Submitted to: American Association of Veterinary Laboratory Diagnosticians
Publication Type: Abstract Only
Publication Acceptance Date: 6/28/1996
Publication Date: N/A
Technical Abstract: The genus Chlamydia includes over 60 strains that infect birds and/or animals including humans. The strains are currently grouped in 4 species (C. trachomatis, C. psittaci, C. pneumoniae, and C. pecorum). Using MAbs, PCR, PCR-RFLP, and DNA sequencing of MOMP and 16S-23S rDNA genes, we have been able to group chlamydial strains into 9 distinct groups. The chlamydial groups correlate with our prior understanding of host range, diseases produced, and virulence. This regrouping creates 3 subgroups in C. trachomatis (human, mouse, and swine) and 4 subgroups in C. psittaci (abortion, Guinea pig, feline, and avian). C. pecorum and C. pneumoniae species are unchanged. The identification of the chlamydial group is important, as each group has specific properties which affect isolation procedures, growth requirements, specimens needed for diagnosis, host range, and control procedures. The C. psittaci-abortion, C. psittaci- feline, and C. psittaci-Guinea pig groups have single serotypes that are quite stable worldwide. The groups such as C. pecorum and C. psittaci- avian each have a number of serovars and a wide host range; however, the individual serovars or strains appear to have narrow host ranges. In contrast, the groups C. trachomatis-human and C. trachomatis-swine have multiple serovars, but their host ranges are limited to humans and swine, respectively. Each group has different requirements for isolation and growth. The C. psittaci-abortion and C. psittaci-avian strains will grow in most cell cultures; however, the C. psittaci-feline and C. pecorum groups are much more difficult to grow, and embryonated eggs or McCoy cells are usually used. As more is learned about other growth requirements of the chlamydial groups, improvements will be made in diagnosis and control.