Exam VI - Mycoses & Parasitology

Question 1

Fungal Structure

Answer 1

Cell wall composed of chitin and glucan Ergosterol instead of cholesterol These are potential targets because they are hard to treat since they are eukaryotic like we are = not many anti-fungals on the market

Question 2

Morphology of Fungi Form

Answer 2

Yeasts: usually unicellular, reproduce via budding creating pseudohyphae and via binary fission Ex. Candida albicans

Question 3

Morphology of Mold Form

Answer 3

Multicellular have hyphae, which altogether create mycellium Ex. Aspergillus fumigatus

Question 4

Dimorphism

Answer 4

Some fungi have both yeast and mold forms: thermally dimorphic 37° C (human body temp): yeast form

25° C (room temp): mold form

“yeast in the beast, mold in the cold”

they switch between these forms depending on the environment

Question 5

Mycoses: Classification by Location

Answer 5

Superficial – infect skin, hair, and nails

Cutaneous – keratinized layer of skin, hair, and nails caused by dermatophytes; itchy scaling of skin with ring like patches Systemic – goes throughout the body; kidney, lung, brain, etc.; thermally dimorphic

Opportunistic – candida albicans because we have it all the time, but when the balance in the body is disrupted it causes infection; immunocompromised AND healthy individuals

Question 6

Systemic Mycoses

Answer 6

Thermally dimorphic with ability to cause infections in both healthy and immunocompromised Respiratory infections Capable of disseminating to the rest of the body “endemic” geographic regions

Blastomyces dermatitidis

Coccidiodes immitis

Histoplasma capsulatum

Paracoccidiodes brasiliensis

**The signs and symptoms of these fungi are essentially the same, but the location of the fungi, morphology, etc. will help you ID the exact culprit

Question 7

Saprobic and Parasitic Phases of Endemic Dimorphic Fungi

Answer 7

A: Histoplasma capsulatum

B: Blastomyces dermatitidis

C: Paracoccidioides brasiliensis

D: Coccidioides immitis

* All types of Systemic Mycoses

Question 8

Blastomyces dermatitidis

Answer 8

Systemic Mycoses
Transmission: inhalation of conidia
Soil and leaf litter
Conversion from conidia (infectious form) to yeast (parasitic form) in the lungs
Endemic areas: Southeastern U.S. Ohio-Mississippi River Valleys, Great Lakes region
“broad based budding yeast”

Don’t know you inhaled it, and once in the lungs they will sense the temp change and morph into the yeast form

As it buds off, the base (parent cell) is broader than the daughter cell

Infection: lower respiratory tract
Asymptomatic
Acute onset flu like symptoms: myalgia, chills, malaise, fever
More severe: pneumonia like, high fever, non-productive cough, infiltrates on X-ray – throughout both lungs

Question 9

Coccidiodes immitis

Answer 9

Systemic Mycoses respiratory infection
Transmission: inhalation of conidia
Found in the soil of the desert Southwest U.S., California, Mexico, Central & South America

Spherule = the name for the yeast form of coccidiodes immitis

Takes hours (12-24) to change between mold and yeast forms

Infection is asymptomatic
Self limiting flulike illness: fever, chest pain, cough, and weight loss

Can progress and disseminate to other parts of the body - dangerous

Question 10

Histoplasma capsulatum

Answer 10

Systemic Mycoses: Spelunker’s lung
H. capsulatum is found throughout the world and is endemic in certain areas of the United States including states bordering the Ohio River Valley and the lower Mississippi River.
Positive histoplasmin skin tests occur in as many as 80% of the people living in areas where H. capsulatum is common.

Grows in soil and material contaminated with bat or bird droppings.
Spores become airborne when contaminated soil is disturbed.

