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.

Department of Rickettsiology Biomedical Research Center Slovak Academy of Sciences Dúbravská cesta 9 845 05 Bratislava Slovakia

Laboratory of Molecular Structure Characterization Institute of Microbiology Czech Academy of Sciences Vídeňská 1038 142 20 Prague Czech Republic

Zobrazit více v PubMed

Schriefer M.E., Sacci J.B., Dumler J.S., Bullen M.G., Azad A.F. Identification of a novel rickettsial infection in a patient diagnosed with murine typhus. J. Clin. Microbiol. 1994;32:949–954. doi: 10.1128/jcm.32.4.949-954.1994. PubMed DOI PMC

Abdad M.Y., Stenos J., Graves S. Rickettsia felis, an emerging flea-transmitted human pathogen. Emerg. Health Threat. J. 2011;4:7168. doi: 10.3402/ehtj.v4i0.7168. PubMed DOI PMC

Blanton L.S., Walker D.H. Flea-Borne Rickettsioses and Rickettsiae. Am. J. Trop. Med. Hyg. 2017;96:53–56. doi: 10.4269/ajtmh.16-0537. PubMed DOI PMC

Azad A.F., Radulovic S., Higgins J.A., Noden B.H., Troyer J.M. Flea-borne rickettsioses: Ecologic considerations. Emerg. Infect. Dis. 1997;3:319–327. doi: 10.3201/eid0303.970308. PubMed DOI PMC

Zavala-Velázquez J.E., Ruiz-Sosa J.A., Sánchez-Elias R.A., Becerra-Carmona G., Walker D.H. Rickettsia felis rickettsiosis in Yucatán. Lancet. 2000;356:1079–1080. doi: 10.1016/S0140-6736(00)02735-5. PubMed DOI

Lindblom A., Severinson K., Nilsson K. Rickettsia felis infection in Sweden: Report of two cases with subacute meningitis and review of the literature. Scand. J. Infect. Dis. 2010;42:906–909. doi: 10.3109/00365548.2010.508466. PubMed DOI

Mawuntu A.H.P., Johar E., Anggraeni R., Feliana F., Bernadus J.B.B., Safari D., Yudhaputri F.A., Dhenni R., Dewi Y.P., Kato C., et al. Rickettsia felis identified in two fatal cases of acute meningoencephalitis. PLoS Negl. Trop. Dis. 2020;14:e0007893. doi: 10.1371/journal.pntd.0007893. PubMed DOI PMC

Pérez-Osorio C.E., Zavala-Velázquez J.E., Arias León J.J., Zavala-Castro J.E. Rickettsia felis as emergent global threat for humans. Emerg. Infect. Dis. 2008;14:1019–1023. doi: 10.3201/eid1407.071656. PubMed DOI PMC

Angelakis E., Mediannikov O., Parola P., Raoult D. Rickettsia felis: The Complex Journey of an Emergent Human Pathogen. Trends Parasitol. 2016;32:554–564. doi: 10.1016/j.pt.2016.04.009. PubMed DOI

Parola P. Rickettsia felis: From a rare disease in the USA to a common cause of fever in sub-Saharan Africa. Clin. Microbiol. Infect. 2011;17:996–1000. doi: 10.1111/j.1469-0691.2011.03516.x. PubMed DOI

Márquez F.J., Muniain M.A., Pérez J.M., Pachón J. Presence of Rickettsia felis in the cat flea from southwestern Europe. Emerg. Infect. Dis. 2002;8:89–91. doi: 10.3201/eid0801.010193. PubMed DOI PMC

Reif K.E., Macaluso K.R. Ecology of Rickettsia felis: A review. J. Med. Entomol. 2009;46:723–736. doi: 10.1603/033.046.0402. PubMed DOI

Brown L.D., Macaluso K.R. Rickettsia felis, an Emerging Flea-Borne Rickettsiosis. Curr. Trop. Med. Rep. 2016;3:27–39. doi: 10.1007/s40475-016-0070-6. PubMed DOI PMC

Cardoso L.D., Freitas R.N., Mafra C.L., Neves C.V., Figueira F.C., Labruna M.B., Gennari S.M., Walker D.H., Galvão M.A. Characterization of Rickettsia spp. circulating in a silent peri-urban focus for Brazilian spotted fever in Caratinga, Minas Gerais, Brazil. Cad. Saude Publica. 2006;22:495–501. doi: 10.1590/S0102-311X2006000300004. PubMed DOI

