Rickettsia typhi infection in severe fever with thrombocytopenia patients, China

Hospital-Based Surveillance of Rickettsial Diseases in Kashmir, North India

Background: Rickettsial diseases were reported from Kashmir, India, in the early 20th century. Since then, limited research was carried that has resulted in a significant gap in understanding these diseases. This study was conducted to find out the prevalence and diversity of rickettsial diseases in this region. Methods: Blood sample from 476 patients were collected. Enzyme-linked immunosorbent assay was done for the detection of IgM and IgG, and immunofluorescence assay was done for endpoint titer determination. Nested polymerase chain reaction was performed for detection of spotted fever group (gltA, sca0, sca5 genes), typhus group (17 kDa gene) scrub typhus group (47 and 56 kDa gene), followed by sequencing and phylogenetic analysis. Results: The seropositivity of scrub typhus, spotted fever group, typhus group was 74 (15.54%), 71 (14.91%), and 60 (12.60%), respectively. Scrub typhus was significantly associated with the urban population (odds ratio = 1.812, 95% confidence interval 1.099-3.0, p = 0.02). Bimodal seasonal variation was observed in all the three groups. In spotted fever group, out of 48 samples 81.25%, 45.83%, and 38.09% were positive for gltA, sca0, and sca5 genes, respectively, and in typhus group 20.83% were positive for 17 kDa. In the scrub typhus group, out of 62 samples, the 56 kDa gene was positive in 56.45%, while the 47 kDa gene was positive in 35.48%. Phylogenetic analysis revealed Rickettsia conorii, Rickettsia parkeri, Rickettsia typhi, and Orientia tsutsugamushi. Conclusions: This study confirms the presence of human rickettsial infections in Kashmir, highlighting the need for including rickettsial diseases in diagnostic algorithm for acute febrile illness.

ATG9 inhibits Rickettsia binding to the host cell surface by blocking the rOmpB-XRCC6/KU70 interaction

ickettsiae are tick-borne pathogens that infect human hosts through poorly characterized mechanisms. Herein, we report that ATG9 (autophagy related 9) plays a previously unrecognized role in inhibiting Rickettsia binding to the host cell surface. Unexpectedly, this new function of ATG9 is likely independent of macroautophagy/autophagy. Instead, ATG9 acts as a host defending factor by binding to XRCC6/KU70, a receptor of the Rickettsia outer-membrane protein rOmpB. Both ATG9 and rOmpB bind to the DNA-binding domain of XRCC6, suggesting a competitive role for ATG9 occupying the binding site of rOmpB to abrogate Rickettsia binding. Furthermore, we show that rapamycin transcriptionally activates ATG9 and inhibits rOmpB-mediated infection in a mouse model. Collectively, our study reveals a novel innate mechanism regulating Rickettsia infection and suggests that agonists of ATG9 May be useful for developing therapeutic strategies for the intervention of rickettsial diseases.Abbreviation: APEX2: apurinic/apyrimidinic endodeoxyribonuclease 2; ATG: autophagy related; BafA1: bafilomycin A1; CQ: chloroquine; E. coli: Escherichia coli; GST: glutathione S-transferase; ICM: immunofluorescence confocal microscopy; IP-Mass: immunoprecipitation-mass spectrometry; KD: knockdown; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MTOR: mechanistic target of rapamycin kinase; rOmpB: rickettsial outer membrane protein B; SAP: SAF-A/B, Acinus, and PIAS; SQSTM1/p62: sequestosome 1; TEM: transmission electron microscopy; TFEB: transcription factor EB; VWA: von Willebrand factor A; XRCC6/KU70: X-ray repair cross complementing 6.

Comparison of Brucellosis and Rickettsiosis in Children: A Retrospective Cohort Study