Transmission: inhalation of conidia

Symptoms: acute primary histoplasmosis, asymptomatic, acute symptomatic primary histoplasmosis; largely dependant on # of spores inhaled
Fever, headache, cough, chills, chest pain, weight loss and sweats

TB vs. Spelunker’s Lung: TB has bloody sputum

Question 11

Paracoccidioides brasiliensis

Answer 11

Systemic Mycoses
Transmission: inhalation of conidia
Found in soil in Central and South America
Asymptomatic infection common in children
Microscopy: yeast form with many cells budding off called the“Pilot’s wheel”

Symptomatic infection in males 30-50 years of age
Persistent cough with sputum, chest pain, fever, weight loss,
Can disseminate to mucosal surfaces, causing lesions of the mouth, nose & GI tract and can go dormant until reactivation

Question 12

Tissue Tropism of Parasites

Answer 12

CNS: amebae, malaria, Toxoplasma, trypanosomes

Urogenital Tract: trichomonas

Skin: Leishmania

Blood: malaria and trypanosomes

Liver: entamoeba and Leishmania

Intestine: giardia, Cryptosporidium, Entamoeba, Cyclspora, and microsporidia

Question 13

Modes of Transmission

Answer 13

Intermediate Host- accidental ingestion of larvae

Fecal/Oral Route: accidental ingestion of larvae from feces of infected host

Active Skin Penetration: larval stages invade through skin

Injection via Insect: larval stages develop to infectivity in insect intermediate host

Question 14

Giardia lamblia

Answer 14

Protozoa with 2 stages

1. Cysts (resistant stage)- usually in water typically shed in stools; Infective stage spread by fecal-oral route
2. Trophozoites (active stage) – causes problems in GI tract such as cramps and diarrhea; live in the intestine

Streams, lakes, wild and domestic animals
Contaminated water, fruits and vegetables
Resistant to chlorination
Transmission: ingestion (10-25 cysts)
Gastric acid causes change from cyst to trophozoite
Trophozoite attaches to intestinal villi causing localized tissue damage
Incubation: 1-4 weeks, average 10 days
Symptoms: acute, onset of foul smelling, watery diarrhea, cramps, flatulence, and steatorrhea lasting 10-14 days
Diagnosis: microscopy of stool sample, 1/day for 3 days

Question 15

Naegleria fowleri

Answer 15

Protozoa: amoeba
Soil at the bottom of lakes
Seasonal: summer, warmer temperatures
Transmission: contact with nasal mucosa
Swimming, water skiing, immersed in water
Invades nasal mucosa, travels to the brain - causes death most of the time, therefore not a successful parasite

Netty pot cases
Primary Amebic Meningoencephalitis (PAM)
Intense frontal headache, sore throat, fever, altered sense of taste and smell, nuchal rigidity - this is usually indicative of meningitis
Death: 4-5 days
Diagnosis: CSF sample will contain ameba and red blood cells
Life Cycle: cyst (found in environment), trophozoite, flagellated form, promitosis back into trophozoite (infectious form) to penetrate the nasal muscae and travels to CSF and brain tissue

Question 16

Helminths

Answer 16

parasitic worms
1. Flatworms: Tapeworms: cestodes and Flukes: trematodes
2.Roundworms: nematodes
Most common helminth: It has no geography preference = pinworms; infects mostly children

Question 17

Enterobius vermicularis

Answer 17

Pinworms
Ingestion of eggs, which migrate to large intestine
Mature into adults (2-6 weeks)
Females lay thousands of eggs in the perianal folds
Symptoms: pruritus, loss of sleep, fatigue

Life Cycle: eggs on perianal folds, embryonated eggs ingested by human, larvae hatch in small intestine, adults in lumen of cecum, gravid females migrates to perianal folds at night to lay eggs

Children, day cares, schools
Scotch tape test on anus
Treat entire family as a precaution

Question 18

Dracunculus medinensis

Answer 18

Nematode (roundworm) in Asia & Africa
Ingestion of intermediate host: copepod (type of cyclops)
Worm larvae released in the stomach, which penetrate through GI walls and migrate to extremities (ams and legs) to cause tissue damage
Forms a vesicle on the skin (1yr after exposure)
Ulcerates (blister), female worm is exposed
Upon contact with water, larvae are released
Ingested by copepods
Animals can also be reservoirs
Life Cycle: larva escapes from skin lesion, ingested in cyclops in the water, goes through 2nd and 3rd larval stages, human ingested cyclops, penetrates intestinal wall, females travel to extremities and lay eggs (dx stage)