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ARS Home » Research » Publications at this Location » Publication #74235
Title: SYSTEMATIC CLASSIFICATION OF 41 STRAINS OF CHLAMYDIA USING THE RIBOSOMAL INTERGENIC SPACER AND DOMAIN I OF THE 23S GENE

Author
item Everett, Karin
item ANDERSEN, ARTHUR

Submitted to: International Journal of Systematic and Evolutionary Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/17/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: Chlamydia is a bacterial pathogen that grows inside cells. It causes abortion and reproductive disease, pneumonia, coronary artery disease, conjunctivitis, blindness, arthritis, enteritis, and encephalitis in humans and/or in livestock. Chlamydia's importance and role in producing these diseases have been difficult to document. For the most part, Chlamydia are restricted to growth in certain host species, and embryonated eggs and tissue culture systems must be used for cultivation in the laboratory. Strains that cause disease in livestock often cannot be cultivated at all. Recognition of chlamydial infection has been based on serology, electron microscopy, complement fixation, and micro- immunofluorescence of laboratory-grown field specimens. These techniques can be imprecise or difficult to perform. The findings of this research showed that Chlamydia can be easily and reliably identified and differentiated using a polymerase chain reaction to identify a portion of the Chlamydia ribosomal genes involved in protein manufacture. These genes showed similarities that clustered the various chlamydia into two branches with nine groups. The C. trachomatis branch contained groups specific for humans, swine, and rodents. The non-C. trachomatis branch contained six groups (C. pecorum, C. pneumoniae, and C. psittaci-abortion, -avian, -feline, and -guinea pig). Each group is associated with unique and specific health risks. This research will benefit the livestock industry by providing new, better, and relatively inexpensive tests for the identification of Chlamydia in diseased animals. These tests will help to determine the epidemiology of chlamydia so that the diseases it causes can be reduced and controlled.

Technical Abstract: Current methods used to classify Chlamydiae are imprecise or difficult to perform. To make it possible to identify and classify chlamydia, a 2.8 kb ribosomal DNA segment from a C. trachomatis strain and a C. psittaci strain was amplified by PCR and sequenced. Subsequently, 1320 bp of rDNA including both the 16S/23S intergenic spacer (232 b 11 bp) and Domain I (620 b 2 bp) of the 23S gene were selected and sequenced from each of 39 additional strains of chlamydia and from a chlamydia-like organism. Using parsimony analysis and also percent distance analysis, these sequences were found to have variable regions that grouped the isolates into two lineages (C. trachomatis and non-C. trachomatis) with nine distinct groups. Divergence of the two lineages, as measured by sequence differences, was comparatively large for both the intergenic spacer (18-24% difference vs. 13.9% for the next-largest group difference) and for Domain I (15-18% difference vs. 8.8%), demonstrating an early ancestral division between C. trachomatis strains and all other chlamydia strains. The C. trachomatis lineage included three genotypically-specific groups (human, swine, and mouse/hamster), and the non-C. trachomatis lineage included six genotypically-specific groups (C. pecorum, C. pneumoniae, and C. psittaci- abortion, -avian, - feline, and -guinea pig). These groups were congruent with host specificity, tissue specificity, and/or with disease produced. Phylogenetic trees based on these data were congruent with trees previously derived from MOMP gene sequences and DNA homology studies. DNA sequence analysis of either the intergenic spacer or Domain I provides a rapid and reproducible method for identifying and classifying chlamydial strains.