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Protozoal Microorganisms as Intestinal Parasites 37

TABLE 3-1 Classification of Pathogenic and Nonpathogenic Protozoa

PHYLUM SUBPHYLUM ATTRIBUTES EXAMPLES OF SPECIES
Sarcomastigophora Sarcodina Single-celled Acanthamoeba sp.
(amoebae) Motility by pseudopodia Endolimax nana
Cysts and trophozoite forms Entamoeba coli
Asexual reproduction Entamoeba hartmanni
Entamoeba histolytica
Iodamoeba butschlii
Naegleria fowleri

Mastigophora Single-celled Chilomastix mesnili
(flagellates) Movement chiefly by flagella Dientamoeba fragilis
Cysts and trophozoites for intestinal Enteromonas hominis
organisms Giardia lamblia
Asexual reproduction Leishmania species
Blood flagellates may be included Trichomonas hominis
Trichomonas tenax
Trichomonas vaginalis
Trypanosoma species
Ciliophora Single-celled Balantidium coli
(ciliates) Movement chiefly by cilia
Cysts and trophozoites stages
Asexual reproduction
Apicomplexa Coccidia Single-celled Babesia microti
Inhabit host’s cells Cryptosporidium parvum
Life cycle complex and involves Cyclospora cayetanensis
insects, mammals other than host Isospora belli
Both sexual and asexual Plasmodium species
reproduction may be involved Pneumocystis carinii
(jirovecii)
Sarcocystis species
Toxoplasma gondii

CLASSIFICATION OF CILIATES are smaller, thinner, and more hairlike than the longer
flagella possessed by some species. These cilia may cover
A number of important parasites with which humans the entire periphery of the membrane of the organism as
become infected are found in the class formerly called in the case of B. coli.
Ciliata but now are classified as Ciliophora, a phylum
of the kingdom Protista; the term Ciliata is still widely
used. The phylum Ciliophora includes both unicellular BALANTIDIUM COLI
and multicellular (colonial, or colony-forming) organ-
isms that possess cilia for locomotion. Some are free- The organism called Balantidium coli is considered to
living forms found in the environment and some are be the only ciliate found in humans that is pathogenic and
parasitic species that will be discussed individually in the is also the largest protozoan parasite found in humans.
following sections of this book (Balantidium coli, found This organism is of the genus of ciliated protozoa that
next, is one prime example). The cilia these organisms may be found in a number of hosts generally responsible
use for locomotion are essentially a sort of flagella that for infecting humans.