Comparison of the nucleotide sequences of 16S rRNA, 444 Ep-ank, and groESLheat shock operon genes in naturally occurring Ehrlichia equi and human granulocytic Ehrlichiosis agent isolates from northern California

We examined 11 naturally occurring isolates of Ehrlichia equi in horses and two human granulocytic ehrlichiosis agent isolates in California for seque nce diversity in three genes. Ehrlichia equi isolates were from Sierra (n = 6), Mendocino (n = 3), Sonoma (n = 1), and Marin (n = 1) counties, and hum an granulocytic ehrlichiosis (HGE) agent isolates were obtained from Humbol dt county. PCR with specific primers for 16S rRNA, 444 Ep-ank and groESL he at shock operon genes successfully produced amplicons for all 13 clinical s amples. The 444 Ep-ank gene of the HGE agent and E, equi isolates from nort hern California is different from the eastern U.S. isolates BDS and USG3, T he translated amino acid sequence of the groESL heat shock operon gene frag ment is identical among E, equi, the HGE agent, and E, phagocytophila, with the exception of the northern Californian equine CASOLJ isolate. Microhete rogeneity was observed in the 16S rRNA gene sequences of HGE agent and E. e qui isolates from northern California. These results suggest that E. equi a nd the HGE agent found in California are similar or identical but may diffe r from the isolates of equine and human origin found in the eastern United States.