Growth, Morphogenesis, and Virulence of Candida albicans after Oral Inoculation in the Germ-Free and Conventional Chick

Abstract

, N.Y.), AND A. W. PHILLIPS. Growth, morphogenesis, and virulence of Candida albicans after oral inoculation in the germ-free and conventional chick. J. Bacteriol. 91:1736-1743. 1966.-The effects of intestinal bacteria on the multiplication, morphogenesis, and infectivity of Candida albicans in the alimentary tract were investigated by comparing results obtained in germ-free and conventional chicks after oral inoculation. This challenge resulted in the establishment of large numbers of the pathogen in the alimentary tract of each group of chicks; these numbers were increased in crop contents from challenged bacteria-free chicks wherein hyphae predominated over the yeast form. These animals also had lesions of the crop epithelium containing numerous hyphae and few yeastlike forms. In contrast, challenged conventional chicks receiving an adequate diet displayed no evidence of infection. Their alimentary tract contained the yeast form of C. albicans; no hyphae were seen. Although we found bacterial inhibition of C. albicans multiplication in the alimentary tract, this in itself did not seem to explain the resistance to intestinal candidiasis in our conventional chicks. We argued that this resistance to infection was due chiefly to the prevention of hyphal development in C. albicans by intestinal bacteria. C. albicans in the gut of our conventional chicks resulted in some increase in numbers of enterococci in contents from the crop. Increased pH values in contents from the gut of germ-free chicks were not clearly related to infection after challenge. The Eh of the above crop contents were only slightly decreased in the germ-free crop. Thus the Eh did not appear to be involved in susceptibility to infection. Invasion of the blood stream and kidneys of conventional chicks by the yeast form of C. albicans occurred in challenged animals receiving a purified diet which had been radiation-sterilized and stored for 6 months at room temperature (25 C). Their growth rate decreased and they became moribund; no hyphae were observed in tissues or intestine of these animals. Challenged bacteria-free chicks receiving the same diet were resistant to the above invasion, although they had crop lesions containing hyphae as described. The resistance of these chicks to systemic invasion was attributed to absence of intestinal bacteria competing for low levels of vitamins in the stored diet. Germ-free chicks had decreased levels of serum-y-globulin which increased after challenge, whereas this value was unchanged in conventional birds after challenge. The occurrence of Candida albicans as a tract (and other sites) in man and other animals commensal or as a pathogen in the alimentary was reported by many workers (31). Others 'Taken in part from a thesis submitted by the suggested that certain members of the intestinal senior author in partial fulfillment of the require-flora may hinder infection of a host by C. albicans. ments for the Ph.D. degree, Syracuse University, For example, chicks and turkey poults were Syracuse, N.Y. resistant to...

Influence of Antibiotics or Certain Intestinal Bacteria on Orally Administered Candida albicans in Germ-Free and Conventional Mice

“…In previous studies, C. albicans has been administered to germ-free mice and chickens. Balish and Phillips (2) have shown that oral challenge with C. albicans resulted in crop infections in all germ-free chicks, whereas conventional chicks were not infected. They concluded that the enteric microbial flora of the conventional chick provides protection against candidiasis.…”

Colonization of congenitally athymic, gnotobiotic mice by Candida albicans

“…Under natural conditions, neonates acquire C. albicans from their mothers early in life, and the yeast usually persists as a minor and innocuous component of the mucosal flora thereafter. Apparently, the normal bacterial flora inhibits the growth of C. albicans in the alimentary tract since oral therapy with antibacterial antibiotics often results in dramatic increases in the number of viable C. albicans on mucosal surfaces (1,7,10,32).…”

Differences in virulence of clinical isolates of Candida tropicalis and Candida albicans in mice

“…Because the oral cavity and GI tract are common sites of colonization in humans and recognized portals of entry for Candida (3, 7, 14-16), models in which the GI tract is employed as the route of fungal challenge have been developed (1,11,12,17,18). Since these organisms are ordinarily commensal and are opportunistic only when the host defenses are altered, our model host was given antibiotics and cytoreductive agents at doses and in a pattern that would simulate the setting in our human patient population.…”