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J Clin Microbiol. Nov 1993; 31(11): 2967–2973.
PMCID: PMC266174

Life cycle of the human and animal oomycete pathogen Pythium insidiosum.


Pythium insidiosum, the etiologic agent of pythiosis insidiosii, causes life-threatening infections in humans and animals. Previous studies of the epidemiology of this disease hypothesized about the possible life cycle of this oomycete. Details, however, were not provided on the steps required to cause infection. We investigated the life cycle of P. insidiosum by inoculating pieces of equine skin and plant leaves and then studying the ensuing events with a scanning electron microscope. Our observations revealed that zoospores had a strong tropism for skin tissue, horse and human hair, and water lily and grass leaves and a weak attraction to a variety of other leaves. Encysted zoospores were observed on the favored leaves and skin. There they produced germ tubes and later abundant hyphal filaments that penetrated leaf tissues. Young sporangia had compact, thick walls. The sporangial wall was reduced to a fragile membrane when the sporangia had produced well-differentiated biflagellate zoospores. The encysted zoospores secreted an amorphous material that permitted the zoospores to adhere to skin and plant tissues. On the basis of these findings, a model to explain the life cycle of P. insidiosum is proposed.

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  • Alfaro AA, Mendoza L. Four cases of equine bone lesions caused by Pythium insidiosum. Equine Vet J. 1990 Jul;22(4):295–297. [PubMed]
  • Austwick PK, Copland JW. Swamp cancer. Nature. 1974 Jul 5;250(461):84–84. [PubMed]
  • Brown CC, Roberts ED. Intestinal pythiosis in a horse. Aust Vet J. 1988 Mar;65(3):88–89. [PubMed]
  • Cameron JN, Carlile MJ. Binding of isovaleraldehyde, an attractant, to zoospores of the fungus Phytophthora palmivora in relation to zoospore chemotaxis. J Cell Sci. 1981 Jun;49:273–281. [PubMed]
  • Chaiprasert A, Samerpitak K, Wanachiwanawin W, Thasnakorn P. Induction of zoospore formation in Thai isolates of Pythium insidiosum. Mycoses. 1990 Jun;33(6):317–323. [PubMed]
  • De Cock AW, Mendoza L, Padhye AA, Ajello L, Kaufman L. Pythium insidiosum sp. nov., the etiologic agent of pythiosis. J Clin Microbiol. 1987 Feb;25(2):344–349. [PMC free article] [PubMed]
  • Goad ME. Pulmonary pythiosis in a horse. Vet Pathol. 1984 Mar;21(2):261–262. [PubMed]
  • Hamer JE, Howard RJ, Chumley FG, Valent B. A mechanism for surface attachment in spores of a plant pathogenic fungus. Science. 1988 Jan 15;239(4837):288–290. [PubMed]
  • Smith JL, Lane AC, Hodges E, Reynolds WM, Howell WM, Jones DB, Janson CH. T-cell receptor variable (V) gene usage by lymphoid populations in T-cell lymphoma. J Pathol. 1992 Feb;166(2):109–112. [PubMed]
  • Mazia D, Schatten G, Sale W. Adhesion of cells to surfaces coated with polylysine. Applications to electron microscopy. J Cell Biol. 1975 Jul;66(1):198–200. [PMC free article] [PubMed]
  • Mendoza L, Kaufman L, Standard P. Antigenic relationship between the animal and human pathogen Pythium insidiosum and nonpathogenic Pythium species. J Clin Microbiol. 1987 Nov;25(11):2159–2162. [PMC free article] [PubMed]
  • Mendoza L, Prendas J. A method to obtain rapid zoosporogenesis of Pythium insidiosum. Mycopathologia. 1988 Oct;104(1):59–62. [PubMed]
  • Miller RI. Investigations into the biology of three 'phycomycotic' agents pathogenic for horses in Australia. Mycopathologia. 1983 Jan 17;81(1):23–28. [PubMed]
  • Miller RI, Olcott BM, Archer M. Cutaneous pythiosis in beef calves. J Am Vet Med Assoc. 1985 May 1;186(9):984–986. [PubMed]
  • Sathapatayavongs B, Leelachaikul P, Prachaktam R, Atichartakarn V, Sriphojanart S, Trairatvorakul P, Jirasiritham S, Nontasut S, Eurvilaichit C, Flegel T. Human pythiosis associated with thalassemia hemoglobinopathy syndrome. J Infect Dis. 1989 Feb;159(2):274–280. [PubMed]

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