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MMWR. Morbidity and Mortality Weekly... Aug 2023Fleaborne typhus (also known as murine typhus), a widely distributed vectorborne zoonosis caused by Rickettsia typhi, is a moderately severe, but infrequently fatal...
Fleaborne typhus (also known as murine typhus), a widely distributed vectorborne zoonosis caused by Rickettsia typhi, is a moderately severe, but infrequently fatal illness; among patients who receive doxycycline, the case-fatality rate is <1%. Fleaborne typhus is a mandated reportable condition in California. Reported fleaborne typhus cases in Los Angeles County have been increasing since 2010, with the highest number (171) reported during 2022. During June-October 2022, Los Angeles County Department of Public Health learned of three fleaborne typhus-associated deaths. This report describes the clinical presentation, illness course, and methods used to diagnose fleaborne typhus in these three cases. Severe fleaborne typhus manifestations among these cases included hemophagocytic lymphohistiocytosis, a rare immune hyperactivation syndrome that can occur in the infection setting; myocarditis; and septic shock with disseminated intravascular coagulation. Increased health care provider and public health awareness of the prevalence and severity of fleaborne typhus and of the importance of early doxycycline therapy is essential for prevention and treatment efforts.
Topics: Mice; Humans; Doxycycline; Typhus, Epidemic Louse-Borne; Los Angeles; Typhus, Endemic Flea-Borne; Rickettsia typhi; Animals
PubMed: 37535465
DOI: 10.15585/mmwr.mm7231a1 -
Clinical Microbiology and Infection :... Dec 2009
Topics: Animals; Antibodies, Bacterial; Dog Diseases; Dogs; Female; Fluorescent Antibody Technique, Indirect; Immunoglobulin G; Male; Rickettsia Infections; Rickettsia felis; Rickettsia typhi; Seroepidemiologic Studies; Spain
PubMed: 19392898
DOI: 10.1111/j.1469-0691.2008.02156.x -
Research in Microbiology 1992Human vascular endothelial, Vero and human embryonic lung cells infected with rickettsiae for 24 h or 48 h were labelled for polymerized actin with NBD-phallacidin....
Human vascular endothelial, Vero and human embryonic lung cells infected with rickettsiae for 24 h or 48 h were labelled for polymerized actin with NBD-phallacidin. Between 20 and 68% of the intracellular Rickettsia conorii had an actin tail of between 0.33 and 15 microns, with the longest tails being observed in Vero cells. In the case of R. typhi less than 1% of the organisms had actin tails and these were considerably shorter than those of R. conorii. These findings provide new information concerning the different cytopathic effects observed with the two rickettsial species.
Topics: Actins; Cell Movement; Endothelium, Vascular; Humans; In Vitro Techniques; Microscopy, Fluorescence; Polymers; Rickettsia; Rickettsia Infections; Rickettsia typhi; Virulence
PubMed: 1299836
DOI: 10.1016/0923-2508(92)90069-z -
The American Journal of Tropical... Sep 2014Rickettsial infections represent a major cause of non-malarial febrile illnesses among the residents of Southeast Asia and returned travelers from that region. There are... (Review)
Review
Rickettsial infections represent a major cause of non-malarial febrile illnesses among the residents of Southeast Asia and returned travelers from that region. There are several challenges in recognition, diagnosis, and management of rickettsioses endemic to Southeast Asia. This review focuses on the prevalent rickettsial infections, namely, murine typhus (Rickettsia typhi), scrub typhus (Orientia tsutsugamushi), and members of spotted fever group rickettsiae. Information on epidemiology and regional variance in the prevalence of rickettsial infections is analyzed. Clinical characteristics of main groups of rickettsioses, unusual presentations, and common pitfalls in diagnosis are further discussed. In particular, relevant epidemiologic and clinical aspects on emerging spotted fever group rickettsiae in the region, such as Rickettsia honei, R. felis, R. japonica, and R. helvetica, are presented. Furthermore, challenges in laboratory diagnosis and management aspects of rickettsial infections unique to Southeast Asia are discussed, and data on emerging resistance to antimicrobial drugs and treatment/prevention options are also reviewed.