Oliveira K.A., Oliveira L.S., Dias C.C., Silva A., Almeida M.R., Almada G., Bouyer D.H., Galvão M.A., Mafra C. Molecular identification of Rickettsia felis in ticks and fleas from an endemic area for Brazilian Spotted Fever. Mem. Inst. Oswaldo Cruz. 2008;103:191–194. doi: 10.1590/S0074-02762008000200011. PubMed DOI

Toledo A., Olmeda A.S., Escudero R., Jado I., Valcárcel F., Casado-Nistal M.A., Rodríguez-Vargas M., Gil H., Anda P. Tick-borne zoonotic bacteria in ticks collected from central Spain. Am. J. Trop. Med. Hyg. 2009;81:67–74. doi: 10.4269/ajtmh.2009.81.67. PubMed DOI

Abarca K., López J., Acosta-Jamett G., Martínez-Valdebenito C. Rickettsia felis in Rhipicephalus sanguineus from two distant Chilean cities. Vector Borne Zoonotic Dis. 2013;13:607–609. doi: 10.1089/vbz.2012.1201. PubMed DOI

Zhang J., Lu G., Kelly P., Zhang Z., Wei L., Yu D., Kayizha S., Wang C. First report of Rickettsia felis in China. BMC Infect. Dis. 2014;14:682. doi: 10.1186/s12879-014-0682-1. PubMed DOI PMC

Nguyen V.L., Colella V., Greco G., Fang F., Nurcahyo W., Hadi U.K., Venturina V., Tong K.B.Y., Tsai Y.L., Taweethavonsawat P., et al. Molecular detection of pathogens in ticks and fleas collected from companion dogs and cats in East and Southeast Asia. Parasites Vectors. 2020;13:420. doi: 10.1186/s13071-020-04288-8. PubMed DOI PMC

Campos S.D.E., Cunha N.C.D., Machado C.S.C., Telleria E.L., Cordeiro M.D., Fonseca A.H.D., Toma H.K., Santos J.P.C.D., Almosny N.R.P. Rickettsial pathogens circulating in urban districts of Rio de Janeiro, without report of human Brazilian Spotted Fever. Rev. Bras. Parasitol. Vet. 2020;29:e014220. doi: 10.1590/s1984-29612020082. PubMed DOI

de Oliveira J.C.P., Reckziegel G.H., Ramos C.A.D.N., Giannelli A., Alves L.C., de Carvalho G.A., Ramos R.A.N. Detection of Rickettsia felis in ectoparasites collected from domestic animals. Exp. Appl. Acarol. 2020;81:255–264. doi: 10.1007/s10493-020-00505-2. PubMed DOI

Gargili A., Palomar A.M., Midilli K., Portillo A., Kar S., Oteo J.A. Rickettsia species in ticks removed from humans in Istanbul, Turkey. Vector Borne Zoonotic Dis. 2012;12:938–941. doi: 10.1089/vbz.2012.0996. PubMed DOI PMC

Raele D.A., Galante D., Pugliese N., Salandra G., Cafiero M.A. Spotted fever group rickettsiae associated with ixodid ticks in wild environment in Southern Italy. Microbiologyopen. 2018;7:e00527. doi: 10.1002/mbo3.527. PubMed DOI PMC

Ishikura M., Ando S., Shinagawa Y., Matsuura K., Hasegawa S., Nakayama T., Fujita H., Watanabe M. Phylogenetic analysis of spotted fever group rickettsiae based on gltA, 17-kDa, and rOmpA genes amplified by nested PCR from ticks in Japan. Microbiol. Immunol. 2003;47:823–832. doi: 10.1111/j.1348-0421.2003.tb03448.x. PubMed DOI

Duh D., Punda-Polić V., Trilar T., Petrovec M., Bradarić N., Avsic-Zupanc T. Molecular identification of Rickettsia felis-like bacteria in Haemaphysalis sulcata ticks collected from domestic animals in southern Croatia. Ann. N. Y. Acad. Sci. 2006;1078:347–351. doi: 10.1196/annals.1374.068. PubMed DOI

Roth T., Lane R.S., Foley J. A Molecular Survey for Francisella tularensis and Rickettsia spp. in Haemaphysalis leporispalustris (Acari: Ixodidae) in Northern California. J. Med. Entomol. 2017;54:492–495. doi: 10.1093/jme/tjw202. PubMed DOI

