Conjunctivitis caused by a swine Chlamydia trachomatis-like organism in gnotobiotic pigs

The objective of this study was to determine whether a chlamydial strain re covered from growing and finishing swine with conjunctivitis or keratoconju nctivitis could cause the same infections in gnotobiotic pigs. The strain s hares biological characteristics with Chlamydia trachomatis. After propagat ion in Vero cells and preparation of the inoculum (10(7) inclusion-forming units/ml), chlamydial strain H7 was instilled into the ventral conjunctival sac (0.15 ml/sac) of 12 anesthetized 3-day-old gnotobiotic piglets. Four a ge-matched gnotobiotic piglets were anesthetized and sham infected with uni nfected cell culture lysates. None of the principal piglets developed clini cal symptoms of conjunctivitis or keratoconjunctivitis. Principal piglets n ecropsied 7 days postinfection (DPI) had histologic lesions of mild or mode rate conjunctivitis; immunohistochemical evaluation revealed chlamydial ant igen in conjunctival epithelium. A majority of principal piglets necropsied at 14-28 DPI had histologic lesions of mild conjunctivitis, but chlamydial antigen was not detected by immunohistochemistry. The results indicated th at chlamydial strain H7 can cause mild or occasionally moderate conjunctivi tis in gnotobiotic pigs, but the conjunctival infection is asymptomatic.