Topics: Animals; Anti-Infective Agents; Antibodies, Bacterial; Asia, Southeastern; Drug Resistance, Bacterial; Fever; Humans; Orientia tsutsugamushi; Prevalence; Rickettsia; Rickettsia Infections; Rickettsia typhi; Scrub Typhus; Travel
PubMed: 24957537
DOI: 10.4269/ajtmh.14-0191 -
Biomedica : Revista Del Instituto... Oct 2021Introduction: Rickettsioses are zoonotic diseases transmitted by arthropods acting as vectors and reservoirs. Disease symptoms are nonspecific and, therefore, their...
Introduction: Rickettsioses are zoonotic diseases transmitted by arthropods acting as vectors and reservoirs. Disease symptoms are nonspecific and, therefore, their clinical diagnosis is difficult. Indirect immunofluorescence (IFA) is the gold standard assay for diagnosis. The interest for conducting studies on these pathologies has resurfaced in Colombia since 2001; besides, previous studies have evidenced cases of rickettsiosis in the north of the department of Caldas. Objective: To establish the frequency of antibodies and seroconversion against Rickettsia spp. In patients consulting health institutions in Caldas, Colombia, from 2016 to 2019. Materials and methods: We conducted a quantitative, observational, and descriptive study on a non-probabilistic sample of 175 patients with symptoms compatible with rickettsiosis who consulted in different municipalities of Caldas, Colombia; IFA was performed to detect antibodies in the acute and convalescent phases against Rickettsia rickettsii, Rickettsia typhi, and Rickettsia felis. Results: The average age of the patients was 31 years. The municipalities with the highest proportion of seropositive cases were Belalcázar, Chinchiná, Filadelfia, La Dorada, La Merced, and Manizales; 66% of patients owned pets and 12% reported arthropod bites. The most frequent signs and symptoms were headache (69.7%), arthromyalgia (60%), and fever (58.2%). IgG seroprevalence was 60% for R. rickettsii, 47.9% for R. typhi, and, and 24% for R. felis. Eight patients presented seroconversion. Conclusion: We found evidence of the circulation of Rickettsia species from the spotted fever group and the typhus group associated with human cases in Caldas.
Topics: Adult; Antibodies, Bacterial; Colombia; Humans; Rickettsia; Rickettsia Infections; Seroconversion; Seroepidemiologic Studies
PubMed: 34669282
DOI: 10.7705/biomedica.5712 -
BMC Genomics Dec 2015Rickettsia species are obligate intracellular Gram-negative pathogenic bacteria and the etiologic agents of diseases such as Rocky Mountain spotted fever (RMSF),...
BACKGROUND
Rickettsia species are obligate intracellular Gram-negative pathogenic bacteria and the etiologic agents of diseases such as Rocky Mountain spotted fever (RMSF), Mediterranean spotted fever, epidemic typhus, and murine typhus. Genome sequencing revealed that R. prowazekii has ~25 % non-coding DNA, the majority of which is thought to be either "junk DNA" or pseudogenes resulting from genomic reduction. These characteristics also define other Rickettsia genomes. Bacterial small RNAs, whose biogenesis is predominantly attributed to either the intergenic regions (trans-acting) or to the antisense strand of an open reading frame (cis-acting), are now appreciated to be among the most important post-transcriptional regulators of bacterial virulence and growth. We hypothesize that intergenic regions in rickettsial species encode for small, non-coding RNAs (sRNAs) involved in the regulation of its transcriptome, leading to altered virulence and adaptation depending on the host niche.
RESULTS
We employed a combination of bioinformatics and in vitro approaches to explore the presence of sRNAs in a number of species within Genus Rickettsia. Using the sRNA Identification Protocol using High-throughput Technology (SIPHT) web interface, we predicted over 1,700 small RNAs present in the intergenic regions of 16 different strains representing 13 rickettsial species. We further characterized novel sRNAs from typhus (R. prowazekii and R. typhi) and spotted fever (R. rickettsii and R. conorii) groups for their promoters and Rho-independent terminators using Bacterial Promoter Prediction Program (BPROM) and TransTermHP prediction algorithms, respectively. Strong σ70 promoters were predicted upstream of all novel small RNAs, indicating the potential for transcriptional activity. Next, we infected human microvascular endothelial cells (HMECs) with R. prowazekii for 3 h and 24 h and performed Next Generation Sequencing to experimentally validate the expression of 26 sRNA candidates predicted in R. prowazekii. Reverse transcriptase PCR was also used to further verify the expression of six putative novel sRNA candidates in R. prowazekii.