Khoo J.J., Chen F., Kho K.L., Shanizza A.I.A., Lim F.S., Tan K.K., Chang L.Y., AbuBakar S. Bacterial community in Haemaphysalis ticks of domesticated animals from the Orang Asli communities in Malaysia. Ticks Tick Borne Dis. 2016;7:929–937. doi: 10.1016/j.ttbdis.2016.04.013. PubMed DOI

Chalada M.J., Stenos J., Vincent G., Barker D., Bradbury R.S. A Molecular Survey of Tick-Borne Pathogens from Ticks Collected in Central Queensland, Australia. Vector Borne Zoonotic Dis. 2018;18:151–163. doi: 10.1089/vbz.2017.2182. PubMed DOI

Jiang J., Stromdahl E.Y., Richards A.L. Detection of Rickettsia parkeri and Candidatus Rickettsia andeanae in Amblyomma maculatum Gulf Coast ticks collected from humans in the United States. Vector Borne Zoonotic Dis. 2012;12:175–182. doi: 10.1089/vbz.2011.0614. PubMed DOI

Soares H.S., Barbieri A.R., Martins T.F., Minervino A.H., de Lima J.T., Marcili A., Gennari S.M., Labruna M.B. Ticks and rickettsial infection in the wildlife of two regions of the Brazilian Amazon. Exp. Appl. Acarol. 2015;65:125–140. doi: 10.1007/s10493-014-9851-6. PubMed DOI

Bitencourth K., Amorim M., DE Oliveira S.V., Caetano R.L., Voloch C.M., Gazêta G.S. Amblyomma sculptum: Genetic diversity and rickettsias in the Brazilian Cerrado biome. Med. Vet. Entomol. 2017;31:427–437. doi: 10.1111/mve.12249. PubMed DOI

Bitencourth K., Amorim M., de Oliveira S.V., Voloch C.M., Gazêta G.S. Genetic diversity, population structure and rickettsias in Amblyomma ovale in areas of epidemiological interest for spotted fever in Brazil. Med. Vet. Entomol. 2019;33:256–268. doi: 10.1111/mve.12363. PubMed DOI

Tsui P.Y., Tsai K.H., Weng M.H., Hung Y.W., Liu Y.T., Hu K.Y., Lien J.C., Lin P.R., Shaio M.F., Wang H.C., et al. Molecular detection and characterization of spotted fever group rickettsiae in Taiwan. Am. J. Trop. Med. Hyg. 2007;77:883–890. doi: 10.4269/ajtmh.2007.77.883. PubMed DOI

Pascucci I., Di Domenico M., Curini V., Cocco A., Averaimo D., D’Alterio N., Cammà C. Diversity of Rickettsia in Ticks Collected in Abruzzi and Molise Regions (Central Italy) Microorganisms. 2019;7:696. doi: 10.3390/microorganisms7120696. PubMed DOI PMC

Dobler G., Wölfel R. Typhus and other rickettsioses: Emerging infections in Germany. Dtsch. Arztebl. Int. 2009;106:348–354. doi: 10.3238/arztebl.2009.0348. PubMed DOI PMC

Lejal E., Marsot M., Chalvet-Monfray K., Cosson J.F., Moutailler S., Vayssier-Taussat M., Pollet T. A three-years assessment of Ixodes ricinus-borne pathogens in a French peri-urban forest. Parasites Vectors. 2019;12:551. doi: 10.1186/s13071-019-3799-7. PubMed DOI PMC

Lejal E., Moutailler S., Šimo L., Vayssier-Taussat M., Pollet T. Tick-borne pathogen detection in midgut and salivary glands of adult Ixodes ricinus. Parasites Vectors. 2019;12:152. doi: 10.1186/s13071-019-3418-7. PubMed DOI PMC

Remesar S., Díaz P., Portillo A., Santibáñez S., Prieto A., Díaz-Cao J.M., López C.M., Panadero R., Fernández G., Díez-Baños P., et al. Prevalence and molecular characterization of Rickettsia spp. in questing ticks from north-western Spain. Exp. Appl. Acarol. 2019;79:267–278. doi: 10.1007/s10493-019-00426-9. PubMed DOI

Borşan S.D., Ionică A.M., Galon C., Toma-Naic A., Peştean C., Sándor A.D., Moutailler S., Mihalca A.D. High Diversity, Prevalence, and Co-infection Rates of Tick-Borne Pathogens in Ticks and Wildlife Hosts in an Urban Area in Romania. Front. Microbiol. 2021;12:645002. doi: 10.3389/fmicb.2021.645002. PubMed DOI PMC

