Investigation of an emergent, tetracycline-resistant, abortifacient Campylobacter jejuni clone in a pregnant guinea pig model

Campylobacter spp. have been recognized as an important cause of sheep abortion for decades; however, recent analyses have revealed that C. jejuni has replaced C. fetus subsp. fetus as the predominant species isolated, and that a single clone of tetracycline-resistant C. jejuni, named clone SA for Sheep Abortion, has emerged as the predominant isolate across multiple states and multiple lambing seasons. The emergence of this genetic clone reveals a dramatic shift in the epidemiology of ovine campylobacteriosis and warrants further investigation. Herein we describe oral inoculation of the pregnant guinea pig as an appropriate model to study the pathogenesis of septic abortion due to clone SA with 60% (6/10) of animals aborting within 21 days of inoculation with a clinical isolate (C. jejuni IA3902) of this highly pathogenic clone. In placentas obtained from these aborting guinea pigs, we observed significantly increased TLR2 protein in subplacental syncytiotrophoblast cells while TLR4 expression was relatively unchanged, suggesting a role for TLR2 in the pathogenesis of Campylobacter-associated abortion. We describe resolution of infection after intraperitoneal challenge in guinea pigs as a means to compare efficacy of two commercially available Campylobacter vaccines and an experimental bacterin. In this challenge study, one commercial vaccine was entirely ineffective and may suggest a means of positive selection for the emergence of clone SA. Lastly, we describe the spatial localization of mucin, iron and L-fucose within the guinea pig placental unit and compare the effects of these chemicals, placental tissue extracts, blood, and bile from pregnant guinea pigs on the growth and chemotaxis of C. jejuni. Our findings reveal the presence of growth promoting and chemoattractive substances for C. jejuni within the guinea pig placental unit and suggest a role for these factors in the fetoplacental tropism observed with this strain. The results of these studies provide insight into potential mechanisms underlying the pathogenesis of septic abortion following infection with clone SA of C. jejuni, and to the emergence of this highly pathogenic strain.