Chapter 21 : Intestinal Protozoa: Amebae

Life cycle of Entamoeba histolytica. doi:10.1128/9781555819002.ch21.f1

( 1 ) Trophozoite of Entamoeba histolytica; ( 2 ) trophozoite of E. histolytica/E. dispar/E. moshkovskii; (3 and 4) early cysts of E. histolytica/E. dispar/E. moshkovskii; (5 to 7) cysts of E. histolytica/E. dispar/E. moshkovskii; (8 and 9) trophozoites of Entamoeba coli; (10 and 11) early cysts of E. coli; (12 to 14) cysts of E. coli; (15 and 16) trophozoites of Entamoeba hartmanni; (17 and 18) cysts of E. hartmanni. doi:10.1128/9781555819002.ch21.f2

(a) Trophozoite of Entamoeba histolytica. (b) Trophozoite of Entamoeba histolytica/E. dispar/E. moshkovskii. (c and d) Cysts of E. histolytica/E. dispar/E. moshkovskii/E. bangladeshi (d is a precyst with a single nucleus). (e and f) Trophozoites of Entamoeba coli. (g to i) Cysts of E. coli (g is a precyst with two nuclei). Note the chromatoidal bars in panel h and the shrunken cyst (which is often seen in permanent stained smears) in panel i. Panel j represents an artifact that mimics an E. coli cyst (permanent stain). (Panel g is courtesy of the CDC Public Health Image Library.) doi:10.1128/9781555819002.ch21.f3

Amebic intestinal abscess. Note the “flask” shape (small opening on the mucosal surface and a larger area of destruction below the surface). (Courtesy of the CDC Public Health Image Library; Mae Melvin.) doi:10.1128/9781555819002.ch21.f4

Liver containing multiple amebic abscesses. The necrotic tissue has been removed from one portion, leaving a cavity. Magnification, ×0.4. (Armed Forces Institute of Pathology photograph.) doi:10.1128/9781555819002.ch21.f5

Amebic liver abscess. (Both images courtesy of the CDC Public Health Image Library.) doi:10.1128/9781555819002.ch21.f6

Intestinal amebiasis. Fecal immunoassay kits can be used on human stool specimens to identify organisms in the group E. histolytica/E. dispar or to differentiate E. histolytica from E. dispar. Currently available reagents require fresh or frozen specimens only. *, trophozoites containing RBCs confirmatory for E. histolytica; trophozoites with no ingested RBCs and/or cysts confirm only the E. histolytica/E. dispar group. doi:10.1128/9781555819002.ch21.Alg21.1

Amebic liver abscess. *, trophozoites containing RBCs confirmatory for E. histolytica; trophozoites with no ingested RBCs and/or cysts confirm only the E. histolytica/E. dispar group. doi:10.1128/9781555819002.ch21.Alg21.2

Life cycle of Entamoeba dispar, the same as E. moshkovskii and E. bangladeshi. doi:10.1128/9781555819002.ch21.f7

Life cycle of Entamoeba hartmanni, Entamoeba coli, Entamoeba polecki, Endolimax nana, and Iodamoeba bütschlii. doi:10.1128/9781555819002.ch21.f8

(Upper) Trophozoites of Entamoeba hartmanni; (lower) cysts of E. hartmanni. (Note that cysts often contain only two nuclei, instead of the mature four nuclei.) doi:10.1128/9781555819002.ch21.f9

(Upper, left) Cyst of Entamoeba polecki (illustration) (note the large inclusion in the cytoplasm as seen in the drawing); (right) cyst of E. polecki (direct wet mount with iodine; large vacuole is more difficult to see; however, chromatoidal bars are present). (Lower, left and right) E. polecki cyst forms (the large inclusion is visible in both organisms). doi:10.1128/9781555819002.ch21.f10

(Upper) Trophozoite of Entamoeba gingivalis (illustration by Sharon Belkin). (Lower, left and right) Trophozoites of E. gingivalis (note the ingested polymorphonuclear leukocytes—arrows). Both stained with iron-hematoxylin. doi:10.1128/9781555819002.ch21.f11

(1 to 5) Trophozoites of Endolimax nana; (6 to 10) cysts of E. nana; (11 to 13) trophozoites of Iodamoeba bütschlii; (14 to 16) cysts of I. bütschlii. doi:10.1128/9781555819002.ch21.f12

(Upper, left and right) Trophozoites of Endolimax nana (note the nuclear variation in both organisms). (Lower) Cysts of E. nana, containing four karyosomes with no peripheral chromatin; (left) note the vacuole. This can be confused with an I. bütschlii cyst; however, an E. nana cyst contains four nuclei, not just one. doi:10.1128/9781555819002.ch21.f13

(Upper, left and right) Trophozoites of Iodamoeba bütschlii (note the very large karyosome within the nucleus). (Lower, left) Cyst of I. bütschlii wet mount stained with iodine (note the large glycogen vacuole—stains brownish with iodine); (right) I. bütschlii cyst on trichrome-stained permanent stain (also note the large vacuole—appears clear on permanent stain). doi:10.1128/9781555819002.ch21.f14

Life cycle of Blastocystis spp. (A) Cyst forms are excreted in the feces of infected hosts. (B) Humans acquire infection by consumption of food or water contaminated with feces containing cysts. (C) Excystation occurs in the large intestine to release the vacuolar form. The vacuolar form (C1) can transform into the granular form (C2) or the ameboid form (C3) and vice versa. The vacuolar form multiplies by binary fission (C4) (other modes of reproduction such as plasmotomy and budding can also occur). The vacuolar form undergoes encystation in the lumen of the large intestine to produce the cyst form, which is shed in the feces. (Adapted with permission from references 55 and 59 .) doi:10.1128/9781555819002.ch21.f15

Various forms of Blastocystis. (a) Vacuolar forms of Blastocystis having a large centrally placed vacuole showing extensive variation in size (arrows). (b) Granular forms with distinct granules filling the central body. (c) Ameboid form with characteristic pseudopodia. (d) Cyst forms. Note the smaller size and the characteristic refractile cyst wall surrounded by loose irregular outer coat. Bar, 10 μm. (Reproduced from reference 58 .) doi:10.1128/9781555819002.ch21.f16

(Top, middle) Stained central-body forms of Blastocystis spp.; note the multiple nuclei around the edges, outside the central-body area. (Bottom) Blastocystis central-body forms in iodine wet mounts; note dividing form in right image (binary fission) and the large central “vacuole.” doi:10.1128/9781555819002.ch21.f17