CONCLUSIONS
Our results yield clear evidence for the expression of novel R. prowazekii sRNA candidates during infection of HMECs. This is the first description of novel small RNAs for a highly pathogenic species of Rickettsia, which should lead to new insights into rickettsial virulence and adaptation mechanisms.
Topics: Base Sequence; Chromosome Mapping; Computational Biology; Consensus Sequence; Gene Expression Regulation, Bacterial; Genome, Bacterial; Genomics; High-Throughput Nucleotide Sequencing; Molecular Sequence Data; Nucleotide Motifs; Position-Specific Scoring Matrices; Promoter Regions, Genetic; RNA Interference; RNA, Bacterial; RNA, Small Untranslated; Reproducibility of Results; Rickettsia
PubMed: 26679185
DOI: 10.1186/s12864-015-2293-7 -
The American Journal of Tropical... Apr 2022Scrub typhus group (STG), typhus group (TG), and spotted fever group (SFG) rickettsiae are pathogens distributed worldwide and are important causes of febrile illnesses...
Scrub typhus group (STG), typhus group (TG), and spotted fever group (SFG) rickettsiae are pathogens distributed worldwide and are important causes of febrile illnesses in southeast Asia. The levels of rickettsioses burden and distribution in Thai communities are still unclear. Nonspecific symptoms, limit diagnostic capacity and underdiagnoses contribute to the absence of clarity. The objective of this study was to determine the nationwide IgG seroprevalence of STG, TG, and SFG by ELISA in repository sera from the Royal Thai Army recruits collected during 2007-2008 and 2012 to estimate rickettsiae exposure in young Thai men to better understand rickettsiae exposure distribution in the Thai population. IgG seroprevalence of STG, Orientia tsutsugamushi; TG, Rickettsia typhi; and SFG, R. rickettsii was 12.4%, 6.8%, and 3.3% in 2007-2008 and 31.8%, 4.2%, and 4.5% in 2012, respectively. The STG had the highest seroprevalence of Rickettsia assessed, with the highest regional seroprevalence found in southern Thailand. The STG seroprevalence changed significantly from 2007 to 2008 (P value < 0.05), which corresponds with morbidity rate of scrub typhus from the last decade in Thailand. We were unable to determine the causality for seroprevalence changes between the two periods due to the limitation in sample numbers for intervening years and limited information available for archived specimens. Additional research would be required to determine agency. However, study results do confirm Rickettsia endemicity in Thailand lends weight to reports of increasing STG seroprevalence. It also corroborates the need to raise rickettsial disease awareness and educate the general public in prevention measures.
PubMed: 35378507
DOI: 10.4269/ajtmh.20-1512 -
Journal of Bacteriology Sep 2012Rickettsia typhi, the causative agent of murine (endemic) typhus, is an obligate intracellular pathogen with a life cycle involving both vertebrate and invertebrate...
Rickettsia typhi, the causative agent of murine (endemic) typhus, is an obligate intracellular pathogen with a life cycle involving both vertebrate and invertebrate hosts. In this study, we characterized a gene (RT0218) encoding a C-terminal ankyrin repeat domain-containing protein, named Rickettsia ankyrin repeat protein 1 (RARP-1), and identified it as a secreted effector protein of R. typhi. RT0218 showed differential transcript abundance at various phases of R. typhi intracellular growth. RARP-1 was secreted by R. typhi into the host cytoplasm during in vitro infection of mammalian cells. Transcriptional analysis revealed that RT0218 was cotranscribed with adjacent genes RT0217 (hypothetical protein) and RT0216 (TolC) as a single polycistronic mRNA. Given one of its functions as a facilitator of extracellular protein secretion in some Gram-negative bacterial pathogens, we tested the possible role of TolC in the secretion of RARP-1. Using Escherichia coli C600 and an isogenic tolC insertion mutant as surrogate hosts, our data demonstrate that RARP-1 is secreted in a TolC-dependent manner. Deletion of either the N-terminal signal peptide or the C-terminal ankyrin repeats abolished RARP-1 secretion by wild-type E. coli. Importantly, expression of R. typhi tolC in the E. coli tolC mutant restored the secretion of RARP-1, suggesting that TolC has a role in RARP-1 translocation across the outer membrane. This work implies that the TolC component of the putative type 1 secretion system of R. typhi is involved in the secretion process of RARP-1.
