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Condit ME, Jones E, Biggerstaff BJ, Kato CY. Procedure for spotted fever group Rickettsia isolation from limited clinical blood specimens. PLoS Negl Trop Dis 2022; 16:e0010781. [PMID: 36240222 PMCID: PMC9605293 DOI: 10.1371/journal.pntd.0010781] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2021] [Revised: 10/26/2022] [Accepted: 08/30/2022] [Indexed: 11/20/2022] Open
Abstract
BACKGROUND Current isolation techniques for spotted fever group Rickettsia from clinical samples are laborious and are limited to tissue, blood and blood derivatives with volumes ideally greater than 1 mL. We validated the use of simplified methodologies for spotted fever group Rickettsia culture isolation that overcome sample volume limitations and provide utility in clinical diagnostics and research studies. METHODOLOGY/PRINCIPAL FINDINGS A modified cell culture method is evaluated for the isolation of Rickettsia ssp. from human diagnostic samples. Culture sampling method, culture platform, and growth phase analysis were evaluated to determine best practices for optimal culture isolation conditions. Rickettsial isolates (R. conorii, R. rickettsii, and R. parkeri) were grown in Vero E6 cells over a course of 5 to 7 days at low inoculum treatments (~40 bacterial copies) to standardize the sampling strategy at a copy number reflective of the bacteremia in acute diagnostic samples. This methodology was verified using small volumes (50 μL) of 25 unprocessed clinical whole blood, plasma, and serum samples from acute samples of patients suspected of having Rocky Mountain Spotted Fever, of which 10 were previously confirmed positive via the PanR8 qPCR assay, 13 had no detectable Rickettsia DNA by the PanR8 qPCR assay, and 2 were not previously tested; these samples resulted in the cultivation of 7 new R. rickettsii isolates. CONCLUSIONS/SIGNIFICANCE We observed that rickettsial isolate growth in culture is reproducibly identified by real-time PCR testing of culture media within 72 hours after inoculation. Additionally, specimen sedimentation prior to isolation to remove red blood cells was found to decrease the amount of total organism available in the inoculum. A small volume culture method was established focusing on comparative qPCR detection rather than bacterial visualization, taking significantly shorter time to detect, and requiring less manipulation compared to traditional clinical isolate culture methods.
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Affiliation(s)
- Marah E. Condit
- Rickettsial Zoonoses Branch, Division of Vector-Borne Diseases, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America
| | - Emma Jones
- Office of the Director, Division of Vector-Borne Diseases, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, Colorado, United States of America
| | - Brad J. Biggerstaff
- Office of the Director, Division of Vector-Borne Diseases, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, Colorado, United States of America
| | - Cecilia Y. Kato
- Rickettsial Zoonoses Branch, Division of Vector-Borne Diseases, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America,* E-mail:
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Culture Isolate of Rickettsia felis from a Tick. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2022; 19:ijerph19074321. [PMID: 35410003 PMCID: PMC8998211 DOI: 10.3390/ijerph19074321] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Revised: 03/28/2022] [Accepted: 03/31/2022] [Indexed: 02/04/2023]
Abstract
Although the cat flea, Ctenocephalides felis, has been identified as the primary vector of Rickettsia felis, additional flea, tick, mite, and louse species have also been associated with this bacterium by molecular means; however, the role of these arthropods in the transmission of R. felis has not been clarified. Here, we succeeded in culture isolation of R. felis from a host-seeking castor bean tick, Ixodes ricinus, the most common tick in Slovakia. The bacterial isolation was performed on XTC-2 cells at 28 °C using the shell-vial technique. An evaluation of the growth properties was performed for both the XTC-2 and Vero cell lines. We observed R. felis in the infected host cells microscopically by Gimenez staining and immunofluorescence assay. The R. felis isolate was purified by gradient ultracentrifugation and visualized by electron microscopy. Fragments of the genes gltA, ompA, ompB, htrA, rpoB, sca4, rffE, and rrs were amplified and compared with the corresponding sequences of the type strain URRWXCal2 and other R. felis culture -isolated strains. We did not detect any nucleotide polymorphisms; however, plasmid pRFδ, characteristic of the standard strain, was absent in our isolate. Herein, we describe the first successful isolation and characterization of a tick-derived R. felis strain “Danube”, obtained from an I. ricinus nymph.
