ELECTRON-MICROSCOPY STUDY OF THE MODE OF GROWTH OF PSEUDOMONAS-PSEUDOMALLEI IN-VITRO AND IN-VIVO

The mode of growth of Pseudomonas pseudomallei in culture media and in the lung tissue of infected humans and animals was studied using tran smission electron microscopy (TEM) and scanning electron microscopy (S EM). In culture media, P. pseudomallei cells were seen to be entrapped in microcolonies within large amounts of intercellular fibrous materi al. The lung tissue of infected humans and animals showed that bacteri al cells growing in lung tissue were surrounded by radially arranged f ibres that constitute a very well defined glycocalyx structure. In the infected areas of the animal lung tissue, bacterial cell could be see n to have formed glycocalyx enclosed microcolonies that displaced host cell components, e.g. the nucleus of a phagocyte. The presence of bac teria in unusual locations indicated that effective phagocytosis was n ot occurring. The demonstration that cells of P. pseudomallei produce exopolysaccharide glycocalyces and form glycocalyx enclosed microcolon ies in laboratory media and in lung tissue of infected humans and anim als and the presence of bacteria in unusual locations contribute to a new understanding of the mechanism whereby this organism can cause per sistent chronic infections.