Banović P., Díaz-Sánchez A.A., Galon C., Simin V., Mijatović D., Obregón D., Moutailler S., Cabezas-Cruz A. Humans infested with Ixodes ricinus are exposed to a diverse array of tick-borne pathogens in Serbia. Ticks Tick Borne Dis. 2021;12:101609. doi: 10.1016/j.ttbdis.2020.101609. PubMed DOI

Díaz-Sánchez A.A., Chilton N.B., Roblejo-Arias L., Fonseca-Rodríguez O., Marrero-Perera R., Diyes C.P., Yunik M.E.M., Lobo-Rivero E., Corona-González B. Molecular detection and identification of spotted fever group rickettsiae in ticks collected from horses in Cuba. Med. Vet. Entomol. 2021;35:207–212. doi: 10.1111/mve.12480. PubMed DOI

Stanley H., Rhodes D.V.L. Presence of Rickettsia Species in Ticks Collected from Companion Animals in Northeastern Georgia, United States. Vet. Sci. 2021;8:37. doi: 10.3390/vetsci8030037. PubMed DOI PMC

Reeves W.K., Loftis A.D., Sanders F., Spinks M.D., Wills W., Denison A.M., Dasch G.A. Borrelia, Coxiella, and Rickettsia in Carios capensis (Acari: Argasidae) from a brown pelican (Pelecanus occidentalis) rookery in South Carolina, USA. Exp. Appl. Acarol. 2006;39:321–329. doi: 10.1007/s10493-006-9012-7. PubMed DOI

Špitalská E., Boldiš V., Mošanský L., Sparagano O., Stanko M. Rickettsia species in fleas collected from small mammals in Slovakia. Parasitol. Res. 2015;114:4333–4339. doi: 10.1007/s00436-015-4713-7. PubMed DOI

Heglasová I., Víchová B., Stanko M. Detection of Rickettsia spp. in Fleas Collected from Small Mammals in Slovakia, Central Europe. Vector Borne Zoonotic Dis. 2020;20:652–656. doi: 10.1089/vbz.2019.2567. PubMed DOI

Adams J.R., Schmidtmann E.T., Azad A.F. Infection of colonized cat fleas, Ctenocephalides felis (Bouché), with a rickettsia-like microorganism. Am. J. Trop. Med. Hyg. 1990;43:400–409. doi: 10.4269/ajtmh.1990.43.400. PubMed DOI

Radulovic S., Higgins J.A., Jaworski D.C., Dasch G.A., Azad A.F. Isolation, cultivation, and partial characterization of the ELB agent associated with cat fleas. Infect. Immun. 1995;63:4826–4829. doi: 10.1128/iai.63.12.4826-4829.1995. PubMed DOI PMC

Radulovic S., Higgins J.A., Jaworski D.C., Azad A.F. In vitro and in vivo antibiotic susceptibilities of ELB rickettsiae. Antimicrob. Agents Chemother. 1995;39:2564–2566. doi: 10.1128/AAC.39.11.2564. PubMed DOI PMC

Higgins J.A., Radulovic S., Schriefer M.E., Azad A.F. Rickettsia felis: A new species of pathogenic rickettsia isolated from cat fleas. J. Clin. Microbiol. 1996;34:671–674. doi: 10.1128/jcm.34.3.671-674.1996. PubMed DOI PMC

Bouyer D.H., Stenos J., Crocquet-Valdes P., Moron C.G., Popov V.L., Zavala-Velazquez J.E., Foil L.D., Stothard D.R., Azad A.F., Walker D.H. Rickettsia felis: Molecular characterization of a new member of the spotted fever group. Int. J. Syst. Evol. Microbiol. 2001;51:339–347. doi: 10.1099/00207713-51-2-339. PubMed DOI

Raoult D., La Scola B., Enea M., Fournier P.E., Roux V., Fenollar F., Galvao M.A., de Lamballerie X. A flea-associated Rickettsia pathogenic for humans. Emerg. Infect. Dis. 2001;7:73–81. doi: 10.3201/eid0701.010112. PubMed DOI PMC

La Scola B., Meconi S., Fenollar F., Rolain J.M., Roux V., Raoult D. Emended description of Rickettsia felis (Bouyer et al. 2001), a temperature-dependent cultured bacterium. Int. J. Syst. Evol. Microbiol. 2002;52:2035–2041. doi: 10.1099/00207713-52-6-2035. PubMed DOI