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Zurita A, Benkacimi L, El Karkouri K, Cutillas C, Parola P, Laroche M. New records of bacteria in different species of fleas from France and Spain. Comp Immunol Microbiol Infect Dis 2021; 76:101648. [PMID: 33895462 DOI: 10.1016/j.cimid.2021.101648] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Revised: 03/24/2021] [Accepted: 03/30/2021] [Indexed: 11/16/2022]
Abstract
In this study, we assessed the presence of vector-borne microorganisms in different species of fleas collected from different hosts in diverse areas of South-Western Europe by molecular methods. A total of 319 fleas belonging to eight different species was tested for the presence of eight microorganisms. Wolbachia spp. endosymbionts were detected in Ctenocephalides felis, Pulex irritans, Archaeopsylla erinacei and Ctenophthalmus baeticus boisseauorum specimens. Rickettsia felis, an emerging pathogen, was detected in C. felis, A. erinacei and Ct. b. boisseauorum. Rickettsia typhi, the agent of murine typhus was detected for the first time in A. erinacei and Mycobacterium spp. were detected for the first time in fleas (C. felis, P. irritans and A. erinacei). Lastly, five different species of Bartonella were detected in fleas' DNA in this study, including a possible new bacterium belonging to this genus. With this study, we updated the knowledge of the flea-borne bacteria present in the South-West of Europe reinforcing the idea about the necessity to expand and increase the current knowledge on flea-borne pathogens.
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Affiliation(s)
- Antonio Zurita
- Department of Microbiology and Parasitology, Faculty of Pharmacy, University of Seville, Professor García González 2, 41012, Seville, Spain
| | - Linda Benkacimi
- IHU-Méditerranée Infection, Marseille, France; Aix Marseille Univ, IRD, AP-HM, SSA, VITROME, Marseille, France
| | - Khalid El Karkouri
- IHU-Méditerranée Infection, Marseille, France; Aix Marseille Univ, IRD, AP-HM, SSA, VITROME, Marseille, France
| | - Cristina Cutillas
- Department of Microbiology and Parasitology, Faculty of Pharmacy, University of Seville, Professor García González 2, 41012, Seville, Spain
| | - Philippe Parola
- IHU-Méditerranée Infection, Marseille, France; Aix Marseille Univ, IRD, AP-HM, SSA, VITROME, Marseille, France
| | - Maureen Laroche
- IHU-Méditerranée Infection, Marseille, France; Aix Marseille Univ, IRD, AP-HM, SSA, VITROME, Marseille, France.
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Abstract
Rickettsia are small, obligately intracellular, gram-negative bacilli. They are distributed among a variety of hematophagous arthropod vectors and cause illness throughout the world. Rickettsioses present as an acute undifferentiated febrile illness and are often accompanied by headache, myalgias, and malaise. Cutaneous manifestations include rash and eschar, which both occur at varying incidence depending on the infecting species. Serology is the mainstay of diagnosis, and the indirect immunofluorescence assay is the test of choice. Reactive antibodies are seldom present during early illness, so testing should be performed on both acute-phase and convalescent-phase sera. Doxycycline is the treatment of choice.
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Affiliation(s)
- Lucas S Blanton
- Department of Internal Medicine, Division of Infectious Diseases, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555-0435, USA.
