The Typhus-Rocky Mountain Spotted Fever Group: An Epidemiological and Clinical Study in the Eastern and Southeastern States

1931 ◽  
Vol 46 (9) ◽  
pp. 470 ◽  
Author(s):  
A. Rumreich ◽  
R. E. Dyer ◽  
L. F. Badger
Keyword(s):  
Clinical Study ◽  
Spotted Fever ◽  
Rocky Mountain ◽  
Spotted Fever Group ◽  
Rocky Mountain Spotted Fever

Infections due to Rickettsia and Related Organisms

2017 ◽  
Author(s):  
Lucas S Blanton
Keyword(s):  
Q Fever ◽  
Spotted Fever ◽  
Dynamic Change ◽  
Clinical Manifestations ◽  
Rocky Mountain ◽  
Febrile Illness ◽  
American Southwest ◽  
Diagnostic Methods ◽  
Spotted Fever Group ◽  
Rocky Mountain Spotted Fever

Infections caused by organisms of the genus Rickettsia, Orientia, Ehrlichia, Anaplasma, and Coxiella occur throughout the world and are important, yet often overlooked, causes of febrile illness. They are transmitted by ticks, lice, mites, fleas, and, in the case of Coxiella, infected aerosols. Some are considered emerging and reemerging infectious diseases, as exemplified by the emergence of Rocky Mountain spotted fever in the American Southwest and Mexico; the reemergence of murine typhus in parts of Texas; and the discovery of new pathogens, such as Ehrlichia muris–like agent. Manifestations are usually of an acute undifferentiated febrile illness, with associated headache, malaise, myalgias, and varying frequency of rash. Since confirmation of diagnosis is often retrospective, requiring the dynamic change in antibody titers from acute and convalescent phase sera, clinical recognition for empirical treatment is imperative. Indeed, timely treatment is effective at abating symptoms and preventing complications. This review discusses important aspects of the epidemiology, clinical manifestations, diagnostic methods, and treatment of infections caused by Rickettsia and related organisms.  This review contains 5 figures, 9 tables, and 50 references. Key words: anaplasmosis, ehrlichiosis, Q fever, Rocky Mountain spotted fever, scrub typhus, spotted fever group rickettsioses, typhus group rickettsioses

scholarly journals Proteolytic Cleavage of the Immunodominant Outer Membrane Protein rOmpA in Rickettsia rickettsii

2016 ◽  
Vol 199 (6) ◽  
Author(s):  
Nicholas F. Noriea ◽  
Tina R. Clark ◽  
David Mead ◽  
Ted Hackstadt
Keyword(s):  
Outer Membrane ◽  
Cleavage Site ◽  
Spotted Fever ◽  
Protein A ◽  
Rocky Mountain ◽  
Spotted Fever Group ◽  
Rocky Mountain Spotted Fever ◽  
Content Type ◽  
Rickettsia Rickettsii ◽  
Carboxy Terminal

ABSTRACT Rickettsia rickettsii, the causative agent of Rocky Mountain spotted fever, contains two immunodominant proteins, rOmpA and rOmpB, in the outer membrane. Both rOmpA and rOmpB are conserved throughout spotted fever group rickettsiae as members of a family of autotransporter proteins. Previously, it was demonstrated that rOmpB is proteolytically processed, with the cleavage site residing near the autotransporter domain at the carboxy-terminal end of the protein, cleaving the 168-kDa precursor into apparent 120-kDa and 32-kDa fragments. The 120- and 32-kDa fragments remain noncovalently associated on the surface of the bacterium, with implications that the 32-kDa fragment functions as the membrane anchor domain. Here we present evidence for a similar posttranslational processing of rOmpA. rOmpA is expressed as a predicted 224-kDa precursor yet is observed on SDS-PAGE as a 190-kDa protein. A small rOmpA fragment of ∼32 kDa was discovered during surface proteome analysis and identified as the carboxy-terminal end of the protein. A rabbit polyclonal antibody was generated to the autotransporter region of rOmpA and confirmed a 32-kDa fragment corresponding to the calculated mass of a proteolytically cleaved rOmpA autotransporter region. N-terminal amino acid sequencing revealed a cleavage site on the carboxy-terminal side of Ser-1958 in rOmpA. An avirulent strain of R. rickettsii Iowa deficient in rOmpB processing was also defective in the processing of rOmpA. The similarities of the cleavage sites and the failure of R. rickettsii Iowa to process either rOmpA or rOmpB suggest that a single enzyme may be responsible for both processing events. IMPORTANCE Members of the spotted fever group of rickettsiae, including R. rickettsii, the etiologic agent of Rocky Mountain spotted fever, express at least four autotransporter proteins that are protective antigens or putative virulence determinants. One member of this class of proteins, rOmpB, is proteolytically processed to a passenger domain and an autotransporter domain that remain associated on the rickettsial outer membrane. The protease responsible for this posttranslation processing remains unknown. Here we show that another autotransporter, rOmpA, is similarly processed by R. rickettsii. Similarities in sequence at the cleavage site and predicted secondary protein structure suggest that all four R. rickettsii autotransporters may be processed by the same outer membrane protease.

