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Chiyoung Park - One of the best experts on this subject based on the ideXlab platform.

Takanori Ueda - One of the best experts on this subject based on the ideXlab platform.

  • tsutsugamushi disease caused by shimokoshi type Orientia tsutsugamushi the first report in western japan
    American Journal of Tropical Medicine and Hygiene, 2013
    Co-Authors: Satoshi Ikegaya, Nobuhiro Takada, Seigo Yamamoto, Hiromichi Iwasaki, Takanori Ueda
    Abstract:

    An 85-year-old female farmer was admitted to our hospital for fever, general fatigue, and skin rash. Cephalosporin was not effective and minocycline was dramatically effective. An eschar was discovered on her inguinal region after the defervescence. Laboratory examination of serum taken 12 days after onset of the illness showed elevated titers of antibodies against the Shimokoshi strain of Orientia tsutsugamushi. The gene sequence analysis of specimen from the patient's eschar revealed high similarity to the Shimokoshi strain by nested polymerase chain reaction. Therefore, this patient was diagnosed as a case of Shimokoshi-type tsutsugamushi disease, which has not previously been reported in Western Japan. Recently, cases of this type have also been confirmed in northeastern Japan, suggesting the need for further epidemiological studies.

Dae Woong Kang - One of the best experts on this subject based on the ideXlab platform.

Jae Seung Kang - One of the best experts on this subject based on the ideXlab platform.

  • In Vitro Activity of Tigecycline Against Orientia tsutsugamushi
    Yonsei Medical Journal, 2016
    Co-Authors: Sun Myoung Lee, Jae Seung Kang, Hae Yoon Kwon, Ji Hyeon Baek, Seung Sik Hwang, Moon Hyun Chung, Jin Soo Lee
    Abstract:

    Scrub typhus is a zoonosis caused by Orientia tsutsugamushi (O. tsutsugamushi) occurring mainly in autumn in Korea. The need of new antibiotics has arisen with a report on strains resistant to antibiotics and chronic infection. This study aims to identify susceptibility of tigecycline in-vitro as a new therapeutic option for O. tsutsugamushi. Antibacterial activity of tigecycline against the O. tsutsugamushi was compared with doxycycline using flow cytometry assay. The inhibitory concentration 50 (IC₅₀) was 3.59×10⁻³ μg/mL in doxycycline-treated group. Whereas in 0.71×10⁻³ μg/mL tigecycline-treated group. These findings indicate that tigecycline may be a therapeutic option for the treatment of scrub typhus.

  • Identification of Outer Membrane Vesicles Derived from Orientia tsutsugamushi
    Journal of Korean Medical Science, 2015
    Co-Authors: Sun Myoung Lee, Jae Seung Kang, Ji Hyeon Baek, Hea Yoon Kwon, Jin Soo Lee
    Abstract:

    Orientia tsutsugamushi, a causative pathogen of Scrub typhus, is a gram-negative intracellular bacterium. Outer membrane vesicles (OMVs) are produced from the membrane of bacteria and play many roles related to the survival of the pathogen. However, there have been no reports confirming whether O. tsutsugamushi indeed produce OMVs. O. tsutsugamushi boryong was cultured in ECV-304 cells for the purification of OMVs. Western blot analysis and immunoenrichment using anti-O. tsutsugamushi monoclonal antibody and electron microscopy were employed for identification and characterization of OMVs. We confirm the presence of OMVs derived from O. tsutsugamushi, and also found that those OMVs contain a major surface antigen of 56-kDa protein and variant immunogenic antigens.

  • In Vitro Bacteriostatic Effects of Rifampin on Orientia tsutsugamushi
    Journal of Korean Medical Science, 2014
    Co-Authors: Ji Hyeon Baek, Sun Myoung Lee, Moon Hyun Chung, Jin Soo Lee, Jae Seung Kang
    Abstract:

    We performed an in vitro cell culture experiment to ascertain whether rifampin exhibits bactericidal effects against Orientia tsutsugamushi, the causative agent of scrub typhus. ECV304 cells were infected with the Boryong or AFSC-4 strain of O. tsutsugamushi and then, the cultures were maintained in media with increasing concentrations of rifampin, azithromycin, doxycycline, or chloramphenicol for 4 days. On day 5, the media were replaced with fresh antibiotic-free medium and the cultures were maintained until day 28. On days 5, 13, and 28, immunofluorescence (IF) staining of O. tsutsugamushi was performed. IF staining on days 13 and 28 revealed increasing numbers of IF-positive foci in all cultures, even in cultures initially exposed to the highest concentration of rifampin (80 µg/mL), azithromycin (80 µg/mL), doxycycline (20 µg/mL), or chloramphenicol (100 µg/mL). The present study reveals that rifampin has no bactericidal effect against O. tsutsugamushi as observed for azithromycin, doxycycline, and chloramphenicol. A subpopulation of the bacteria that are not killed by high concentrations of the antibiotics may explain the persistence of O. tsutsugamushi in humans even after complete recovery from scrub typhus with antibiotic therapy. Graphical Abstract Keywords: Antibiotic Susceptibility Test, Azithromycin, Drug Resistance, Bacterial, Orientia tsutsugamushi, Rifampin, Scrub Typhus INTRODUCTION Scrub typhus is an easily treatable illness if antibiotics such as chloramphenicol, doxycycline, azithromycin, or rifampin are used properly in therapy. Relapse occurs several days after discontinuation of antibiotic therapy in certain patients, when the antibiotic treatment was initiated early in the course of the illness, and in those with short treatment duration (1-3). The reason of such a relapse is that Orientia tsutsugamushi, the causative agent of scrub typhus, persists in human body after recovery from scrub typhus (4), while chloramphenicol or tetracycline has only bacteriostatic effects, as documented in mice (3,5). In contrast to chloramphenicol and tetracycline, rifampin sometimes exhibits bactericidal effects on certain bacteria (6), and no relapse was observed in a clinical trial employing rifampin (7). Thus, rifampin may possess bactericidal effects against O. tsutsugamushi. In addition, in northern Thailand, where doxycycline-insensitive strains prevail, rifampin showed a more rapid response against scrub typhus (8). There are several in vitro studies on antibiotic susceptibility against O. tsutsugamushi (9-12). However, these studies revealed only minimal inhibitory concentrations, and none of the studies evaluated the bactericidal effects of these antibiotics. Antibiotics with bactericidal properties against O. tsutsugamushi will prevent its persistence, and therefore, they may be used preferentially for the treatment of scrub typhus patients. Although macrolide antibiotics such as azithromycin exert bacteriostatic effects on conventional bacteria, there are no studies on the bacteriostatic effects of azithromycin against O. tsutsugamushi. In the present study, we performed an in vitro cell culture experiment to measure whether rifampin has bactericidal effects against O. tsutsugamushi. In addition, we assessed the bacteriostatic effects of azithromycin against O. tsutsugamushi.

