Human granulocytic anaplasmosis (HGA) is a tick borne infection
caused by Anaplasma phagocytophilum. HGA cases
in South Korea have been identified since the first report in
2014. In this study, we investigated the serological response
in 594 clinical samples of patients with acute febrile illness
and molecular characteristics of A. phagocytophilum clinical
isolates obtained from HGA patients. In serological test for
A. phagocytophilum, 7.91% (47/594 cases) were positive for
IgG and Ig M and 13 of 47 cases showed seroconversion. In
the detection rate of the 16S rRNA, msp2(p44), and ankA,
genes were showed 3.68% (14/380 cases) for A. phagocytophilum-
specific 16S rRNA gene. Phylogenetic analysis of three
clinical isolates demonstrated high sequence similarity (98.58–
100%) with A. phagocytophilum 16S rRNA sequences identified
from public databases. Analysis of the msp2(p44) gene
showed highly variable similarity rates (7.24–98.85%) even
within isolated countries and host ranges. These results provide
clues into the bacterial characterization of A. phagocytophilum
originating from Korean patients, providing useful
guidance for treatment and improving clinical outcomes.