Topics: Animals; Ankyrin Repeat; Bacterial Outer Membrane Proteins; Bacterial Proteins; Cell Line; Escherichia coli; Escherichia coli Proteins; Gene Deletion; Gene Expression Profiling; Genetic Complementation Test; Humans; Membrane Transport Proteins; Mutagenesis, Insertional; Rickettsia typhi; Transcription, Genetic
PubMed: 22773786
DOI: 10.1128/JB.00793-12 -
Memorias Do Instituto Oswaldo Cruz Dec 2005Rickettsial diseases except those belonging to spotted fever group rickettsioses are poorly studied in South America particularly in Brazil where few epidemiological...
Antibodies to Rickettsia rickettsii, Rickettsia typhi, Coxiella burnetii, Bartonella henselae, Bartonella quintana, and Ehrlichia chaffeensis among healthy population in Minas Gerais, Brazil.
Rickettsial diseases except those belonging to spotted fever group rickettsioses are poorly studied in South America particularly in Brazil where few epidemiological reports have been published. We describe a serosurvey for Rickettsia rickettsii, R. typhi, Coxiella burnetii, Bartonella henselae, B. quintana, and Ehrlichia chaffeensis in 437 healthy people from a Brazilian rural community. The serum samples were tested by indirected micro-immunoflourescence technique and a cutoff titer of 1:64 was used. The seroprevalence rates for R. rickettsii, R. typhi, C. burnetii, B. henselae, B. quintana, and E. chaffeensis were respectively 1.6% (7 samples); 1.1% (5 samples); 3.9% (17 samples); 13.7% (60 samples); 12.8% (56 samples), and 10.5% (46 samples). Frequent multiple/cross-reactivity was observed in this study. Age over 40 years old, urban profession, and rural residence were significantly associated with some but not all infections rate. Low seropositivity rates for R. rickettsii, R. typhi, and C. burnetii contrasted with higher rates of seropositivity for B. quintana, B. henselae, and E. chaffeensis. These results show that all tested rickettsial species or antigenically closely related possible exist in this particular region.
Topics: Adolescent; Adult; Aged; Aged, 80 and over; Antibodies, Bacterial; Antigens, Bacterial; Bartonella; Brazil; Child; Child, Preschool; Coxiella burnetii; Cross Reactions; Ehrlichia chaffeensis; Female; Fluorescent Antibody Technique, Indirect; Gram-Negative Bacteria; Gram-Negative Bacterial Infections; Humans; Male; Middle Aged; Rickettsia; Rural Population; Seroepidemiologic Studies
PubMed: 16444416
DOI: 10.1590/s0074-02762005000800006 -
Vaccines Jan 2023In recent years, promising vaccination strategies against rickettsiosis have been described in experimental animal models and human cells. OmpB is considered an...
In recent years, promising vaccination strategies against rickettsiosis have been described in experimental animal models and human cells. OmpB is considered an immunodominant antigen that is recognized by T and B cells. The aim of this study was to identify TCD4+INF-γ+ and TCD8+INF-γ+ lymphocytes in an autologous system with macrophages transfected with the vaccine candidate pVAX1-OmpB24. Lymphocytes and monocytes from 14 patients with Rickettsia were isolated from whole blood. Monocytes were differentiated into macrophages and transfected with the plasmid pVAX1-OmpB24 pVax1. Isolated lymphocytes were cultured with transfected macrophages. IFN-γ-producing TCD4+ and TCD8+ lymphocyte subpopulations were identified by flow cytometry, as was the percentage of macrophages expressing CD40+, CD80+, HLA-I and HLA-II. Also, we analyzed the exhausted condition of the T lymphocyte subpopulation by PD1 expression. Macrophages transfected with pVAX1-OmpB24 stimulated TCD4+INF-γ+ cells in healthy subjects and patients infected with . Macrophages stimulated TCD8+INF-γ+ cells in healthy subjects and patients infected with and . Cells from healthy donors stimulated with OmpB-24 showed a higher percentage of TCD4+PD1+. Cells from patients infected with had a higher percentage of TCD8+PD-1+, and for those infected with the larger number of cells corresponded to TCD4+PD1+. Human macrophages transfected with pVAX1-OmpB24 activated TCD4+IFN-γ+ and CD8+IFN-γ+ in patients infected with different Rickettsia species. However, PD1 expression played an important role in the inhibition of T lymphocytes with
PubMed: 36680017
DOI: 10.3390/vaccines11010173