engleski

The ompA gene sequence of Rickettsia felis-like bacteria isolated from Haemaphysalis sulcata ticks

Haemaphysalis sulcata ticks, collected in southern Croatia, were recently found to be infected with Rickettsia felis-like bacteria. Based on the molecular and phylogenetic analysis of the complete gltA, partial 17 kDa and ompB gene sequences, the new rickettsial candidate clustered together with R. felis within SFG. Using the primers for the amplification of rickettsial ompA gene, we were unable to amplify this gene sequence. Even with newly described primers specific for R. felis ompA gene, no amplicons were obtained. Southern Croatia is an endemic region for Mediteranean spotted fever which symptoms resemble those of R. felis infection. Hence, the new R. felis-like bacteria from ticks needs to be further characterized to establish its pathogenic potential. Several discrepancies have been observed regarding the taxonomic position of R. felis. Furthermore, the typical SFG OmpA protein is supposed to be nonfunctional in R. felis and is considered as a dying gene. Immunodominant surface OmpA protein is used for diagnosis of rickettsioses, strain and species characterization and it is functionally involved in the pathogenesis of SFG rickettsiae. Therefore, the aim of here presented study was to amplify the complete ompA gene sequence of new R. felis-like bacteriaum from H. sulcata ticks. Since amplification of the required gene sequence was unsuccessful with the described primers, we designed several new primer sets based on the alignment of deposited rickettsial ompA sequences. Only one primer set produced an amplicon of 600 bp from 5` end of the gene. The genome walk was used to obtain the additional 3000 bp long gene sequence. Phylogenetic analysis of 3600 bp fragment of ompA revealed that R. felis-like bacteriaum from H. sulcata ticks clusters between R. felis and Rickettsia IRS4 and it most likely represents a new SFG rickettsia. However, the complete ompA sequence still needs to be assessed.

ompA gene; Rickettsia; Haemaphysalis sulcata

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