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Kho KL, Tay ST. Identification of Rickettsial Infections (Rickettsia sp. TH2014) in Ctenocephalides orientis Fleas (Siphonaptera: Pulicidae). JOURNAL OF MEDICAL ENTOMOLOGY 2019; 56:526-532. [PMID: 30312440 DOI: 10.1093/jme/tjy169] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Indexed: 06/08/2023]
Abstract
Rickettsia felis (Rickettsiales: Rickettsiaceae) is an emergent human pathogen that causes febrile illnesses in various parts of the world. This study describes the identification and growth characteristics of a R. felis-like organism (designated as Rickettsia sp. TH2014) cultured from Ctenocephalides orientis fleas in rural Malaysia. In this study, culturing of rickettsiae from filtered triturated flea lysates was performed in Aedes albopictus C6/36 cells. Cytopathic effects were observed from one of the samples 4 d post-inoculation. Electron microscopy revealed actively replicating intracytosolic coccobacillary organisms in the rickettsia-infected cells. Sequence analysis of amplified citrate synthase (gltA) gene fragment shows complete match of the rickettsia with Rickettsia sp. Rf31 in Southeast Asia, and 'Candidatus Rickettsia senegalensis' strain PU01-02 in Africa. The whole-genome sequence of Rickettsia sp. TH2014 was determined and assembled. The estimated genome size and guanine + cytosine content of the rickettsia are 1.37 Mb and 32.9%, respectively. The high values of average nucleotide identity and tetra-nucleotide signature correlation index obtained from pairwise genome comparison study suggest the identification of the rickettsia as R. felis. The whole-genome single-nucleotide polymorphism analysis demonstrates close genetic relatedness of the rickettsia with R. felis and Rickettsia asemboensis. However, based on sequence analyses of rickettsial genes (16S rDNA, gltA, ompB, and sca4), Rickettsia sp. TH2014 is found to be distinct from R. felis and R. asemboensis. The sequence analyses reveal that Rickettsia sp. TH2014 is highly similar to 'Ca. Rickettsia senegalensis' detected in fleas from Africa, Asia, and North America. Further investigation to provide insights on pathogenic potential and transmission dynamics of the rickettsia is warranted.
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Affiliation(s)
- Kai Ling Kho
- Department of Medical Microbiology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
| | - Sun Tee Tay
- Department of Medical Microbiology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
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Abstract
With advances in molecular genetics, more pathogenic rickettsial species have been identified. Pathogenic rickettsiae are transmitted by vectors, such as arthropods, into the patient's skin and then spread into the microvascular endothelial cells. Clinical manifestations are characterized by fever with headache and myalgias, followed by rash 3 to 5 days later. The undifferentiated nature of clinical symptoms, knowledge of the epidemiology, and the patient's history of travel and exposure to arthropod vectors are critical to the empiric administration of antimicrobial therapy. Doxycycline is currently the most effective antibiotic for treatment of all spotted fever group and typhus group rickettsioses.
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Affiliation(s)
- Rong Fang
- Department of Pathology, The University of Texas Medical Branch at Galveston, 301 University Boulevard, Galveston, TX 77555-0609, USA
| | - Lucas S Blanton
- Infectious Diseases, Department of Internal Medicine, The University of Texas Medical Branch at Galveston, 301 University Boulevard, Galveston, TX 77555-0435, USA
| | - David H Walker
- Department of Pathology, Center for Biodefense and Emerging Infectious Diseases, The University of Texas Medical Branch, 301 University Boulevard, Keiller Building, Galveston, TX 77555-0609, USA.
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Angelakis E, Mediannikov O, Parola P, Raoult D. Rickettsia felis: The Complex Journey of an Emergent Human Pathogen. Trends Parasitol 2016; 32:554-564. [PMID: 27155905 DOI: 10.1016/j.pt.2016.04.009] [Citation(s) in RCA: 87] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Revised: 03/14/2016] [Accepted: 04/12/2016] [Indexed: 11/16/2022]
Abstract
Rickettsia felis is an obligate intracellular bacterium that is different from other officially recognized rickettsial species. It has multiple genes of different origins, an incubation temperature of less than 32°C, and a conjugative plasmid. This Rickettsia is commonly detected in febrile patients in sub-Saharan Africa. R. felis is frequently detected in cat fleas, but recently mosquitoes have been suspected to be able to transmit the bacterium. However, many aspects of the ecology and epidemiology of R. felis are not completely understood and remain to be uncovered. We aim here to give an update of the current knowledge about this fascinating organism.
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Affiliation(s)
- Emmanouil Angelakis
- URMITE, UM63, CNRS 7278, IRD 198, Inserm 1095, Aix Marseille Université, 27 Bd Jean Moulin, 13385 Marseille, France.
| | - Oleg Mediannikov
- URMITE, UM63, CNRS 7278, IRD 198, Inserm 1095, Aix Marseille Université, 27 Bd Jean Moulin, 13385 Marseille, France
| | - Philippe Parola
- URMITE, UM63, CNRS 7278, IRD 198, Inserm 1095, Aix Marseille Université, 27 Bd Jean Moulin, 13385 Marseille, France
| | - Didier Raoult
- URMITE, UM63, CNRS 7278, IRD 198, Inserm 1095, Aix Marseille Université, 27 Bd Jean Moulin, 13385 Marseille, France
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