High In Vitro Infectivity of a Doxycycline-Insensitive Strain of Orientia tsutsugamushi.
We compared the infectivity and growth rates of 12 strains of Orientia tsutsugamushi in a cell culture system. ECV304 cells were infected with O. tsutsugamushi strains for 4 hr, and the culture was maintained for 72 hr. Immunofluorescence (IF) staining was performed at 4, 24, 48, and 72 hr after inoculation (hpi), and IF-positive foci were enumerated. The AFSC-4 strain, which is known to be insensitive to doxycycline, showed higher numbers of IF-positive foci than the other 11 strains at 4, 24, 48, and 72 hpi, which may explain its apparent insensitivity to antibiotics.
Department of Internal Medicine, Inha University School of Medicine, Incheon, Korea.
Min Su
MS
Kim
Department of Internal Medicine, Inha University School of Medicine, Incheon, Korea.
Ji Hyeon
JH
Baek
Department of Internal Medicine, Inha University School of Medicine, Incheon, Korea.
Jin-Soo
JS
Lee
Department of Internal Medicine, Inha University School of Medicine, Incheon, Korea.
Moon-Hyun
MH
Chung
Translation Research Center, Inha University School of Medicine, Incheon, Korea.
Sun Myoung
SM
Lee
Department of Microbiology, Inha University School of Medicine, Incheon, Korea.
Jae-Seung
JS
Kang
Drug resistance; Orientia tsutsugamushi; Scrub typhus; Virulence