Virulence of Campylobacter jejuni for chicken embryos is associated with decreased bloodstream clearance and resistance to phagocytosis

Abstract

The 11-day-old chicken embryo has been shown to be a useful animal model for comparing the virulence of human isolates of Campylobacter jejuni. Virulence in this system is associated with the ability to invade the chorioallantoic membrane and to survive and proliferate in vivo. In this study, the survival and multiplication of C. jejuni in the embryonic host was investigated. It was possible to enhance the virulence of a relatively avirulent C. jejuni strain by passaging it intravenously through the embryos. The resulting isogenic variants demonstrated enhanced abilities to survive in vivo but were still unable to invade when inoculated onto the chorioallantoic membrane. The bloodstream clearance of C. jejuni was studied, and virulent, but not avirulent, strains persisted and multiplied both in the bloodstream and in embryonic liver. Virulent strains also were cleared significantly more slowly from the bloodstream of adult BALB/c mice after intravenous challenge than were avirulent strains. C. jejuni strains which were cleared slowly in vivo were also ingested slowly in vitro by mouse peritoneal macrophages. Clearance studies in mice pretreated with cobra venom factor demonstrated that opsonization by serum complement was not a prerequisite for clearance of campylobacters from the murine bloodstream.

Morphology heterogeneity within a Campylobacter jejuni helical population: the use of calcofluor white to generate rod‐shaped C. jejuni 81‐176 clones and the genetic determinants responsible for differences in morphology within 11168 strains

“…This population heterogeneity allows for rapid adaptation and survival under new conditions. The appearance of rod shaped variants, such as those arising from exposure to CFW described in this study, our laboratory 11168‐GS strain (Gaynor et al ., ), those generated by passage through chick embryos (Field et al ., ) and chickens (Hanel et al ., ), and those that appeared in some flagellar mutants (Wassenaar et al ., ; Matz et al ., ; Fernando et al ., ) that are unlinked to the flagellar mutation indicate that the ability of C. jejuni to alter its shape from helical to straight provides a selective advantage to C. jejuni under certain stress conditions. The exact nature of this stress remains to be determined.…”

“…There have been reports in the literature of straight C. jejuni strains arising from helical strains, although the basis of the altered morphology in these cases has yet to be established. Passage of an avirulent C. jejuni strain through chick embryos led to the isolation of more virulent rod‐shaped strains better able to resist phagocytosis and survive in vivo (Field et al ., ; ). In another study, various C. jejuni strains were used to colonize chickens and the strains were reexamined after passage through the chicken gut.…”

Pathogenesis of Enteric Infection by Campylobacter

“…Without opsonization, phagocytosis and killing is less efficient and strain-dependent (Pennie et al, 1986; Walan et al, 1992; Autenrieth et al ., 1995). In contrast to phagocytosis by PMNLs, opsonization by antibody or complement is not required for efficient uptake by macrophages (Field et al, 1991). C. jejuni can survive within macrophages for up to 6–7 d (Kiehlbauch et al, 1985) despite a complete conversion of intracellular bacteria to coccoid forms.…”

Expression of Invasiveness of Campylobacter jejuni ssp. jejuni after Serial Intraperitoneal Passages in Mice

“…Several animal models have been proposed to enhance the virulence of C. jejuni, increasing their colonization potential (Sang et al, 1989;Field et al, 1991;Saha et al, 1991;Cawthraw et al, 1996) and their resistance to phagocytosis and their survival ability in vivo (Field et al, 1991). A mouse i.p.…”

“…passage and inoculation of chick embryos enhance or restore the expression of virulence of different C. jejuni ssp. jejuni isolates (Kazmi et al, 1984;Field et al, 1991;Saha et al, 1991).…”