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38 Cards in this Set
- Front
- Back
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Describe the characteristics of protozoans.
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Eukaryotic, single-celled organism
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What are the 2 stages of Giardia lamblia?
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Trophozoite: feeding stage, teardrop shaped, flattened, 2 nuclei, adhesive disc
Cyst: Environmentally resistant/infective stage, Oval, Chitin cyst wall (hyalin), 2-4 nucleii (4 - older cysts) |
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Describe Giardia Iamblia's lifestyle?
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2 stages:
Cyst (feces) Trophozoite (Duodenum: eats mucus secretions) Non-invasive 1cyst -->2 Trophs |
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An 8-year old child is brought to the clinic because of intermittent episodes of watery diarrhea. History discloses that the child, inreality, has been ill w/ abdominal cramps and non bloody diarrhea for several weeks—a few days after the family returned from a camping vacation in the Colorado Rockies. Physical exam reveals that the abdomen is slightly distended. A stool sample is negative for ova and protozoans but the GSA is positive. Tinidazole therapy is initiated, & the parents are advised to only drink purified water during future camping trips.
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Giardia:
Infective dose = 100 cysts 2 wk incubation NO blood NO tissue penetration Malabsorption (Vit. B12 deficiency) Explosive Diarrhea |
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What are some defenses and what is the body's immunity to Giardia?
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Human Milk - giardiacidal (IgA)
-lack IgA = recurring/chronic infections Ab's (Tcell dependent), complement, Oxidative microbicidal activity (phagocyte)s - kill Trophs Protective immunity develops |
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How is Giardia transmitted? controlled?
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Waterborne, drink clean water, avoid fecal contamination (boiling/iodine), personal hygiene
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What is the epidemiology of Giardia?
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Worldwide
Traveler's Disease Very contagious Fecal contamination Waterborne Zoonotic - beavers (USA) Prevalence - children |
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What is the target population for Giardia?
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Children in day care/close contact
Homosexuals Backpackers/Campers People who drink from shallow wells/ surface water. |
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How do you ID Giardia?
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Stool sample (-) ova/protozoa
GSA (+) (100%sens/spec) Many samples needed |
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What is the treatment for Giardia?
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Metronidazole (DOC) - 5-7d
Albendazole - 5d Tinidazole - 1dose Furazolidone (children) |
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Whats the difference between Amoebic dysentery and Giardia in terms of location in the body?
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Amoebic Dysentary - Large intestine
Giardia - Duodenum |
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What is the causative agent of Amoebic dysentery and what damage does it have on the body?
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Entamoeba histolytica,
-produce colitis or liver abscess |
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What is the morphology of Entamoeba histolytica?
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Troph - 1 nuc; central endosome
Cyst - 4 nucs; round-oval; blunt chromatoidal bar |
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Describe the stages/lifecycle of Entamoeba histolytica?
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Fecal ingestion
Troph: feeding, virulence -Caecum, colon, extraintestinal Cyst: infective, protection -Colon |
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A college student who regularly participates in medical missions to Guatemala is hospitalized because of right upper quadrant pain, low-grade fever, & severe head-
aches. Accordingly, the fever & pain has persisted off & on for about 6 months. In addition, the student often experiences bouts of bloody diarrhea. Stool sample is positive for quadrinucleate amebas, w/ a positive ELISA for Entamoeba histolytica. A CT scan reveals a 3-cm cyst-like structure, a possible liver amoebic abscess. Metronidazole-iodoquinol therapy is prescribed, & the student eventually recovers. Advice is given on safe travel in third-world countries. |
Entamoeba histolytica
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Entamoeba histolytica presents how?
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Bloody diarrhea
Possibly Asymptomatic for 10d |
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Entamoeba histolytica causes death how?
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Peritonitis (gut perforation) & cardiac failure & exhaustion
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Entamoeba histolytica in the intestine can present how?
Entamoeba histolytica in the extraintestinal space presents how? |
Assymptomatic, acute colitits, fulminant colitits, ameboma
Hepatic, Pleuropulmonary, cerebral, GU (Flask-shaped Ulcer) |
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What are Entamoeba histolytica's Virulence Factors?
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Lectin - adhesins
Cysteine proteinases -degrade mucus, antibody, complement, cellular matrix Phospholipases - disrupt membranes Amebopore - cytolytic activity |
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What is the epidemiology of Entamoeba histolytica?
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Worldwide
Transmission - fecal contamination, water & foodborne, mechanical vectors (flies) Public health - notifiable (CDC) |
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How do you ID Entamoeba histolytica?
