ГЕНЕТИЧЕСКОЕ ТИПИРОВАНИЕ RICKETTSIA AKARI

Аннотация

Rickettsia akari, an obligately intracellular bacterium, is the causative agent of the cosmopolitan urban disease rickettsialpox. Rickettsia akari is an atypical representative of spotted fever group rickettsiae (SFG) as it is associated with rodent mites rather than ticks or fleas; however, only limited information is available about the degree of genetic variability found among isolates of R. akari. We examined 13 isolates of R. akari from humans, rodents and mites in the USA, the former Soviet Union, and the former Yugoslavia made between 1946 and 2003 for diversity in their tandem repeat regions and intergenic regions. The 1.23 Mb genome of R. akari strain Hartford CWPP was analyzed using Tandem Repeat Finder software (http://tandem.bu.edu) and 374 different TRs were identified, with size variation from 1 to 483 bp and with TR copy numbers ranging between 21 and 1.9, respectively. No size polymorphisms were detected among the 11 tandem repeat regions examined from 5 open reading frames and 6 intergenic region. Eighteen non-tandem repeat intergenic regions were amplified and sequenced for the same isolates comprising a total of 5,995 bp (0.49%) of the Hartford CWPP strain chromosome. Three single nucleotide polymorphism (SNP) sites were detected in two intergenic regions which permitted separation of the five R. akari isolates from Ukraine from the other eight isolates. In conclusion, this is the first study reporting genetic heterogeneity among R. akari isolates of different geographic origins and establishing a baseline of genetic diversity for this unique species of rickettsiae. Further exploration of this genetic diversity is needed to understand better the geographic distribution of R. akari and the epidemiology of rickettsialpox. The potential of mites as hosts for other rickettsial agents also needs further investigation, as well as it associations with various mammalian hosts and potential to cause severe disease in individuals of various demographics and immune status.