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Published on: October 11, 2022
Culture Isolate of Rickettsia felis from a Tick
Monika Danchenko1, Oldřich Benada2, Ľudovít Škultéty1,2
1Department of Rickettsiology, Biomedical Research Center, Slovak Academy of Sciences, Dúbravská cesta 9, 845 05 Bratislava, Slovakia.
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.
Insights
Researchers successfully cultured Rickettsia felis from the castor bean tick (Ixodes ricinus), a common tick species. This marks the first isolation of R. felis from a tick, opening new avenues for understanding tick-borne disease transmission.
Area of Science:
- Veterinary Entomology
- Bacteriology
- Molecular Biology
Background:
- The cat flea (Ctenocephalides felis) is the primary vector of Rickettsia felis.
- Other arthropods, including ticks, have been molecularly linked to R. felis, but their transmission role is unclear.
Purpose of the Study:
- To achieve the first successful culture isolation and characterization of Rickettsia felis from a tick vector.
- To investigate the potential of Ixodes ricinus as a reservoir and vector for R. felis.
Main Methods:
- Isolation of R. felis from a host-seeking Ixodes ricinus nymph using the shell-vial technique on XTC-2 cells.
- Microscopic observation (Gimenez staining, immunofluorescence), gradient ultracentrifugation, and electron microscopy for bacterial characterization.
- Genetic analysis of key R. felis genes and comparison with known strains.
Main Results:
- Successful isolation and culture of R. felis from an Ixodes ricinus tick.
- Characterization of the isolate, named "Danube", revealing genetic similarity to known strains but absence of plasmid pRFδ.
- Confirmation of R. felis presence in host cells via microscopy and genetic sequencing.
Conclusions:
- Ixodes ricinus can harbor and potentially transmit Rickettsia felis.
- This study provides the first evidence of culturable R. felis derived from a tick.
- Further research is needed to elucidate the role of ticks in R. felis epidemiology.
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