Microbiology-GI Parasites

Question 1

Unicellular parasites

Answer 1

Protozoa

Question 2

Parasites to include, flat worms, round worms, ticks and mosquitos

Answer 2

Helminths

Question 3

Definitive host

Answer 3

Host in which the parasite lives and passes on the infectious egg or larva (mosquito in malaria)

Question 4

Intermediate host

Answer 4

Parasite has to infect this and may grow/change before going back to the definitive host (humans in malaria)

Question 5

Paratenic host

Answer 5

Rides around trying to get back to its definitive host (toxo tries to get back to a cat)

Question 6

Zoonosis

Answer 6

Disease man catches from animals

Question 7

What is amebiasis?

Answer 7

Infection by entamoeba histolytica, which is present in fecal matter

Question 8

What is the life cycle of entamoeba histolytica?

Answer 8

Ingestion of mature cyst -> cyst breaks open in small bowel -> trophozoites lodge in distal colon.

Question 9

What is clinical amebiasis? What if the patient is asymptomatic?

Answer 9

Extraintestininal invasion by entamoeba histolytica trophozoites that causes symptoms. If the patient is asymptomatic, they are a cyst passer.

Question 10

How do you diagnose someone with amebiasis?

Answer 10

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.

Question 11

How is amebiasis spread?

Answer 11

Fecal contamination of uncooked produce, water supply and flies

Question 12

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?

Answer 12

“Flask shaped” ulcers with a pin hole neck and wide base in the cecal region; also in the sigmoid, hepatic and splenic flexures.

Question 13

What is the difference between complicated and uncomplicated amebiasis?

Answer 13

Uncomplicated has involvement of the lymphatics and blood vessels. Complicated only involves the

Question 14

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?

Answer 14

Large unicellular organisms w/ “target nuclei”

Question 15

When do you include amebiasis on your differential list?

Answer 15

Anytime there is mucoid bloody diarrhea

Question 16

Symptoms of acute amebiasis

Answer 16

Weight loss, abdominal pain, tenesmus and fever

Question 17

Symptoms of chronic amebiasis

Answer 17

Constipation alternating with diarrhea and permanent lactose intolerance.

Question 18

A patient dies after weeks of diarrheal disease due to dehydration. Autopsy reveals infection by entamoeba histolytica. What is the structure shown below?

Answer 18

Ameboma, this is a cancerous lesion that can be cured with treatment.

Question 19

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?

Answer 19

1) Liver. #2) Lung. Also skin and brain.

Question 20

What is your diagnosis in this patient that has had alternating constipation and diarrhea for the past three months?

Answer 20

Entamoeba histolytica. Notice the red blood cells inside the trophozoites that defines pathogenic infection

Question 21

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?

Answer 21

Metronidazole or tinidazole, these are effective at getting rid at intestinal and extra-intestinal amebiasis.

Question 22

Why should you keep your head above water when swimming in water in warmer parts of the world?

Answer 22

Primary amoebic meningoencephalitis (PAM) from Naegleria fowleri….it basically melts your brain.

Question 23

Parasitic eye infection from using contacts without good hygiene that causes keratitis and granulomatous amoebic encephalitis (GAE).

Answer 23

Acanthamoeba and balamuthia

Question 24

Most prevalent intestinal parasitic infection in the US

Answer 24

Giardia lamblia

Question 25

How do you get infected with giardia lamblia?

Answer 25

1) Ingest cysts in contaminated food or water 2) Cysts become trophozoites and infect small intestine 3) Shed cysts in stool

Question 26

What type of diarrhea will you see with giardia lamblia?

Answer 26

Steatorrheaic and smelly because the parasite covers so much of the intestine that you get a malabsorption diarrhea.

Question 27

How do you diagnose a patient with giardia?

Answer 27

O & P x 3

Question 28

How do you treat giardiasis?

Answer 28

Metronidazole or tinidazole

Question 29

Severe parasitic watery diarrhea associated with swimming pools and apple cider that can be fatal in people who are immunocompromised.

Answer 29

Cryptosporidium

Question 30

Severe parasitic watery diarrheal disease associated with water, fresh produce and Nepal!

Answer 30

Cyclospora.

Question 31

How do cryptosporidium and cyclospora infect the host?

Answer 31

Oocysts sporulate in water or food -> Ingestion of food -> gets into enterocytes -> shed as cysts again

Question 32

How do you treat cyclospora?

Answer 32

Trimethoprim/sulfa (bactrim)

Question 33

WWI intestinal parasitic outbreak that mostly infects immunocompromised hosts

Answer 33

Isospora belli

Question 34

What are these giant things in the intestinal crypts that you might have gotten from the fish in your aquarium?

Answer 34

Balantidium coli

Question 35

How HIV patients get infected by microsporidia or myxozoa?

Answer 35

They have springs inside of them that inject the host