Microbiology: Cases 46-55

Front 1

What forms does E. histolytica exist as?

Back 1

Trophozoite:
Fragile and cannot live outside the host
One nucleus
Cyst:
Infective form
Able to withstand the low pH of the stomach
4 nuclei

Front 2

How is E. Histolytica transmitted?

Back 2

Ingestion of mature cysts in fecally contaminated food, water, or hands.

Front 3

In pts with persistant infection of E. Histolytica, what is of immediate concern?

Back 3

the trophozoite may invade the blood stream and reach extraintestinal tissues such as the liver. In the liver, they irreversably destroy hepatocytes and cause liver abscess.

Front 4

36 y/o man presents with 10 days of bloody, mucus filled diarrhea. He just returned from india. PE shows fever, diffuse abd tenderness, and rectal exam was positive for blood. Stool antigen test was positive for amebic agent. Most likely agent? Txmt?

Back 4

E. Histolytica
Metronidazole

Front 5

Where does exocystation occur in E. Histolytica? How does the trophozoite bind in the intestinal mucosa?

Back 5

Small intestine
The trophozoite adhere to mucosal cells be lectin-binding receptors

Front 6

Amebic cytotoxins allow trophozoites of E. Histolytica to do what?

Back 6

Invade the colon with lysis of epithelial cells and PMN's, which cause release of hydrolytic enzymes that damage the mucosa leading to amebic colitis and flask-shaped ulcers

Front 7

Ulcer characterization in E. histolytica colitis

Back 7

Flask-shaped

Front 8

Produces an extracellular cysteine proteinase that degrades collagen and elastin

Back 8

E. Histolytica

Front 9

35 y/o male with AIDS presents with complaint of several weeks of watery diarrhea. He also complains of low grade fever, nausea, and anorexia. He has not been on his HAART. CBC shows increased WBC w/ neutrophil prominence. Acid-fast stool stain showed a protozoal infection. Most likely cause? Txmt?

Back 9

Cryptosporidium parvum
Intravenous rehydration and restoration of HAART w/ paromomycin. In most other people, it is self-limited.

Front 10

Intracellular acid-fast coccidian protozoal agent

Back 10

C. parvum

Front 11

Site of infection in C. parvum. How does diarrhea develop?

Back 11

Jejunum:
The sporozoites adhere to the absorptive int epithelial cells and focally disrupt the microvilli and envelop themselves in the host cell membranes via "intracellular but extracytoplasmic" process. Diarrhea develops when the intestinal absorption is impaired.

Front 12

Organism whose merozoites can undergo sexual reproduction within the same human host to regenerate oocysts, which are infective on excretion, thus permitting the direct and immediate fecal-oral transmission in men like John Hatenalas.

Back 12

C. parvum

Front 13

Organism whose pathogenesis includes invading the microvilli, where they complete their entire life cycle, and are found as "intracellular but extracytoplasmic" within host cell membranes.

Back 13

C. parvum

Front 14

3 y/o girl was brought to the ER following a 3-week hx of nausea, poor appetite, and abd pain. She had no bowel movements for 3 days. PE showed no fever, but abd was distended and tender. CBC showed normal WBC but eosinophil dominance. Abd X-rays show intestinal obstruction. Most likely organism? Txmt?

Back 14

Ascaris lumbricoides
Mebenzadole

Front 15

If untreated, what may occur in Ascaris lumbricoides infection?

Back 15

Intestinal obstruction and inflammation of mucosa may lead to bowel perforation, peritonitis, and sepsis.

Front 16

Large intestinal nematode roundworm of humans. What form is infectious? How is it transmitted

Back 16

Ascaris lumbricoides
The eggs are not infectious, rather its the larval form.
Oral ingestion of fecally contaminated products containing eggs

Front 17

Most common method for diagnosing ascaris infection

Back 17

eggs within the stool

Front 18

Helminthic infections induce what inflammatory cellular responses

Back 18

TH2 responses characterized by eosinophilia and IgE

Front 19

Loeffler syndrome

Back 19

Eosinophilic pneumonia caused by larval migration from intestinal mucosa, into the portal, then the systemic circulation, and finally to the lungs. Here the larvae mature for up to 2 weeks and penetrate the alveolar walls. From the alveoli, the ascend the bronchial tree and are swallowed. When they reach the small int, they develop into adults and live in the lumen.

Front 20

Pathogenesis of ascaris lumbricoides

Back 20

larval migration from intestinal mucosa, into the portal, then the systemic circulation, and finally to the lungs. Here the larvae mature for up to 2 weeks and penetrate the alveolar walls. From the alveoli, the ascend the bronchial tree and are swallowed. When they reach the small int, they develop into adults and live in the lumen.

