Multispacer typing of Rickettsia isolates from humans and ticks in Tunisia revealing new genotypes
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Published on: October 11, 2022
Abir Znazen1, Fatma Khrouf, Nihel Elleuch
1Laboratory of Microbiology, Research Laboratory "MPH", Habib Bourguiba University Hospital of Sfax, Sfax, Tunisia. abirznazen2001@yahoo.fr.
Background:
Rickettsioses are important remerging vector born infections. In Tunisia, many species have been described in humans and vectors. Genotyping is important for tracking pathogen movement between hosts and vectors. In this study, we characterized Rickettsia species detected in patients and vectors using multispacer typing (MST), proposed by Founier et al. and based on three intergenic spacers (dksA-xerC, rmpE- tRNA(fMet), mppA-pruC) sequencing.
Methods:
Our study included 25 patients hospitalized during 2009. Ticks and fleas were collected in the vicinity of confirmed cases. Serology was performed on serum samples by microimmunofluorescence using Rickettsia conorii and Rickettsia typhi antigens. To detect and identify Rickettsia species, PCR targeting ompA, ompB and gltA genes followed by sequencing was performed on 18 obtained skin biopsies and on all collected vectors. Rickettsia positive samples were further characterized using primers targeting three intergenic spacers (dksA-xerC, rmpE- tRNA(fMet) and mppA-purC).
Results:
A rickettsial infection was confirmed in 15 cases (60%). Serology was positive in 13 cases (52%). PCR detected Rickettsia DNA in four biopsies (16%) allowing the identification of R. conorii subsp israelensis in three cases and R. conorii subsp conorii in one case. Among 380 collected ticks, nine presented positive PCR (2.4%) allowing the identification of six R. conorii subsp israelensis, two R. massiliae and one R. conorii subsp conorii. Among 322 collected fleas, only one was positive for R. felis. R. conorii subsp israelensis strains detected in humans and vectors clustered together and showed a new MST genotype. Similarly, R. conorii subsp conorii strains detected in a skin biopsy and a tick were genetically related and presented a new MST genotype.
Conclusions:
New Rickettsia spotted fever strain genotypes were found in Tunisia. Isolates detected in humans and vectors were genetically homogenous despite location differences in their original isolation suggesting epidemiologic circulation of these strains.
Insights
New Rickettsia genotypes were identified in Tunisia, with strains from humans and vectors showing genetic homogeneity. This suggests ongoing epidemiologic circulation of these emerging infectious agents.
Area of Science:
- Medical Microbiology
- Infectious Diseases
- Genetics
Background:
- Rickettsioses represent significant re-emerging vector-borne diseases.
- Multiple Rickettsia species have been identified in both human and vector populations in Tunisia.
- Molecular genotyping is crucial for tracing pathogen transmission dynamics between hosts and vectors.
Purpose of the Study:
- To characterize Rickettsia species in Tunisian patients and vectors.
- To employ multispacer typing (MST) for detailed genetic analysis of Rickettsia isolates.
- To investigate the genetic relatedness of Rickettsia strains found in humans and arthropod vectors.
Main Methods:
- Collected samples from 25 patients and vectors (ticks and fleas) in Tunisia.
- Utilized serology (microimmunofluorescence) and PCR targeting specific Rickettsia genes (ompA, ompB, gltA) for detection and identification.
- Applied multispacer typing (MST) based on sequencing of three intergenic spacers (dksA-xerC, rmpE-tRNA(fMet), mppA-purC) for further characterization.
Main Results:
- Rickettsial infection confirmed in 60% of patients; Rickettsia DNA detected in 16% of skin biopsies, identifying R. conorii subsp. israelensis and R. conorii subsp. conorii.
- PCR on vectors revealed R. conorii subsp. israelensis (6/9 ticks), R. massiliae (2/9 ticks), R. conorii subsp. conorii (1/9 ticks), and R. felis (1/322 fleas).
- R. conorii subsp. israelensis and R. conorii subsp. conorii strains from humans and vectors exhibited new MST genotypes and demonstrated genetic homogeneity.
Conclusions:
- Novel genotypes of Rickettsia spotted fever group strains were identified in Tunisia.
- Genetic homogeneity among Rickettsia isolates from human and vector sources indicates epidemiologic circulation.
- The findings highlight the importance of molecular surveillance for understanding the transmission of re-emerging rickettsioses.