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Diagnostic: cyst, troph
Radiologic: Extraintestinal EIA: intestinal/invasive |
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How is Entamoeba dispar different from Entamoeba histolytica?
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Non-invasive commensal parasite
Lacks cysteine proteinases |
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What organisms are fecal contamination indicators?
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Entamoeba hartmanni
Entamoeba coli Endolimax nana Iodamoeba buetschlii Blastocystis hominis |
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What's the treatment for Entamoeba histolytica?
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Dependent on location:
Intestinal: Metronidazole Tinidazole + Iodoquinol Hepatic cyst: Metronidazole Tinidazole Liver abscess resolves with chemo |
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How do you control Entamoeba histolytica?
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Drink clean water only (waterborne pathogen)
Prevention: avoid fecal contamination water purification personal hygiene NO prophylaxis *cysts are resistant to chlorine |
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A tourist who travels to Latin America, presents abdominal pain and bloody diarrhea. A stained
fecal sample under oil immersion reveals the diagnostic stage (figure). If treatment is withheld, the tourist is in danger of developing which of the following conditions? |
Hepatic amoebiasis
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A child who lives in a rural community in the Appalachia presents with abdominal pain, anorexia, & watery diarrhea. Fecal smear reveals an abundance of cyst-like structures (figure). The microbe most likely responsible is:
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Giardia
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What are the organisms responsible for Cryptosporidiosis? Describe its patient population and does it require treatment?
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Cryptosporidium parvum
Cryptosporidium hominis Children and Immunosupressed Self-limiting |
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Describe the pathogenesis of:
Cryptosporidium parvum & Cryptosporidium hominis |
Infects GI (parasitophorous vacuole)
Causes: Diarrhea, Fever, Malaise Self-Limiting Person to Person transmission: with Fecal contamination Zoonotic (manure-contaminated drinking water) Assoc. with AIDS Tx: DOC: nitazoxanide or Paromomycin or Azithromycin |
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how do you ID Cryptosporidium parvum
& Cryptosporidium hominis? |
Acid fast stain and ELISA
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An AIDS patient, who is a competitive swimmer, presents to the ER w/ severe diarrhea that is reminiscent of cholera. The patient is severely wasted (cachectic) & is admitted. Antigen-detection assay of the stool is positive for Cryptosporidium. Unfortunately, despite aggressive antiparasitic therapy, the patient dies within 2 days. As indicated on the chart, the patient had been warned not to swim in public pools.
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Cryptosporidium parvum and Cryptosporidium hominis are not killed by chlorine
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Describe Cyclosporiasis?
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Diarrheagenic protozoan disease with Latin America connections. Autoflourescent oocyst is larger than Cryptosporidium.
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What are some characteristics of Cyclospora cayetanensis?
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Oocysts larger than Cryptosporidium
Diarrhea, cramps, low grade fever Cosmo (Traveler's Disease) Acid-fast/autofluoresces Tx: TMP-SMX |
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A company doctor of a food distribution business in Maryland reports to the state health dept that many employees who attended a company luncheon came down w/ a gastrointestinal illness. The illness is marked w/ diarrhea, nausea, vomiting, abdominal cramps, & mild fever. Most of the patients started feeling sick w/in 1 wk of the luncheon. Frequency of diarrhea stools ranged from 3–35/day. All cases are laboratory confirmed. The health dept reports that the most likely vehicle for transmission is a basil-pestopasta salad. The salad was served cold; raspberries are not implicated. Prescriptions of TMP-SMX are offered to all patients.
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Cyclospora cayetanensis
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Describe Blastocystis hominis.
Tx: for Blastocystosis? |
Polymorphic protozoan
Large vacuole, multiple nuclei around rim of cytoplasm Associated w/ diarrhea & IBS Tx: Metronidazole |
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Describe Balantidium coli.
Tx: for Balantidiasis? |
Troph&cyst - macronucleus
Cilia evident on troph Infective stage - cyst (large) Large intestinal resident Diarrheagenic microbe Zoonotic - Pig (fecal borne) Tx: Tetracycline or Metronidazole |
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Microscopic ID of Balantidium coli?
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Macro nucleus - kidney shaped - metabolic function
Micronucleus - not visible - reproductive function |
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CDC investigates a series of outbreaks of cryptosporidiosis. The cluster of cases occurs in separate upscale suburban communities. Which of the following is the most plausible source of transmission for these outbreaks?
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Manure-contaminated drinking water
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