Hii S.F., Abdad M.Y., Kopp S.R., Stenos J., Rees R.L., Traub R.J. Seroprevalence and risk factors for Rickettsia felis exposure in dogs from Southeast Queensland and the Northern Territory, Australia. Parasites Vectors. 2013;6:159. doi: 10.1186/1756-3305-6-159. PubMed DOI PMC

Ng-Nguyen D., Hii S.F., Hoang M.T., Nguyen V.T., Rees R., Stenos J., Traub R.J. Domestic dogs are mammalian reservoirs for the emerging zoonosis flea-borne spotted fever, caused by Rickettsia felis. Sci. Rep. 2020;10:4151. doi: 10.1038/s41598-020-61122-y. PubMed DOI PMC

Pornwiroon W., Pourciau S.S., Foil L.D., Macaluso K.R. Rickettsia felis from cat fleas: Isolation and culture in a tick-derived cell line. Appl. Environ. Microbiol. 2006;72:5589–5595. doi: 10.1128/AEM.00532-06. PubMed DOI PMC

Thepparit C., Sunyakumthorn P., Guillotte M.L., Popov V.L., Foil L.D., Macaluso K.R. Isolation of a rickettsial pathogen from a non-hematophagous arthropod. PLoS ONE. 2011;6:e16396. doi: 10.1371/journal.pone.0016396. PubMed DOI PMC

Horta M.C., Labruna M.B., Durigon E.L., Schumaker T.T. Isolation of Rickettsia felis in the mosquito cell line C6/36. Appl. Environ. Microbiol. 2006;72:1705–1707. doi: 10.1128/AEM.72.2.1705-1707.2006. PubMed DOI PMC

Hun L., Troyo A., Taylor L., Barbieri A.M., Labruna M.B. First report of the isolation and molecular characterization of Rickettsia amblyommii and Rickettsia felis in Central America. Vector Borne Zoonotic Dis. 2011;11:1395–1397. doi: 10.1089/vbz.2011.0641. PubMed DOI

Sakamoto J.M., Azad A.F. Propagation of arthropod-borne Rickettsia spp. in two mosquito cell lines. Appl. Environ. Microbiol. 2007;73:6637–6643. doi: 10.1128/AEM.00923-07. PubMed DOI PMC

Luce-Fedrow A., Macaluso K.R., Richards A.L. Growth of Rickettsia felis in Drosophila melanogaster S2 cells. Vector Borne Zoonotic Dis. 2014;14:101–110. doi: 10.1089/vbz.2013.1370. PubMed DOI

Saisongkorh W., El Karkouri K., Patrice J.Y., Bernard A., Rolain J.M., Raoult D. Tryptose phosphate broth improves Rickettsia felis replication in mammalian cells. FEMS Immunol. Med. Microbiol. 2012;64:111–114. doi: 10.1111/j.1574-695X.2011.00882.x. PubMed DOI

Segura F., Pons I., Pla J., Nogueras M.M. Shell-vial culture and real-time PCR applied to Rickettsia typhi and Rickettsia felis detection. World J. Microbiol. Biotechnol. 2015;31:1747–1754. doi: 10.1007/s11274-015-1925-z. PubMed DOI

Stevenson H.L., Labruna M.B., Montenieri J.A., Kosoy M.Y., Gage K.L., Walker D.H. Detection of Rickettsia felis in a New World flea species, Anomiopsyllus nudata (Siphonaptera: Ctenophthalmidae) J. Med. Entomol. 2005;42:163–167. doi: 10.1093/jmedent/42.2.163. PubMed DOI

Nosek J., Sixl W. Central-European ticks (Ixodoidea). Key for determination. Mitt. Abt. Zool. Landesmus. Joanneum. 1972;1:61–92.

