History of Chlamydia pneumoniae (TWAR)

Abstract

The history of the TWAR organism, now called Chlamydia pneumoniae, began in Taiwan in 1965. A field trial was under way testing an inactivated yolk sac-grown trachoma vaccine [1]. The trial was carried out in children, the endpoint being reduction in the incidence of clinical trachoma. At that time there was no adequate method to measure antibody response, and the organisms could be isolated only in the yolk sac of the embryonated egg. The children were followed by means of periodic isolation attempts from conjunctival swabs. A swab collected on 20 November 1965 from a child with the clinical diagnosis of trachoma dubium was frozen until 15 February 1966 and then inoculated in the yolk sac of embryonated eggs. This isolation attempt was the 2715th in our laboratories at the U.S. Medical Research Unit, No. 2, in Taipei. Dr. Russell Alexander was in charge of the laboratory at the time of these isolation attempts. In the first passage all eggs survived for 13 days and no elementary bodies were demonstrated on Macchiavello’s stain of yolk sac smears. A second blind passage was routinely made, and in the yolk sac of these eggs, typical elementary bodies of Chlamydia were demonstrated. The isolate was named TW-183, because it was the 183rd isolate in the laboratory. It was assumed that the isolate was a Chlamydia trachomatis strain.