Front 21

49 y/o female presented with high fever, chills, jaundice, and upper abd pn. She is a recent immigrant from south america. One year before, she complained of pn in her R upper abd. She is a farmer who worked with sheepdogs. CBC is elevated. CT scan show a multi-loculated cyst with bile duct dilatation. Most likely organism? Txmt?

Back 21

Echinococcus granulosus causing echinococcosis (hydatid cyst disease).
Surgerical removal of the parasitic mass. DOC is albendazole.

Front 22

Transmission of this organism is from fecal contact of sheepdogs, or canines, where it resides in the small bowel

Back 22

Echinococcus granulosus

Front 23

Organism that causes abscess within the liver and obstruction of the biliary duct, which results in jaundice and biliary duct dilation

Back 23

Echinococcus granulosus

Front 24

The adult female of Strongyloides stercoralis usually resides where?

Back 24

Duodenum and jejunum

Front 25

Uninfective larvae hatched from the eggs of a female S. stercoralis. Infective?

Back 25

Rhabditiform larvae
Filariform larvae

Front 26

Organism who is able to penetrate intact skin

Back 26

Strongyloides via filariform larvae

Front 27

Organism that causes an urticarial, raised, erythematous rash, the most common dermatologic manifestation of parasitic infections

Back 27

Strongyloides

Front 28

Organism whose worms burrow into the mucosa and cause GI symtpoms such as abd pn, diarrhea, and in heavy infections, ulceration and sloughing of int mucosa

Back 28

Strongyloides

Front 29

42 y/o male presents with 3 weeks of worsening diarrhea, abd pn, and fevers. He also complains of an itchy rash over his buttocks and groin area. CBC shows eosinophilic dominance. Most likely organism? Txmt?

Back 29

S. stercoralis
Ivermectin

Front 30

Katayema fever is associated with?

Back 30

Acute Schistomiasis:
4-6 wks after infection, at the time of egg release.
Fever, cough, abd pn, diarrhea, eosinophilia, and hepatosplenomegaly.

Front 31

Diagnosis of this parasite is via eggs in the urine. Where does in live?

Back 31

S. haematobium:
lives in the venous plexus near the urinary bladder and ureters.

Front 32

Niche of S. mansoni and japonicum

Back 32

Inferior mesenteric vein
Superior mesenteric vein of both the large and small intestines

Front 33

Intermediate host of schistomiasis

Back 33

snails

Front 34

Transmission of schistomiasis to humans

Back 34

Penetration of intact skin with infective cercariae, which are released from infected snails. Once within, the human host they shed their tail and become schistosomulae, where they migrate through tissues and take up residence within veins.

Front 35

Life cycle of S mansoni begins with?

Back 35

eggs shed within feces of a pt. These eggs then hatch and release miracidia which swim and infect snails, which produce cercariae

Front 36

Form of s. mansoni that infect snails

Back 36

miracidia

Front 37

Most diagnostic method for identifying schistosomiasis

Back 37

eggs in the stool

Front 38

Chronic schistosomiasis is due to?

Back 38

Immunolgic rxns of to schistosoma eggs trapped in tissues. Including IgE, eosinophilia, via activation of TH2 cells that are the main pathogenic element.

Front 39

Organism that causes a TH2 response that leads to profound granulomatous rxn resulting in portal hypertension with hematemesis, and hepatosplenomegaly, with collagen deposition and fibrosis within the hepatocytes.

Back 39

Schistosomiasis:
Ultimately leads to cirrhosis

Front 40

DOC in txmt of schistosomiasis

Back 40

Praziquantel

Front 41

25 y/o male presents with 2 week hx of diarrhea, nausea, flatulence and lack of appetite after backpacking in the Rocky mountains. Diarrhea was initially watery, but now greasy and foul. He now feels bloated. He has had no fever or chills. Duodenal biposy shows an intestinal pear shaped flagellate protozoa. Organism? Transmission?Txmt?

Back 41

Giardia Lamblia
Fecally contaminated water
Metronidazole

Front 42

How many pairs of flagella does G. lamblia have?

Back 42

4

Front 43

G. Lamblia exists in what forms?

Back 43

Trophozoite:
pathogenic form
Cyst:
Infective
Survives the pH of the stomach

Front 44

How may cysts be detected in diagnosis of G. Lamblia

Back 44

Using a direct mount of feces. Trophozoites may be seen in a duodenal biopsy if 3 consecutive fecal tests are negative.

Front 45

Produces an IgA protease that allows for adherence to the organism

Back 45

G lamblia

Front 46

Organism that initiates infection by being taken up by macrophages in peyer patches. From here a T cell mediated inflammatory response leads to crypt hyperplasia and microvilli injury in the brush border, resulting in watery and then greasy, foul stools.

Back 46

G lamblia

Front 47

Mechanism of malabsorption diarrhea in G. Lamblia

Back 47

Trophozoites lead to disruption of the microvilli of the brush border, causing villi atrophy (via proteinase or lectin-binding protein).