Submitted to: International Meeting of the European Society for Chlamydia Research
Publication Type: Proceedings
Publication Acceptance Date: 6/25/1996
Publication Date: N/A
Technical Abstract: Chlamydiae are classified at the species level using biological, morphological, and DNA hybridization techniques, and MOMP gene sequence analysis. These techniques can be imprecise or difficult to perform. In attempting to locate a conserved DNA sequence for detection of chlamydiae, a 2.8 kb ribosomal DNA segment of each of 41 isolates of chlamydiae was PCR Ramplified and over 1300 bp of each were subjected to double-stranded DNA sequence analysis. It was found that the ribosomal intergenic spacer and Domain I of the 23S gene both had variable regions that grouped the isolates. All strains of C. pneumoniae and C. pecorum were highly conserved, while strains of C. psittaci and C. trachomatis had considerably more variation. When isolates were regrouped into three trachomatis subgroups (human, swine, and mouse/hamster) and four psittaci subgroups (GPIC, FP, abortion, and avian) the differences were reduced (Table below). .The largest sequence differences were between C. trachomatis and all other types of chlamydia (average pair-wise differences for the intergenic spacer were 21.73% +/- 3.19, and for Domain I were 16.8% +/- 1.63). The differences among the non-trachomatis species were more restricted. A typical phylogenetic tree based on a single representative strain for each group and rooted to two known relatives of chlamydia appears below. Phylogenetic trees for Domain I (620 +/- 2 bp) and for the intergenic spacer (232 +/- 11 bp) were essentially identical and were congruent with trees previously derived from MOMP gene sequences (1100 bp) and from DNA homology studies. This analysis demonstrated that chlamydiae fall into nine groups, with the major need for subgrouping being in C. trachomatis and C. psittaci, as shown in the table and in the phylogenetic plot.