Micro E3 pt 1

True fungal pathogens owe their virulence to thermal dimorphism. Define thermal dimorphism.

A change in form that is triggered by a change in temperature

Which class of fungal pathogens are transmissible by sharing infected towels and gym mats?

Dermatophytes

Which class of fungal pathogens develop long term immunity?

True pathogens

List the fungal pathogens discussed.

histoplasmosis, coccidioidomycosis, blastomycosis, Paracoccidioidomycosis, sporotrichosis, chromoblastomycosis, mycetoma, dermatophytes

Which true fungal pathogens cause Ohio River Fever?

Histoplasma capsulatum

Where is Histoplasma capsulatum most prevalent?

Midwestern and Southeastern US – follows the Ohio river valley

What type of soil does Histoplasma capsulatum thrive in?

Soil high in nitrogen content, especially in soil containing bird and bat droppings

What environments are associated with outbreaks of Histoplasma capsulatum?

Construction sites, parks, old buildings: where humans disturb spores

Describe the symptoms associated with a primary lung infection caused by Histoplasma capsulatum.

Mild cough, myalgias, malaise, +/- fever, night sweats, wt loss

Describe the microscopic appearance of Histoplasma capsulatum on a sputum smear.

Spherical “fish-eye” yeasts in macrophages

What true fungal pathogen causes coccidioidomycosis (Valley fever)?

Coccidioides immitis

What activities are commonly associated with outbreaks of Coccidioides immitis?

Farming, archeological digs, landslides, dust storms

What geographic location would you most likely find Coccidioides Immitis?

Southwestern US; especially in the San Joaquin Valley of California and southern Arizona

What are the Coccidioides immitis cells in the parasitic state called?

spherules

What pulmonary findings are consistent with severe coccidioidomycosis?

Fungomas: cavitary lesions/nodular growths in the lungs

What is the treatment for disseminated Coccidioides?

Itraconazole or fluconazole; Amphotericin B for severe cases

Blastomycosis is caused by which true fungal pathogen?

Blastomyces dermatitidis

What geographical location and environment is Blastomyces dermatitidis primarily found?

Midwestern and Southeastern US: forests, decaying wood, animal manure

Describe the microscopic appearance of Blastomyces dermatitis in sputum.

Large, ovoid yeasts w/ broad-based buds; “tiny lollipops”

Is serological testing recommended in Blastomycosis infections?

No, low sensitivity can cause false negatives and there is a high degree of cross-reactivity w/ other mycoses

What are the primary symptoms in blastomycosis pulmonary infection?

Flu-like sx, fever, chills, productive cough, myalgias, pleuritic chest pain

Which two true fungal pathogens cause paracoccidioidomycosis?

Paracoccidioides brasiliensis and Paracoccidioides lutzii

What geographical location are you most likely to find the pathogens that cause Paracoccidioidomycosis?

Mexico, Central and South America -most often Brazil

What occupations are you most likely to find the pathogens that cause Paracoccidioidomycosis?

Rural agricultural workers and plant harvesters

Describe the microscopic appearance of Paracoccidioidomycosis brasiliensis

Large, round or oval mother yeast cells w/ multiple attached narrow-necked buddying daughter yeast cells (“pilot’s wheel”) or mother yeast cell possessing only 2 attached daughter bud (“Mickey mouse head”)

Define subcutaneous mycoses.

Fungi are transferred directly into traumatized skin and can invade

What subcutaneous mycoses cause Rose-Gardener’s disease?

Sporothrix schenckii

Describe the clinical appearance of lymphocutaneous sporotrichosis.

Primary sore is accompanied by a series of nodules running along the lymphatic channels of the arm; advanced stages have ulcers and necrosis

What is the first line of treatment of lymphocutaneous sporotrichosis? Will heat applications help?

Itraconazole; heat will help resolve smaller infections

What is another name for Mycetoma?

Madura foot

What are the most causative fungi of Mycetoma?

Pseudallescheria or Madurella

Define cutaneous mycoses.

Infections strictly confined to the stratum coreum and epidermal tissues

Name the term that classifies cutaneous mycoses.

Dermatophytosis (tinea)

Name three dermatophytes discussed in class.

Tichophyton, Microsporum, Epidermophyton

List the medical term and the clinical presentation of scalp ringworm.

Tinea capitis: ranges from small, scaly patches to destruction of the hair follicle and permanent hair loss

List the medical term and the clinical presentation of beard ringworm.

Tinea barbae “barber’s itch”: ichty, nodules along the chin and beard of adult males

List the medical term and the clinical presentation of body ringworm.

Tinea corporis: inflamed, raised, scaly, red rings w/ serpigionous borders anywhere on smooth skin

List the medical term and the clinical presentation of groin ringworm.

Tinea cruris: “jock itch”; itchy, red, perineum groin, scrotal regions

List the medical term and the clinical presentation of foot ringworm.

Tinea pedis: peeling, scaly lesions that spreads in a “moccasin” pattern

List the medical term and the clinical presentation of nail ringworm.

