Microbiology-GI Parasites Flashcards
Unicellular parasites
Protozoa
Parasites to include, flat worms, round worms, ticks and mosquitos
Helminths
Definitive host
Host in which the parasite lives and passes on the infectious egg or larva (mosquito in malaria)
Intermediate host
Parasite has to infect this and may grow/change before going back to the definitive host (humans in malaria)
Paratenic host
Rides around trying to get back to its definitive host (toxo tries to get back to a cat)
Zoonosis
Disease man catches from animals
What is amebiasis?
Infection by entamoeba histolytica, which is present in fecal matter
What is the life cycle of entamoeba histolytica?
Ingestion of mature cyst -> cyst breaks open in small bowel -> trophozoites lodge in distal colon.
What is clinical amebiasis? What if the patient is asymptomatic?
Extraintestininal invasion by entamoeba histolytica trophozoites that causes symptoms. If the patient is asymptomatic, they are a cyst passer.
How do you diagnose someone with amebiasis?
O&P (stool examination) x 3. These parasites are intermittent shedders and you should do it three times. If they have extra intestinal infection you have to do needle biopsy of abscesses looking for “anchovy paste” pus.
How is amebiasis spread?
Fecal contamination of uncooked produce, water supply and flies
A patient dies after weeks of diarrheal disease due to dehydration. Autopsy reveals infection by entamoeba histolytica. What would you expect to see on autopsy of the patient’s intestines?
“Flask shaped” ulcers with a pin hole neck and wide base in the cecal region; also in the sigmoid, hepatic and splenic flexures.
What is the difference between complicated and uncomplicated amebiasis?
Uncomplicated has involvement of the lymphatics and blood vessels. Complicated only involves the
A patient dies after weeks of diarrheal disease due to dehydration. Autopsy reveals infection by entamoeba histolytica. What would you expect to see on histology of the patient’s intestines?
Large unicellular organisms w/ “target nuclei”
When do you include amebiasis on your differential list?
Anytime there is mucoid bloody diarrhea
Symptoms of acute amebiasis
Weight loss, abdominal pain, tenesmus and fever
Symptoms of chronic amebiasis
Constipation alternating with diarrhea and permanent lactose intolerance.
A patient dies after weeks of diarrheal disease due to dehydration. Autopsy reveals infection by entamoeba histolytica. What is the structure shown below?
Ameboma, this is a cancerous lesion that can be cured with treatment.
A patient dies after weeks of diarrheal disease due to dehydration. Autopsy reveals infection by entamoeba histolytica and odorless, sterile abscesses in different organs. In what organs are you likely to find these abscesses?
1) Liver. #2) Lung. Also skin and brain.
What is your diagnosis in this patient that has had alternating constipation and diarrhea for the past three months?
Entamoeba histolytica. Notice the red blood cells inside the trophozoites that defines pathogenic infection
A patient dies after weeks of diarrheal disease due to dehydration. Autopsy reveals infection by entamoeba histolytica and odorless, sterile abscesses in different organs. You decided to treat the patient before he died and he said that he had a metallic taste in his mouth. What drug did you prescribe him?
Metronidazole or tinidazole, these are effective at getting rid at intestinal and extra-intestinal amebiasis.
Why should you keep your head above water when swimming in water in warmer parts of the world?
Primary amoebic meningoencephalitis (PAM) from Naegleria fowleri….it basically melts your brain.
Parasitic eye infection from using contacts without good hygiene that causes keratitis and granulomatous amoebic encephalitis (GAE).
Acanthamoeba and balamuthia
Most prevalent intestinal parasitic infection in the US
Giardia lamblia
How do you get infected with giardia lamblia?
1) Ingest cysts in contaminated food or water 2) Cysts become trophozoites and infect small intestine 3) Shed cysts in stool
What type of diarrhea will you see with giardia lamblia?
Steatorrheaic and smelly because the parasite covers so much of the intestine that you get a malabsorption diarrhea.
How do you diagnose a patient with giardia?
O & P x 3
How do you treat giardiasis?
Metronidazole or tinidazole
Severe parasitic watery diarrhea associated with swimming pools and apple cider that can be fatal in people who are immunocompromised.
Cryptosporidium
Severe parasitic watery diarrheal disease associated with water, fresh produce and Nepal!
Cyclospora.
How do cryptosporidium and cyclospora infect the host?
Oocysts sporulate in water or food -> Ingestion of food -> gets into enterocytes -> shed as cysts again
How do you treat cyclospora?
Trimethoprim/sulfa (bactrim)
WWI intestinal parasitic outbreak that mostly infects immunocompromised hosts
Isospora belli
What are these giant things in the intestinal crypts that you might have gotten from the fish in your aquarium?
Balantidium coli
How HIV patients get infected by microsporidia or myxozoa?
They have springs inside of them that inject the host