Sekeyová Z., Mediannikov O., Subramanian G., Kowalczewska M., Quevedo-Diaz M., Kocianová E., Raoult D. Isolation of rickettsia helvetica from ticks in Slovakia. Acta Virol. 2012;56:247–252. doi: 10.4149/av_2012_03_247. PubMed DOI

Pudney M., Varma M.G., Leake C.J. Establishment of a cell line (XTC-2) from the South African clawed toad, Xenopus laevis. Experientia. 1973;29:466–467. doi: 10.1007/BF01926785. PubMed DOI

Giménez D.F. Staining Rickettsiae in Yolk-Sac Cultures. Stain Technol. 1964;39:135–140. doi: 10.3109/10520296409061219. PubMed DOI

Ammerman N.C., Beier-Sexton M., Azad A.F. Laboratory maintenance of Rickettsia rickettsii. Curr. Protoc. Microbiol. 2008;11:3A.5.1–3A.5.21. doi: 10.1002/9780471729259.mc03a05s11. PubMed DOI PMC

Weiss E., Coolbaugh J.C., Williams J.C. Separation of viable Rickettsia typhi from yolk sac and L cell host components by renografin density gradient centrifugation. Appl. Microbiol. 1975;30:456–463. doi: 10.1128/am.30.3.456-463.1975. PubMed DOI PMC

Bohacsova M., Filipcik P., Opattova A., Valarikova J., Diaz M.Q., Skultety L., Novak M., Sekeyova Z. Survival of rat cerebrocortical neurons after rickettsial infection. Microbes Infect. 2015;17:845–849. doi: 10.1016/j.micinf.2015.09.024. PubMed DOI

Valarikova J., Sekeyova Z., Skultety L., Bohacsova M., Quevedo-Diaz M. New way of purification of pathogenic rickettsiae reducing health risks. Acta Virol. 2016;60:206–210. doi: 10.4149/av_2016_02_206. PubMed DOI

Roux V., Raoult D. Phylogenetic analysis of the genus Rickettsia by 16S rDNA sequencing. Res. Microbiol. 1995;146:385–396. doi: 10.1016/0923-2508(96)80284-1. PubMed DOI

Al Masalma M., Armougom F., Scheld W.M., Dufour H., Roche P.H., Drancourt M., Raoult D. The expansion of the microbiological spectrum of brain abscesses with use of multiple 16S ribosomal DNA sequencing. Clin. Infect. Dis. 2009;48:1169–1178. doi: 10.1086/597578. PubMed DOI

Sekeyova Z., Roux V., Raoult D. Phylogeny of Rickettsia spp. inferred by comparing sequences of ’gene D’, which encodes an intracytoplasmic protein. Int. J. Syst. Evol. Microbiol. 2001;51:1353–1360. doi: 10.1099/00207713-51-4-1353. PubMed DOI

Labruna M.B., Whitworth T., Horta M.C., Bouyer D.H., McBride J.W., Pinter A., Popov V., Gennari S.M., Walker D.H. Rickettsia species infecting Amblyomma cooperi ticks from an area in the state of São Paulo, Brazil, where Brazilian spotted fever is endemic. J. Clin. Microbiol. 2004;42:90–98. doi: 10.1128/JCM.42.1.90-98.2004. PubMed DOI PMC

Roux V., Rydkina E., Eremeeva M., Raoult D. Citrate synthase gene comparison, a new tool for phylogenetic analysis, and its application for the rickettsiae. Int. J. Syst. Bacteriol. 1997;47:252–261. doi: 10.1099/00207713-47-2-252. PubMed DOI

Zavala-Castro J.E., Small M., Keng C., Bouyer D.H., Zavala-Velázquez J., Walker D.H. Transcription of the Rickettsia felis ompA gene in naturally infected fleas. Am. J. Trop. Med. Hyg. 2005;73:662–666. doi: 10.4269/ajtmh.2005.73.662. PubMed DOI PMC

Roux V., Raoult D. Phylogenetic analysis of members of the genus Rickettsia using the gene encoding the outer-membrane protein rOmpB (ompB) Int. J. Syst. Evol. Microbiol. 2000;50:1449–1455. doi: 10.1099/00207713-50-4-1449. PubMed DOI

Drancourt M., Raoult D. Characterization of mutations in the rpoB gene in naturally rifampin-resistant Rickettsia species. Antimicrob. Agents Chemother. 1999;43:2400–2403. doi: 10.1128/AAC.43.10.2400. PubMed DOI PMC

Boretti F.S., Perreten A., Meli M.L., Cattori V., Willi B., Wengi N., Hornok S., Honegger H., Hegglin D., Woelfel R., et al. Molecular Investigations of Rickettsia helvetica infection in dogs, foxes, humans, and Ixodes ticks. Appl. Environ. Microbiol. 2009;75:3230–3237. doi: 10.1128/AEM.00220-09. PubMed DOI PMC

Fournier P.E., Belghazi L., Robert C., Elkarkouri K., Richards A.L., Greub G., Collyn F., Ogawa M., Portillo A., Oteo J.A., et al. Variations of plasmid content in Rickettsia felis. PLoS ONE. 2008;3:e2289. doi: 10.1371/annotation/6870e918-77d7-4ef5-ae5e-6cf994f9c169. PubMed DOI PMC

Hall T.A. BioEdit: A user-friendly biological sequence alignment editor and analysis program for Windows 95/98/NT. Nucleic. Acids Symp. Ser. 1999;41:95–98.

