Comprehensive genome analysis and comparisons of the swine pathogen, Chlamydia suis reveals unique ORFs and candidate host-specificity factors.

Chlamydia suis, a ubiquitous swine pathogen, has the potential for zoonotic transmission to humans and often encodes for resistance to the primary treatment antibiotic, tetracycline. Because of this emerging threat, comparative genomics for swine isolate R19 with inter- and intra-species genomes was performed. A 1.094 Mb genome was determined through de novo assembly of Illumina high throughput sequencing reads. Annotation and subsystem analyses were conducted, revealing 986 putative genes (Chls_###) that are predominantly orthologs to other known Chlamydia genes. Subsequent comparative genomics revealed a high level of genomic synteny and overall sequence identity with other Chlamydia while 92 unique C. suis open reading frames were annotated. Direct comparison of Chlamydia-specific gene families that included the plasticity zone, inclusion membrane proteins, polymorphic membrane proteins and the major outer membrane protein, demonstrated high gene content identity with C. trachomatis and C. muridarum. These comparisons also identified diverse components that potentially could contribute to host-specificity. This study constitutes the first genome-wide comparative analysis for C. suis, generating a fully annotated reference genome. These studies will enable focused efforts on factors that provide key species specificity and adaptation to cognate hosts that are attributed to chlamydial infections, including humans.