Characterization of the new Chlamydia agent, TWAR, as a unique organism by restriction endonuclease analysis and DNA-DNA hybridization.

Several molecular techniques were used for comparison of the novel Chlamydia agent, TWAR, with Chlamydia trachomatis and Chlamydia psittaci. Unlike all serotypes of C. trachomatis and most strains of C. psittaci, the eight TWAR isolates examined did not contain extrachromosomal DNA. TWAR was readily distinguished from C. trachomatis or C. psittaci by restriction endonuclease analysis, whereas identical or nearly identical restriction patterns were observed among the TWAR isolates. Southern blot analysis with a gene encoding a portion of the C. trachomatis serovar L2 major outer membrane protein as the probe showed that TWAR, like C. psittaci, contained sequences homologous to this gene. However, while the hybridization patterns were identical for all TWAR isolates, they differed from those of any of the other Chlamydia species tested. A PstI gene bank containing TWAR DNA was constructed in pUC19. Random fragments were purified and used for probing Chlamydia chromosomal digests. All of the five probes tested were TWAR specific, with the TWAR isolates showing identical patterns of homology. Qualitative studies of the DNA homology revealed that TWAR did not have significant homology to any of the Chlamydia strains assayed. Collectively, these results demonstrate that the TWAR isolates represent a single strain or closely allied genotypes and are clearly distinct from any of the other chlamydiae tested.