Background: Fever of Unknown Origin (FUO) is a diagnostic challenge in pediatrics, often stemming from zoonotic infections. In southern Israel, brucellosis and rickettsiosis are endemic and share overlapping clinical features, making diagnosis difficult. We compared the demographic, clinical, and laboratory characteristics of pediatric brucellosis and rickettsiosis to aid in distinguishing between these diseases and guide early empirical treatment. Methods: We performed a retrospective cohort study, conducted between 2005 and 2020, on children who tested positive for either rickettsia or brucella. Data on demographic, clinical, laboratory, treatment, and outcome parameters were analyzed using descriptive, univariate, and multivariate statistical methods. Results: Overall, 775 patients were included, 440 with brucellosis and 335 with rickettsiosis. The majority of patients were of Bedouin ethnicity (99.5% and 90.7%, respectively). In univariate analysis, brucellosis was associated with male gender, young age, limping, anemia, and prolonged hospitalization duration. Rickettsiosis was characterized by high-grade fever, rash, headache, thrombocytopenia, elevated C-reactive protein (CRP), and gastrointestinal, respiratory, and neurological symptoms. Mortality rates were low in both groups (≤0.5%). In multivariate analysis, brucellosis was associated with limping (odds ratio = 7.27; with 95% confidence interval of 5.15-10.38), hemoglobin <10 mg/dL (2.01; 1.14-3.64), age <5 years (1.95; 1.25-3.07), warm season (1.84; 1.31-2.59), and male gender (1.57; 1.10-2.25). Rickettsiosis was associated with a rash (9.06; 3.91-24.9), CRP ≥5 mg/dL (4.03; 1.86-9.81), headache (3.01; 1.75-5.30), thrombocytopenia (2.61; 1.23-6.06), leukopenia (1.88; 1.19-2.98), and temperature ≥39.0 °C (1.66; 1.03-2.68). Conclusions: Brucellosis and rickettsiosis differ demographically and clinically in FUO cases. These findings highlight the importance of distinguishing between the two diseases for early diagnosis and targeted management, ultimately improving patient outcomes.

Co-circulation of Hantavirus, Pathogenic Leptospira spp., and Bartonella spp. in Rodents in the Wanzhou Section of the Three Gorges Reservoir Region, 2021-2023

Background: Rodent is a reservoir of various zoonotic pathogens. Wanzhou section of the Three Gorges reservoir region (TGRR) is a superior habitat for rodents, and the situation of rodent-borne zoonotic pathogens in this region has not been surveyed in recent years. Materials and Methods: Rodents were night trapped with mousecage or mousetrap in urban and surrounding towns' indoor or outdoor areas of the Wanzhou section of the TGRR, and nucleic acid was extracted from their lung or a mixture of liver, spleen, and kidney. Commercialized qPCR kits for pathogenic Leptospira spp., Rickettsia typhi, Anaplasma phagocytophilum, Bartonella spp., Orientia tsutsugamushi, and Francisella tularensis and qRT-PCR kits for hantavirus (HV), and severe fever with thrombocytopenia syndrome virus (SFTSV) were used for the detection of associated pathogens in collected rodents. Results: From 2021 to 2023, 604 rodents belonging to 10 species were collected. HV and pathogenic L. spp. were detected positive, with infection rates of 0.66% (4/604) and 1.32% (8/604), respectively. B. spp. were detected positive with an infection rate of 4.73% (19/402) in the rodents trapped in 2022 and 2023. Other five pathogens were all detected negative. Conclusion: This study showed that the Wanzhou section of the TGRR had HV, pathogenic L. spp., and B. spp. co-circulation in rodents. Hence, more attention should be paid to the prevention and control of associated rodent-borne diseases.

Genetic typing of isolates of Rickettsia typhi

Murine typhus, which is caused by Rickettsia typhi, has a wide range of clinical manifestations. It has a low mortality rate but may result in meningoencephalitis and interstitial pneumonia in severe cases. Comparisons of complete genome sequences of R. typhi isolates from North Carolina, USA (Wilmington), Myanmar (B9991PP), and Thailand (TH1527) identified only 26 single nucleotide polymorphism (SNP) and 7 insertion-deletion (INDEL) sites in these highly syntenic genomes. Assays were developed to further define the distribution of these variant sites among 15 additional isolates of R. typhi with different histories from Asia, the USA, and Africa. Mismatch amplification mutation assays (MAMA) were validated for 22 SNP sites, while the 7 INDEL sites were analyzed directly on agarose gels. Six SNP types, 9 INDEL types, 11 total types were identified among these 18 isolates. Replicate DNA samples as well as comparisons of isolates with different passage and source histories gave consistent genetic typing profiles. Comparison of the SNP and INDEL markers to R. typhi’s nearest neighbor Rickettsia prowazekii demonstrated that the majority of the SNPs represent intra-species variation that arose post divergence of these two species while several INDEL sites also exhibited intraspecies variability among the R. prowazekii genomes that have been completely sequenced. The assays for the presence of these SNP and INDEL sites, particularly the latter, comprise a low technology gel method for consistently distinguishing R. typhi and R. prowazekii as well as for differentiating genetic types of R. typhi.