Danchenko M., Csaderova L., Fournier P.E., Sekeyova Z. Optimized fixation of actin filaments for improved indirect immunofluorescence staining of rickettsiae. BMC Res. Notes. 2019;12:657. doi: 10.1186/s13104-019-4699-9. PubMed DOI PMC

Sobue K., Fujio Y., Kanda K. Tumor promoter induces reorganization of actin filaments and calspectin (fodrin or nonerythroid spectrin) in 3T3 cells. Proc. Natl. Acad. Sci. USA. 1988;85:482–486. doi: 10.1073/pnas.85.2.482. PubMed DOI PMC

Benada O., Pokorný V. Modification of the Polaron sputter-coater unit for glow-discharge activation of carbon support films. J. Electron. Microsc. Tech. 1990;16:235–239. doi: 10.1002/jemt.1060160304. PubMed DOI

Sekeyová Z., Fournier P.E., Rehácek J., Raoult D. Characterization of a new spotted fever group rickettsia detected in Ixodes ricinus (Acari: Ixodidae) collected in Slovakia. J. Med. Entomol. 2000;37:707–713. doi: 10.1093/jmedent/37.5.707. PubMed DOI

Boldis V., Strus J., Kocianová E., Tusek-Znidaric M., Stefanidesová K., Schwarzová K., Kúdelová M., Sekeyová Z., Spitalská E. Life cycle of Rickettsia slovaca in L929 cell line studied by quantitative real-time PCR and transmission electron microscopy. FEMS Microbiol. Lett. 2009;293:102–106. doi: 10.1111/j.1574-6968.2009.01510.x. PubMed DOI

Mediannikov O., Sekeyová Z., Birg M.L., Raoult D. A novel obligate intracellular gamma-proteobacterium associated with ixodid ticks, Diplorickettsia massiliensis, Gen. Nov., sp. Nov. PLoS ONE. 2010;5:e11478. doi: 10.1371/journal.pone.0011478. PubMed DOI PMC

Mediannikov O., Subramanian G., Sekeyova Z., Bell-Sakyi L., Raoult D. Isolation of Arsenophonus nasoniae from Ixodes ricinus ticks in Slovakia. Ticks Tick Borne Dis. 2012;3:367–370. doi: 10.1016/j.ttbdis.2012.10.016. PubMed DOI

Spitalská E., Stefanidesová K., Kocianová E., Boldiš V. Rickettsia slovaca and Rickettsia raoultii in Dermacentor marginatus and Dermacentor reticulatus ticks from Slovak Republic. Exp. Appl. Acarol. 2012;57:189–197. doi: 10.1007/s10493-012-9539-8. PubMed DOI

Špitalská E., Boldiš V., Derdáková M., Selyemová D., Rusňáková Taragel’ová V. Rickettsial infection in Ixodes ricinus ticks in urban and natural habitats of Slovakia. Ticks Tick Borne Dis. 2014;5:161–165. doi: 10.1016/j.ttbdis.2013.10.002. PubMed DOI

Svehlová A., Berthová L., Sallay B., Boldiš V., Sparagano O.A., Spitalská E. Sympatric occurrence of Ixodes ricinus, Dermacentor reticulatus and Haemaphysalis concinna ticks and Rickettsia and Babesia species in Slovakia. Ticks Tick Borne Dis. 2014;5:600–605. doi: 10.1016/j.ttbdis.2014.04.010. PubMed DOI

Špitalská E., Stanko M., Mošanský L., Kraljik J., Miklisová D., Mahríková L., Bona M., Kazimírová M. Seasonal analysis of Rickettsia species in ticks in an agricultural site of Slovakia. Exp. Appl. Acarol. 2016;68:315–324. doi: 10.1007/s10493-015-9941-0. PubMed DOI

Berthová L., Slobodník V., Slobodník R., Olekšák M., Sekeyová Z., Svitálková Z., Kazimírová M., Špitalská E. The natural infection of birds and ticks feeding on birds with Rickettsia spp. and Coxiella burnetii in Slovakia. Exp. Appl. Acarol. 2016;68:299–314. doi: 10.1007/s10493-015-9975-3. PubMed DOI