  • High In Vitro Infectivity of a Doxycycline-Insensitive Strain of Orientia tsutsugamushi
    Infection & Chemotherapy, 2013
    Co-Authors: Min Su Kim, Sun Myoung Lee, Ji Hyeon Baek, Moon Hyun Chung, Jin Soo Lee, Jae Seung Kang
    Abstract:

    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.

  • Persistence of Orientia tsutsugamushi in Humans
    Journal of Korean Medical Science, 2012
    Co-Authors: Moon Hyun Chung, Ji Hyeon Baek, Jin Soo Lee, Mi-jeong Kim, Jae Seung Kang
    Abstract:

    We investigated the persistence of viable Orientia tsutsugamushi in patients who had recovered from scrub typhus. Blood specimens were available from six patients with scrub typhus who were at 1 to 18 months after the onset of the illness. The EDTA-treated blood specimens were inoculated into ECV304 cells, and cultures were maintained for 7 months. Sequencing of the 56-kDa type-specific antigen gene of O. tsutsugamushi was performed to ascertain the homology of isolates. O. tsutsugamushi was isolated from all six patients, and nucleotide sequences of isolates serially collected from each patient were identical in all five patients in whom nucleotide sequences were compared. One patient relapsed 2 days after completion of antibiotic therapy; two patients complained of weakness for 1 to 2.5 months after the illness; one patient underwent coronary angioplasty 6 months later; and one patient suffered from a transient ischemic attack 8 months later. This finding suggests that O. tsutsugamushi causes chronic latent infection, which may be associated with certain clinical illnesses, preceded by scrub typhus. Antibiotic therapy abates the symptoms of scrub typhus, but does not eradicate O. tsutsugamushi from the human body.

Seigo Yamamoto - One of the best experts on this subject based on the ideXlab platform.

  • tsutsugamushi disease caused by shimokoshi type Orientia tsutsugamushi the first report in western japan
    American Journal of Tropical Medicine and Hygiene, 2013
    Co-Authors: Satoshi Ikegaya, Nobuhiro Takada, Seigo Yamamoto, Hiromichi Iwasaki, Takanori Ueda
    Abstract:

    An 85-year-old female farmer was admitted to our hospital for fever, general fatigue, and skin rash. Cephalosporin was not effective and minocycline was dramatically effective. An eschar was discovered on her inguinal region after the defervescence. Laboratory examination of serum taken 12 days after onset of the illness showed elevated titers of antibodies against the Shimokoshi strain of Orientia tsutsugamushi. The gene sequence analysis of specimen from the patient's eschar revealed high similarity to the Shimokoshi strain by nested polymerase chain reaction. Therefore, this patient was diagnosed as a case of Shimokoshi-type tsutsugamushi disease, which has not previously been reported in Western Japan. Recently, cases of this type have also been confirmed in northeastern Japan, suggesting the need for further epidemiological studies.

  • genome comparison and phylogenetic analysis of Orientia tsutsugamushi strains
    DNA Research, 2010
    Co-Authors: Keisuke Nakayama, Hiroshi Urakami, Ken Kurokawa, Masahiro Fukuhara, Seigo Yamamoto, Kazuko Yamazaki, Yoshitoshi Ogura, Tadasuke Ooka, Tetsuya Hayashi
    Abstract:

    Orientia tsutsugamushi (OT) is an obligate intracellular bacterium belonging to the family Rickettsiaceae and is the causative agent of scrub typhus, or tsutsugamushi disease. The complete genome sequences of two OT strains (Boryong and Ikeda) have recently been determined. In the present study, we performed a fine genome sequence comparison of these strains. Our results indicate that although the core gene set of the family Rickettsiaceae is highly conserved between the two strains, a common set of repetitive sequences have been explosively amplified in both genomes. These amplified repetitive sequences have induced extensive genome shuffling and duplications and deletions of many genes. On the basis of the results of the genome sequence comparison, we selected 11 housekeeping genes and carried out multilocus sequence analysis of OT strains using the nucleotide sequences of these genes. This analysis revealed for the first time the phylogenetic relationships of representative OT strains. Furthermore, the results suggest the presence of an OT lineage with higher potential for virulence, which may explain the clinical and epidemiological differences between ‘classic’ and ‘new’ types of tsutsugamushi disease in Japan.