Rickettsia typhi is an obligately intracellular bacterium which is most commonly transmitted by rat fleas to humans and can cause the disease murine (endemic) typhus wherever both humans and infected rats are present. However, this agent is also present in a variety of other arthropod species associated with other vertebrate animals. Its closest relative is Rickettsia prowazekii, the etiologic agent of epidemic typhus (human louse-borne) and sylvatic typhus (associated with flying squirrels and its ectoparasites in the Eastern United States). Both classic louse-borne and flea-borne typhus rickettsiae can cause fatal infections and have the potential for use as biothreat agents as they can be grown in large quantities. We investigated the genetic differences that can be found in different stocks of R. typhi. Our work is important for two reasons. We have developed robust and sensitive methods for distinguishing isolates of R. typhi originating from different continents; these new assays require only simple instrumentation which is available in nearly all biology laboratories. Our results also provided new insights confirming the probable origin of R. typhi in Asia and its likely cosmopolitan spread by rats on ships around the world.

Clinical features of severe fever with thrombocytopenia syndrome and analysis of risk factors for mortality

Background

To understand the clinical characteristics of and explore the risk factors for mortality in patients with severe fever with thrombocytopenia syndrome (SFTS).

Methods

Data from SFTS patients diagnosed by laboratory examination at Chaohu Hospital affiliated with Anhui Medical University from June 2017 to January 2021 were retrospectively analysed. According to the clinical results, all confirmed patients were divided into the surviving group (80 patients) and non-surviving group (20 patients). The two groups were compared in terms of general characteristics, clinical symptoms and signs, laboratory indicators and other aspects. The independent risk factors for mortality in SFTS patients were analysed by multivariate binary logistic regression.

Results

Univariate analysis showed a significant difference in age and the incidence of consciousness disturbance, respiratory failure, haemorrhagic manifestations, renal dysfunction, shock, aspartate aminotransferase (AST) ≥400 U/L, creatine kinase (CK)≥1000 U/L, creatine kinase isoenzymes (CK-MB) ≥100 U/L, lactate dehydrogenase (LDH) ≥1000 U/L, serum creatinine ≥100 mmol/L, blood urea nitrogen ≥7.5 mmol/L and C-reactive protein ≥8 mg/L between the two groups (P < 0.05).

Conclusions

Consciousness disorder, haemorrhagic manifestations, renal dysfunction, AST ≥ 400 U/L, and LDH ≥ 1000 U/L are independent risk factors for mortality in SFTS patients and merit close attention in clinical treatment to avoid fatal consequences.

Clinical Progress and Risk Factors for Death from Severe Fever with Thrombocytopenia Syndrome: A Multihospital Retrospective Investigation in Anhui, China

Knowledge of the clinical progress of severe fever with thrombocytopenia syndrome (SFTS) and the associated predictors of mortality is important for providing appropriate treatment in severe cases. A multihospital retrospective study was conducted in three SFTS-endemic cities, in 2018. Of the 208 SFTS-confirmed cases, there were 189 survivors and 19 deaths. The median age was 64 years; 104 (50.0%) patients were men, and 188 (90.4%) were farmers. Furthermore, 203 (97.6%) patients reported fever and 70 (33.7%) reported fatigue. Most fatal cases had complications including multiple-organ failure, central nervous syndrome (CNS) abnormalities, and disseminated intravascular coagulation. During the fever phase, alanine transaminase, aspartate aminotransferase (AST), blood urea nitrogen (BUN), creatinine, D-dimer, glucose, hydroxybutyrate dehydrogenase, lactate dehydrogenase (LDH), procalcitonin, prothrombin time, and uric acid levels were higher in fatal than in nonfatal cases (P < 0.05). Creatine kinase (CK), CK-MB (CKMB), AST, and LDH levels were significantly lower in nonfatal than in fatal cases (P < 0.05). Central nervous syndrome abnormalities (odds ratio [OR] = 20.9, 95% CI: 4.3, 100), body temperature ≥ 38.5°C (OR = 23.2, 95% CI: 3.4, 158), BUN levels ≥ 6.4 mmol/L (OR = 9.9, 95% CI: 2.2, 44), CKMB levels ≥ 100 U/L (OR = 33.2, 95% CI: 5.8, 192), and LDH levels ≥ 1,000 U/L (OR = 8.3, 95% CI: 1.9, 37) were predictors of mortality. Our findings reveal that the presence of specific complications and laboratory parameters may serve as predictors of mortality and aid in early identification of severe SFTS cases in clinical practice.