Chlamydia pneumoniae, strain TWAR.

A new third species of Chiamydia, called C pneumoniae, has been established for the TWAR organism. We first thought that the new organism belonged to the C psittaci species because it was clearly not a C trachomatis.2’8 Subsequent studies showed that the organism was unique from both currently recognized species.8”#{176}”7”9 Justification for establishing a new species rests primarily on studies of the ultrastructure of the elementary body’#{176}and DNA analysis.”9 The organism also is serologically unique from the C trachomatis species and all C psittaci strains tested.2’8 Ultrastructural studies have shown that C pneumoniae has a pear-shaped elementary body. The cytoplasmic mass is round and there is a large penplasmic space . This is entirely different from the elementary bodies of C trachomatis and C psittaci that are round, dense, and have a narrow or barely discernible periplasmic space . Genetic analysis revealed 10 percent or less DNA relatedness between C pneumoniae and the other two species, while homology among the TWAR strains tested was 94 percent or The restriction endonuclease patterns were similar among C pneumoniae isolates and readily distinguishable from C trachomatis and C psittaci strains.” The C pneumoniae also can be differentiated from the other species by using cloned C pneumoniae restriction fragments or whole chromosomal DNA as probes.”