Gastrointestinal and urogenital protozoa.pptx

Gastrointestinal and urogenital protozoa

1. protozoa Hamza Imtiaz MC-MPMLT239-006 Microbiology

2. Protozoa Understanding the life cycle and pathogenesis of protozoa and helminths requires an explanation of certain terms Many protozoa have a life cycle consisting of a trophozoite , which is the motile, feeding, reproducing form surrounded by a flexible cell membrane, a cyst, which is the nonmotile , nonmetabolizing , nonreproducing form surrounded by a thick wall.

3. Certain protozoa, such as Leishmania and Trypanosoma , have flagellated forms called promastigotes or   trypomastigotes and nonflagellated forms called amastigotes .

4. Intestinal and Urogenital Protozoa organism Insect Vector Stages that Infect Humans Stage(s) in Humans Most Associated with Disease Important Stage(s) Outside of Humans Entameoba None Cyst Trophozoite causes bloody diarrhea and liver abscess Cyst Giardia None Cyst Trophozoite causes watery diarrhea Cyst Cryptosporidium None Cyst Trophozoite causes watery diarrhea Cyst Trichomonas None Trophozoite Trophozoite causes vaginal discharge none

5. Entamoeba Histolytica   Entamoeba histolytica  is well recognized as a pathogenic ameba, associated with intestinal and extraintestinal infections. 

6. Lifecycle

7. Pathogenesis The ingested cysts differentiate into trophozoites in the ileum but tend to colonize the cecum and colon. The trophozoites invade the colonic epithelium and secrete enzymes that cause localized necrosis. Little inflammation occurs at the site. By far the most frequent site of systemic disease is the liver, where abscesses containing trophozoites form.

8. Acute intestinal amebiasis presents as dysentery (i.e., bloody, mucus-containing diarrhea) accompanied by lower abdominal discomfort. Chronic amebiasis with low-grade symptoms such as occasional diarrhea, weight loss, and fatigue also occurs

9. E. histolytica can be distinguished from other amebas by two major criteria: The first is the nature of the nucleus of the trophozoite . The E. histolytica nucleus has a small central nucleolus and fine chromatin granules along the border of the nuclear membrane. The nuclei of other amebas are quite different. The second is cyst size and number of its nuclei. Mature cysts of E. histolytica are smaller than those of Entamoeba coli and contain four nuclei, whereas E. coli cysts have eight nuclei.

10. Serologic testing is useful for the diagnosis of invasive amebiasis . The indirect hemagglutination test is usually positive in patients with invasive disease but is frequently negative in asymptomatic individuals who are passing cysts.

11. Metronidazole ( Flagyl ) in case of intestinal amebiasis . Asymptomatic cyst carriers should be treated with iodoquinol or paromomycin .

12. Properties Giardia Cryptosporidium Dormant Stage Cyst Oocyst Infection Causing Stage The trophozoite is pear-shaped with two nuclei, four pairs of flagella, and a suction disk with which it attaches to the intestinal wall. Oocysts release sporozoites , which form trophozoites Clinical Findings Watery ( nonbloody ), foul-smelling diarrhea is accompanied by nausea, anorexia, flatulence, and abdominal cramps persisting for weeks or months Watery, nonbloody diarrhea causing large fluid loss Diagnosis Stool examination Sting test Finding oocysts in fecal smears when using a modified Kinyoun acid-fast stain Giardia and Cryptosporidium

13. Giardia  cysts can contaminate food, water, and surfaces, and they can cause giardiasis when swallowed in this infective stage of their life cycle. Infection occurs when a person swallows  Giardia   cysts from contaminated water, food, hands, surfaces, or objects.  When  Giardia   cysts are swallowed, they pass through the mouth, esophagus, and stomach into the small intestine where each cyst releases two trophozoites through a process called excystation . The   Giardia   trophozoites then feed off and absorb nutrients from the infected person.   Giardia   trophozoites multiply by splitting in two in a process called longitudinal binary fission, remaining in the small intestine where they can be free or attached to the inside lining of the small intestine.  The  Giardia   trophozoites then move toward the colon and transform back into cyst form through a process called encystation . The  Giardia  cyst is the stage found most commonly in stool . Lifecycle of Giardia

14. Excystation takes place in the duodenum, where the trophozoite attaches to the gut wall but does not invade the mucosa and does not enter the blood stream. The trophozoite causes inflammation of the duodenal mucosa, leading to malabsorption of protein and fat. IgA deficiency greatly predisposes to symptomatic infection Pathogenesis

15. Oocysts are ingested from contaminated sources . Oocysts excyst in the small intestine, releasing sporozoites . Sporozoites attach to intestinal epithelial cells and develop into trophozoites . Trophozoites undergo asexual reproduction to produce merozoites . Some merozoites develop into sexual gametocytes ( macrogametes and microgametes ), leading to fertilization and the formation of new oocysts . Oocysts are excreted in feces and can contaminate the environment, ready to infect new hosts. Lifecycle of Cryptosporidium

16. The organism is acquired by fecal–oral transmission of oocysts from either human or animal sources. The oocysts excyst in the small intestine, where the trophozoites (and other forms) attach to the gut wall. Invasion does not occur. The jejunum is the site most heavily infected. Pathogenesis

17. Trichomonas vaginalis causes trichomoniasis . Infectious Stage T. vaginalis is a pear-shaped organism with a central nucleus and four anterior flagella. It has an undulating membrane that extends about two-thirds of its length. It exists only as a trophozoite ; there is no cyst form. Trichomonas

18. Clinical Findings In women, a watery, foul-smelling, greenish vaginal discharge accompanied by itching and burning occurs. Infection in men is usually asymptomatic, but about 10% of infected men have urethritis . Laboratory Diagnosis In a wet mount of vaginal (or prostatic) secretions, the pear-shaped trophozoites have a typical jerky motion. There is no serologic test. Treatment & Prevention The drug of choice is metronidazole ( Flagyl )