Jpn. J. Infect. Dis., 54, 75-76, 2001
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Laboratory and Epidemiology Communications
Detection of Anti-Coxiella burnetii Antibodies by Immunofluorescent Technique and Enzyme-Linked Immunosorbent Assay
Yumiko Furuya*, Takashi Katayama, Miyuki Hara, Yoshiya Yoshida, Mitsunobu Imai, Yasutomo Arashima1, Kimitoshi Kato1, Motohiko Ogawa2 and Toshikatu Hagiwara2
Kanagawa Prefectural Public Health Laboratory, Nakao 1-1-1, Asashi-ku, Yokohama, Kanagawa 241-0815, 1Nihon University School of Medicine, Oyaguchi-Kamimachi 30-1, Itabashi-ku, Tokyo 173-0032 and 2National Institute of Infectious Diseases, Toyama 1-23-1, Shinjuku-ku, Tokyo 162-8640
Communicated by Kunihiko Masukawa
(Accepted April 17, 2001)
Q fever is caused by a zoonotic pathogen, Coxiella burnetii. Infected humans exhibit influenza-like respiratory symptoms. The antibody-positive population is high among animal farm workers including veterinary doctors (1). It was suggested that some patients diagnosed as having atypical pneumonia or other respiratory infections actually have C. burnetii infections (2,3).
This report deals with the detection of anti-C. burnetii antibodies among 48 patients with respiratory infections. All the patients showed prolonged fever, cough and respiratory excretion with unknown etiology. Though anti-C. burnetii antibody is usually detected by means of the immunofluorescent antibody technique (IF) employing phase II antigen (4), this method requires expertise. Therefore, we performed the IF in combination with ELISA by using phase I and phase II antigens.
Positive control serum from a convalescent Q fever patient (5) showed a titer of ~512 in IF and ~16,000 in ELISA (6) for both phase I and II antigens. C. burnetii TK-1 strain was isolated from the patient.
Three among seven sera with IF titers ~16 were negative as determined by ELISA. However, among eight sera with IF titers higher than ~32, only one was negative (Table 1). IF titer ~16 or lower was probably due to non-specific reaction or to cross-reaction. Actually, it has been reported that Bartonella or Legionella antigens cross-reacted with C. burnetii antigen (7,8). Relatively higher titers, >~32, probably reflect specific reactions because the IF and ELISA data matched well.
Positivity tended to be higher for phase II antigen than for phase I antigen (data not shown).
ELISA-positive sera with IF titers higher than ~32 were seen in 7 of 48 (14.6%) respiratory infections (Table 1), while it was seen in 1 of 200 (0.5%) in a healthy population. The positive rate was about 30-fold higher in the respiratory infections. This may indicate the involvement of C. burnetii in respiratory infections. However, the involvement of other antigen-cross-reactive pathogens could not be excluded. Further studies with paired sera from more patients will be needed for elucidating the causal relation between C. burnetiii and chronic respiratory infections.
Phase I and Phase II C. burnetti (Nine Mile strain) were obtained from Dr. E. Kovacova, Czechoslovakia Academy of Science.
REFERENCES
*Corresponding author: Tel: +81-45-363-1030, Fax: +81-45-363-1037
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