scholarly journals Molecular Detection of Spotted Fever Group Rickettsiae (Rickettsiales: Rickettsiaceae) in Dermacentor variabilis (Acari: Ixodidae) Collected Along the Platte River in South Central Nebraska

2019 ◽  
Vol 57 (2) ◽  
pp. 519-523
Author(s):  
Brandon E Luedtke ◽  
Julie J Shaffer ◽  
Estrella Monrroy ◽  
Corey W Willicott ◽  
Travis J Bourret
Keyword(s):  
Spotted Fever ◽  
Rocky Mountain ◽  
Dermacentor Variabilis ◽  
Amblyomma Americanum ◽  
Spotted Fever Group ◽  
Rocky Mountain Spotted Fever ◽  
Rickettsia Species ◽  
Platte River ◽  
Rickettsia Rickettsii ◽  
South Central

Abstract Dermacentor variabilis is the predominant tick species in Nebraska and is presumed to be the primary vector of Rickettsia rickettsii associated with cases of Rocky Mountain spotted fever (RMSF). Interestingly, RMSF cases in Nebraska have increased on a year-to-year basis, yet the prevalence of R. rickettsii in D. variabilis ticks has not been established for Nebraska. Here we sought to set a baseline for the prevalence of R. rickettsii and other spotted fever group (SFG) rickettsiae harbored by D. variabilis ticks. Over a 3-yr period, D. variabilis were collected along the Platte River in south central Nebraska. Individual tick DNA was analyzed using endpoint PCR to identify ticks carrying SFG rickettsiae. In total, 927 D. variabilis were analyzed by PCR and 38 (4.1%) ticks tested positive for SFG rickettsiae. Presumptive positives were sequenced to identify the Rickettsia species, of which 29 (76%) were R. montanensis, 5 (13%) were R. amblyommatis, 4 (11%) were R. bellii, and R. rickettsii was not detected. These data indicate that R. rickettsii is likely at a low prevalence in south central Nebraska and spillover of R. amblyommatis into D. variabilis is likely occurring due to the invasive lone star tick (Amblyomma americanum). In addition, our data suggest that R. montanensis and R. amblyommatis could be associated with the increase in SFG rickettsiae infections in Nebraska. This information will be of value to clinicians and the general public for evaluating diagnosis of disease- and risk-associated environmental exposure, respectively.

scholarly journals Disruption of the Rickettsia rickettsii Sca2 Autotransporter Inhibits Actin-Based Motility

2010 ◽  
Vol 78 (5) ◽  
pp. 2240-2247 ◽  
Author(s):  
Betsy Kleba ◽  
Tina R. Clark ◽  
Erika I. Lutter ◽  
Damon W. Ellison ◽  
Ted Hackstadt
Keyword(s):  
Spotted Fever ◽  
Insertion Site ◽  
Rocky Mountain ◽  
Etiologic Agent ◽  
Spotted Fever Group ◽  
Rocky Mountain Spotted Fever ◽  
Spotted Fever Group Rickettsiae ◽  
Rickettsia Rickettsii ◽  
Transposon Insertion ◽  
Guinea Pig Model

ABSTRACT Rickettsii rickettsii, the etiologic agent of Rocky Mountain spotted fever, replicates within the cytosol of infected cells and uses actin-based motility to spread inter- and intracellularly. Although the ultrastructure of the actin tail and host proteins associated with it are distinct from those of Listeria or Shigella, comparatively little is known regarding the rickettsial proteins involved in its organization. Here, we have used random transposon mutagenesis of R. rickettsii to generate a small-plaque mutant that is defective in actin-based motility and does not spread directly from cell to cell as is characteristic of spotted fever group rickettsiae. The transposon insertion site of this mutant strain was within Sca2, a member of a family of large autotransporter proteins. Sca2 exhibits several features suggestive of its apparent role in actin-based motility. It displays an N-terminal secretory signal peptide, a C-terminal predicted autotransporter domain, up to four predicted Wasp homology 2 (WH2) domains, and two proline-rich domains, one with similarity to eukaryotic formins. In a guinea pig model of infection, the Sca2 mutant did not elicit fever, suggesting that Sca2 and actin-based motility are virulence factors of spotted fever group rickettsiae.

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