the pathogenesis of scrub typhus, we have investigated the induction of tumor necrosis alpha (TNF-alpha) and interleukin-6 (IL-6) by O. tsutsugamushi in two murine macrophage cell lines. Both live and heat-killed orientia stimulated the production of cytokines in J774A.1 cells. Polymyxin B does not affect the secretion of cytokines. These together with the fact that the immature macrophage cell line, P388D1, did not produce TNF-alpha when induced by either live or heat-killed O. tsutsugamushi strongly argue against any roles of lipopolysaccharide (LPS) in cytokine production. Furthermore, the result that the cytokine responses were more brisk when macrophage cell lines had been induced by heat-killed O. tsutsugamushi than by live organisms strongly suggest that a heat-stable molecule might be responsible for the induction of cytokine production and O. tsutsugamushi might have mechanisms suppressing the production of inflammatory cytokines induced by its own heat-stable molecule.

Scrub typhus: radiological and clinical findings

OBJECTIVES

To describe the radiological and clinical findings of scrub typhus. We retrospectively analysed the radiographic, thin-section CT and clinical features of scrub typhus.

METHODS

The study included 75 consecutive patients (median age = 47 years, range = 18-81 years) with scrub typhus. Plain chest radiographs were obtained in all 75 patients and 19 underwent thin-section CT within 6 days of initial radiography. The radiographic and thin-section CT findings were retrospectively analysed by three radiologists.

RESULTS

Most common clinical symptoms were fever (73/75, 98%), myalgia (61/75, 81%) and headache (60/75%, 80%). Rash (59/75, 79%) and eschar (56/75, 75%) were the most common signs. Radiography showed abnormalities in 54/75 (72%) patients. The most frequent findings were parenchymal abnormalities (53/75, 71%) with lower lung predilection including bilateral reticulonodular opacities (30/75, 40%), ground-glass opacity (19/75, 25%), consolidation (19/75, 25%), septal lines (27/75, 36%) and hilar lymph node enlargement (19/75, 25%). Thin-section CT (n = 19) showed ground-glass opacity (17/19, 89%) predominantly in the lower zones. Bronchial wall thickening (11/19, 58%), centrilobular nodules (9/19, 47%) and interlobular septal thickening (9/19, 47%) were less frequent findings.

CONCLUSIONS

Scrub typhus is an acute febrile illness characterized by eschar, which usually has a limited course without serious complication. Diffuse bilateral reticulonodular opacities with lower lung predominance was the most frequent radiographic finding. Chest radiography and thin-section CT show pulmonary interstitial disease which may have a component of pulmonary oedema secondary to cardiac dysfunction.

Apoptosis of endothelial cell line ECV304 persistently infected with Orientia tsutsugamushi

Endothelial cells are major targets of Orientia tsutsugamushi. To examine the consequences of the infection of endothelial cells with O. tsutsugamushi, we used human endothelial cell line ECV304. Persistent infection was established and infected cultures could be maintained for over seven months without the addition of normal cells. The heavily infected cells became round and floated in the culture medium, harboring large numbers of organisms inside them. Some of the infected ECV304 cells showed features of apoptotic cells, as determined by the terminal deoxytransferase-mediated dUTP nick end-labeling reaction and DNA fragmentation. We also found that O. tsutsugamushi increased transcription of the mRNAs of proinflammatory cytokines such as IL-6 and IL-8. These results show the first evidence of in vitro-persistent infection by O. tsutsugamushi, which may be related to in vivo persistence reported previously.

Antigenic relationship among the eight prototype and new serotype strains of Orientia tsutsugamushi revealed by monoclonal antibodies

Orientia tsutsugamushi, the etiologic agent of tsutsugamushi disease, exhibits great antigenic variation. Three classical strains (Karp, Gilliam, and Kato) and new antigenic types from Thailand (TA686, TA678, TA716, TA763, and TH1817) have been used as prototype strains of O. tsutsugamushi in many studies. In this study, monoclonal antibodies to the five Thailand strains were produced, and their reactivity against prototype strains and newly identified isolates from Korea and Japan was tested. With a panel of these monoclonal antibodies, we could analyze the antigenic relationship among various strains of O. tsutsugamushi from Thailand, Japan, and Korea. Twelve strains of the O. tsutsugamushi tested showed various reactivities to monoclonal antibodies, and no distinct pattern of reactivity was found according to their location of isolation. Although the Boryong and Kuroki strains were similar in reactivities to most monoclonal antibodies, several monoclonal antibodies could differentiate the two strains. These results indicate that the immunofluorescence antibody test using monoclonal antibodies used in this study is valuable for analyzing the antigenic relationship and classification of O. tsutsugamushi.

Liver involvement in Tsutsugamushi disease

Tsutsugamushi disease, one of the rickettsiosis, is known to be occasionally accompanied by elevation of hepatic enzyme levels. However, there are only a few reports on histopathological findings of the liver. We presented a case of Tsutsugamushi disease with liver involvement. A 51-year-old man suffered from eruptions and a high fever with a mild transaminasemia. He was diagnosed as Tsutsugamushi disease by detection of IgM class antibody against Rickettsia tsutsugamushi. Laparoscopic examination showed a dark-brown liver with diffuse whitish markings. Microscopic findings were consistent with the features of non-specific reactive hepatitis: sinusoidal small lymphocyte infiltrations, mild disarray of hepatocytes and aggregation of T lymphocytes and macrophages in the lobule.