Chlamydia suis displays high transformation capacity with complete cloning vector integration into the chromosomal rrn-nqrF plasticity zone.

The obligate intracellular Chlamydia genus contains many pathogens with a negative impact on global health and economy. Despite recent progress, there is still a lack of genetic tools limiting our understanding of these complex bacteria. This study provides new insights into genetic manipulation of Chlamydia with the opportunistic porcine pathogen Chlamydia suis, the only chlamydial species naturally harboring an antibiotic resistance gene, originally obtained by horizontal gene transfer. C. suis is transmissible to humans, posing a potential public health concern. We report that C. suis can take up vectors that lack the native plasmid, a requirement for most chlamydial transformation systems described to date. Additionally, we show that C. trachomatis, the most common cause for bacterial sexually transmitted infections and infectious blindness worldwide, can be transformed with C. suis vectors. Finally, the chromosomal region that harbors the resistance gene of C. suis is highly susceptible to complete vector integration.