Amebiasis, Giardiasis Cryptosporidium, Trichomonmiasis Flashcards
In the lifecycle of protozoa, __ are the forms that eat, replicate and move, and the __ forms don’t do any of these things (except that they’re the infectious form)
In the lifecycle of protozoa, trophic forms are the ones that eat, replicate and move, and the cystic forms don’t do any of these things (except that they’re the infectious form)
**trophic forms responsible for pathology in host**
Pathogenic intestinal protozoa
E. histolytica: invasive; inhabits colon
Giardia intestinalis, Coccidia (Cryptosporidium, Cyclospora, Isospora): cause watery diarrhea, dysentery; inhabit small bowel
Non pathogenic intestinal protozoa
Other Entamoeba (besides histolytica)
3 parasites most common for causing diarrheal disease
Cryptosporidium parvum
Entamoeba histolytica
Giardia lamblia
Lifecycle of E histolytica inside host
ingested cyst >> trophic form in colon >> replication and escape into other organs >> excreted trophic forms (repeat of cycle)
Transmission of E histolytica is __
Tx: fecal-oral >> person to person, contaminated food/water
Trophozoites feed by __, colonize the colon and replicate by binary fission
Cysts have a __ that allow them to resist gastric acidity and are infective even in small doses
Trophozoites feed by phagocytosis and eat RBCs, colonize the colon and replicate by binary fission
Cysts have a strong cyst wall that allow them to resist gastric acidity and are infective even in small doses
Mechanisms of contact-mediated cytolysis for Entamoeba histolytica (3)
Adherence to epithelial cells via Gal/GalNac lectin
Cysteine proteases >> act on ECM
Amebapores >> pores in target cells
Which organism contributes to flask-shaped lesions pathology in the colon?
E histolytica
Presentation of amebiasis
Presentation: bloody diarrhea/dysentery, gradual onset (1+ week symptoms), ameboma
Dx of amebiasis
Microscopy of stool + fecal Ag testing +/- serology
Imaging and needle aspiration of liver abscess
Rx for amebiasis (asymptomatic carrier vs invasive disease)
Asymptomatic carrier: paromomycin/iodoquinol
Invasive disease: metronidazole/tinidazole
Which bug is this?
Giardia intestinalis (lamblia, duodenalis)
In Giardia, the __ stage colonizes the upper small intestine, attaches via “sucking disk” but doesn’t invade + replicates by binary fission
The __ stage is the infective stage passed in infected people’s feces
In Giardia, the trophozoite stage colonizes the upper small intestine, attaches via “sucking disk” but doesn’t invade + replicates by binary fission
The cyst stage is the infective stage passed in infected people’s feces
Giardiasis presentation
Main presentation: watery and foul smelling diarrhea (no blood) and abdominal cramps
(also note malabsorption due to damage to villi >> weight loss)
Giardiasis Dx and Rx
Dx: Microscopy and antigen testing
Rx: Metronidazole/Tinidazole/NITAzoxadine
Cryptosporidium life cycle
Lifecycle:; oocyst ingestion >> sporozoite formation in gut >> invasion of enterocytes >> sexual cycle >> thick/thin walled cyst formation
Thin walled cyst mediates auto re-infection (starts the cycle back), thick walled cyst is excreted and becomes the infectious form
Main method of Cryptosporidium transmission
Main method of transmission: contact with treated recreational water
Which group of people is especially susceptible to Cryptosporidium infection?
Immune compromised folks
Presentation of cryptosporidium
Very heavy and watery diarrhea
Marked weight loss
Dx of Cryptosporidiosis
Dx: modified acid fast stain
Rx for Cryptosporidiosis (immunocompetent vs immunocompromised host)
Rx for Cryptosporidiosis: immunocompetent pt >> nitazoxanide; immunocompromised pt >> HAART (basically remove the immunosuppression)
Cyclospora transmission
Fecal oral; mainly contaminated food/water/produce (US)
Cyclospora lifecycle
Lifecycle similar to other parasites (ingestion of sporulated oocyst >> infection in host >> excretion of unsporulated oocysts)
Note that the unsporulated oocysts need to sit in the environment for a while before they are infectious (considered the diagnostic stage)
**each oocyst contains 2 sporozoites. sporozoites infect the epithelial cells of the upper small intestine**
Presentation of cyclospora
Sudden onset
Fever, abdominal cramping
Frequent watery diarrhea
Dx for Cyclospora
Rx for Cyclospora
Microscopy of stool + PCR
Rx: TMP/SMX
Trichomonas vaginalis transmission
Sexual transmission
**bug only exists as trophozoite**
Presentation of Trichomonas vaginalis
Vaginal discharge, vulvovaginal soreness
In women, trichomonas vaginalis infection increases risk of __ infection
HIV-1
**
weakens the integrity of the epithelial barrier
decreases innate immunity and normal epithelial defenses
disrupts the lactobacilli dominated vaginal microbiome
Trichomonas vaginalis presentation in men
asymptomatic or have mild urethra discharge
(higher risk for HIV + unusual complications e.g. prostatitis)
Trichomoniasis Dx and Rx
Dx: wet mount microscopy; pap smears; cultures; NAATs
Rx: Metronidazole/Tinidazole
