Whole genome comparison between Erhlichia chaffeensis strains

Ehrlichia chaffeensis is an obligatory intracellular organism, and causes human monocytic ehrlichiosis (HME), a tick-borne illness. Clinical signs of HME vary from　asymptomatic infection to severe mobility that requires hospitalization or death. After whole genome sequencing of this bacterium, 425 open reading frames (38%) of 1115 in the genome were found as hypothetical gene with unknown function. A little is known about pathogenicity gene(s) and strain variation of this bacterium to date. Previously several E. chaffeensis strains were shown to be different based on comparison of limited gene sequences (p120, OMP-1[p28]s, and VLPT). To elucidate strain genetic variations and associated virulency, we carried out comparative genome hybridization (CGH) of E. chaffeensis Arkansas, Wakulla and Liberty strains, since these strains are most distinct in the previous studies. The tiling array containing approximately 300,000 probes of 29 nt spaced as dense as 8 bp on both strands of the genome of E. chaffeensis Arkansas was used. Keywords: Comparative genome hybridization Two samples were examined.