Ogata H., Renesto P., Audic S., Robert C., Blanc G., Fournier P.E., Parinello H., Claverie J.M., Raoult D. The genome sequence of Rickettsia felis identifies the first putative conjugative plasmid in an obligate intracellular parasite. PLoS Biol. 2005;3:e248. doi: 10.1371/journal.pbio.0030248. PubMed DOI PMC

Gillespie J.J., Driscoll T.P., Verhoeve V.I., Utsuki T., Husseneder C., Chouljenko V.N., Azad A.F., Macaluso K.R. Genomic diversification in strains of Rickettsia felis Isolated from different arthropods. Genome Biol. Evol. 2014;7:35–56. doi: 10.1093/gbe/evu262. PubMed DOI PMC

Bitam I., Parola P., De La Cruz K.D., Matsumoto K., Baziz B., Rolain J.M., Belkaid M., Raoult D. First molecular detection of Rickettsia felis in fleas from Algeria. Am. J. Trop. Med. Hyg. 2006;74:532–535. doi: 10.4269/ajtmh.2006.74.532. PubMed DOI

Znazen A., Rolain J.M., Hammami A., Jemaa M.B., Raoult D. Rickettsia felis infection, Tunisia. Emerg. Infect. Dis. 2006;12:138–140. doi: 10.3201/eid1201.050876. PubMed DOI PMC

Fang R., Raoult D. Antigenic classification of Rickettsia felis by using monoclonal and polyclonal antibodies. Clin. Diagn. Lab. Immunol. 2003;10:221–228. doi: 10.1128/CDLI.10.2.221-228.2003. PubMed DOI PMC

Gray J.S., Kahl O., Lane R.S., Levin M.L., Tsao J.I. Diapause in ticks of the medically important Ixodes ricinus species complex. Ticks Tick-Borne Dis. 2016;7:992–1003. doi: 10.1016/j.ttbdis.2016.05.006. PubMed DOI PMC

Matuschka F.R., Fischer P., Musgrave K., Richter D., Spielman A. Hosts on which nymphal Ixodes ricinus most abundantly feed. Am. J. Trop. Med. Hyg. 1991;44:100–107. doi: 10.4269/ajtmh.1991.44.100. PubMed DOI

Fischer S., Spierling N.G., Heuser E., Kling C., Schmidt S., Rosenfeld U.M., Reil D., Imholt C., Jacob J., Ulrich R.G., et al. High prevalence of Rickettsia helvetica in wild small mammal populations in Germany. Ticks Tick Borne Dis. 2018;9:500–505. doi: 10.1016/j.ttbdis.2018.01.009. PubMed DOI

Schex S., Dobler G., Riehm J., Müller J., Essbauer S. Rickettsia spp. in wild small mammals in Lower Bavaria, South-Eastern Germany. Vector Borne Zoonotic Dis. 2011;11:493–502. doi: 10.1089/vbz.2010.0060. PubMed DOI

Riley P.Y., Chomel B.B. Hedgehog zoonoses. Emerg. Infect. Dis. 2005;11:1–5. doi: 10.3201/eid1101.040752. PubMed DOI PMC

Jahfari S., Ruyts S.C., Frazer-Mendelewska E., Jaarsma R., Verheyen K., Sprong H. Melting pot of tick-borne zoonoses: The European hedgehog contributes to the maintenance of various tick-borne diseases in natural cycles urban and suburban areas. Parasites Vectors. 2017;10:134. doi: 10.1186/s13071-017-2065-0. PubMed DOI PMC

Marié J.L., Davoust B., Socolovschi C., Raoult D., Parola P. Molecular detection of rickettsial agents in ticks and fleas collected from a European hedgehog (Erinaceus europaeus) in Marseilles, France. Comp. Immunol. Microbiol. Infect. Dis. 2012;35:77–79. doi: 10.1016/j.cimid.2011.11.005. PubMed DOI

Harris E.K., Verhoeve V.I., Banajee K.H., Macaluso J.A., Azad A.F., Macaluso K.R. Comparative vertical transmission of Rickettsia by Dermacentor variabilis and Amblyomma maculatum. Ticks Tick Borne Dis. 2017;8:598–604. doi: 10.1016/j.ttbdis.2017.04.003. PubMed DOI PMC