Cytological changes related to Brucella canis variants uptake in vitro.

In this study, evidence for in vitro uptake, invasion, and cytopathogonomic effects of normal and variant strains of B. canis on tissue culture, is presented. B. canis L-phase were penicillin-induced and these microorganisms produced revertants on penicillin-free media. Tissue culture (LLC-MK2) cells were divided into different normal and variant-infected groups (I-IV), including controls. Bright-field and electron microscopic observations indicated uptake of all the strains and recognizable host cell damage (CPE) to varying degrees. At 72 h after infection, the extent of damage by L-phase was the least (55.5% CPE). The L-phase-derived revertants resulted in 80% damage; this approximates the adverse effect of normal B. canis (85%). In addition to these gross changes, various structural abnormalities, including pyknosis, nuclear disorganization, vacuolation, and karyorrhexis, were apparent. The implications of these findings and the indirect role of the L-phase in brucellosis due to B. canis are discussed.