Ultrastructural Evidence for the Presence of Bacteria, Viral‐like Particles, and Mycoplasma‐like Organisms Associated with Giardia spp.¹

Abstract

Giardia trophozoites and cysts, isolated from mammalian and avian hosts, were examined by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and by fluorescent light microscopy for the presence of microbial symbionts. Mycoplasma-like organisms were observed on the surfaces of trophozoites isolated from the prairie vole, laboratory rat, and beaver. Intracellular bacteria were observed by TEM in the trophozoites and cysts of G. microti and by fluorescence microscopy in trophozoites and cysts of Giardia spp. isolated from beaver, muskrat, great-blue heron, and the green heron. Trophozoites of G. muris from rat small intestine contained viral-like particles measuring 60 nm in diameter. These observations suggest that biological associations between Giardia spp. and diverse microbes may be more common than formerly appreciated. It also raises the possibility of transmission of these apparent symbionts, via the Giardia cyst, to other mammalian hosts including man.

Jejunal Brush Border Microvillous Alterations inGiardia muris-Infected Mice: Role of T Lymphocytes and Interleukin-6

“…While the use of these models has significantly improved our understanding of the pathobiology of this parasite, the possibility of concurrent infections induced by inocula containing contaminated cysts has raised concerns in the recent scientific literature. Indeed, the presence of bacterial endosymbionts has been reported in Giardia cysts (21,41) and these organisms may have Shigella-like characteristics. In addition, other observations have revealed that viral endosymbionts can be found within Giardia trophozoites (21).…”

“…Indeed, the presence of bacterial endosymbionts has been reported in Giardia cysts (21,41) and these organisms may have Shigella-like characteristics. In addition, other observations have revealed that viral endosymbionts can be found within Giardia trophozoites (21). Therefore, in order to be able to attribute immunopathological factors to Giardia alone, and in an attempt to determine whether T lymphocytes are implicated in the pathogenesis of epithelial brush border injury during giardiasis, a new model, using an inoculum containing axenic (i.e., devoid of contaminating microorganisms) G. muris trophozoites, was developed and the absence of concurrent bacterial or viral inoculation was verified.…”

Survival of coliforms and bacterial pathogens within protozoa during chlorination

“…In this study, Citrobacter freundii, E. agglomerans, and K. pneumoniae were significantly more resistant to free chlorine residuals when ingested by amoebae ( Table 2). Feely et al (18) demonstrated that Giardia microti cysts contained intracellular bacteria, and DeJonckheere and Vande Voorde (14) showed that an Acanthamoeba sp. could survive chlorine exposure through the production of cysts.…”

Biology and Diseases of Rats

“…are ancient, with one of the most highly conserved genomes of all eukaryotes (Yu et al, 1996(Yu et al, , 1998. Giardia also has its own microflora, including mycoplasma-like particles and bacteria (Feely et al, 1988) and viruses (Tai et al, 1991(Tai et al, , 1996. Giardia muris colonizes a wide variety of mammalian hosts, including rats, mice, hamsters, and humans (Levine, 1961).…”