Tinea unguium: thickening, accumulation of debris, cracking, discoloration; nail bed may become separated

List the medical term and the clinical presentation of hand ringworm.

Tinea manuum: occurs between digits and along the palms

What dermatophyte genera is most involved with tenia pedis?

Trichophyton

What would you find on a ring “wormy boi” positive skin scraping heated with KOH?

Branching, fungal mycelium

Define superficial mycoses.

Involves only the outer epidermal surface (non-invasive)

Name the fungal pathogens associated with white Piedra and describe its clinical presentation.

Trichosporon beigelii: whitish/yellowish colored masses develop on the shaft of scalp, pubic, or axillary hair

Name the fungal pathogens associated with black Piedra and describe its clinical presentation.

Piedraia hortae: dark-brown/black gritty nodules, mainly on scalp hairs but can be found on beard, mustache, and pubic hairs

Which superficial mycoses is caused by Malassezia furfur?

Tinea versicolor

Describe the clinical presentation of Tinea versicolor.

Mild, chronic scaling and causes a mottled discolored skin pigmentation

 Name the three topical medications or classification of medication involved in treatment of Tinea versicolor.

Antifungals (azoles, terbinafine, ciclopirox), selenium sulfide, zinc pyrithione

Name the opportunistic fungal pathogen that is often the cause of candidiasis.

Candida albicans

Describe the finding on a KOH slide in a patient with candidiasis.

Budding cells of varying size

Describe the clinical findings in oropharyngeal candidiasis and the patient population you would most likely this in.

“thrush” -thick, white adherent growth on mucous membranes of the mouth and throat: newborns, elderly, debilitated pts

Describe the clinical findings in esophageal candidiasis and the patient population you would most likely see each.

Painful, bleeding ulcerations, N/V: HIV/ immunocompromised pts

Describe the clinical findings in vulvovaginal candidiasis and the patient population you would most likely see each.

Itchy, whitish discharge, ulcerations, inflammation: adult women (inc risk when taking oral antibiotics, diabetic or pregnant)

Describe the clinical findings in cutaneous candidiasis.

Can occur anywhere on the skin w/ the correct environment; red, itchy, can produce a scald-like rash on neonates

Describe the clinical findings in intertriginous candidiasis.

Occurs in moist skin folds; red, itching

What is onychomycosis?

Fungal infection of the nail

Which opportunistic fungal pathogen causes cryptococcosis?

Cryptococcus neoformans

In which population would you see the disseminated form of Cryptococcosis?

Pts w/ AIDS, cancer, or diabetes

What type of stain is used to diagnosis cryptococcosis? Describe the microscopic findings.

India ink: halos around large spherical yeast cells

The opportunistic fungal pathogen Pneumocystis jirovecii causes what type of pneumonia in AIDs patients?

Pneumocystis pneumonia (PCP)

Why is amphotericin B a poor choice for treatment for AIDS pts w/ Pneumocystis pneumonia?

PCP lacks ergosterol making it uneffective

What is the recommended medication to Pneumocystis pneumonia?

Sulfamethoxazole/trimethoprim (Bactrim)

What two species of aspergillus are known to cause human illness?

Aspergillus fumigatus and Aspergillus flavus

What occupation is most associated with Aspergillus infections?

Farmers who breathe in clouds of conidia from the air of barns and silos

What is Aspergilloma?

Fungus balls formed in the lungs from spores of Aspergillus

What disease is caused by eating poisonous mushrooms?

Mycotoxicoses

What is the name of the most deadly wild mushroom?

Amanita phalloides “death angel”

How many trophozoites does a mature Entamoeba histolytica cyst release?

4

What is the clinical presentation of symptomatic intestinal amebiasis? What other organs are most commonly involved?

Dysentery, abdominal pain, fever, diarrhea (blood, mucus), wt loss; often also affects the liver, and sometimes the lungs, and heart

Which organism is known as a “brain-eating amoeba”?

Naegleria fowleri

Where is this Naegleria fowleri typically found?

Warm, standing water

What is the most effective drug against N. fowleri?

Amphotericin B

What type of protozoan is Balantidium coli?

Ciliated protozoa

How does a human acquire a Balantidium coli infection?

Ingesting cyst-containing food or water

What symptoms could Balantidium coli cause?

N/V, dysentery, abdominal colic

Which species of trichomonas causes a STD?

Trichomonas vaginalis

What percentage of individuals with T. vaginalis are asymptomatic carriers?

70%

What symptoms would women infected with T. vaginalis present with?

Foul-smelling, green/yellow frothy discharge; vulvitis; cervicitis; urinary frequency and dysuria

What symptoms would men infected with T. vaginalis present with?

Urethritis; prostatitis; thin, milky discharge

Giardia intestinalis AKA Giardia lamblia is usually found in what bodies of water?

Untreated water from a mountain stream or spring

Describe what the trophozoite form Giardia looks like.

Heart shaped; paired nuclei that resemble an “old man w/ glasses”

Describe the clinical presentation of Giardia.

Diarrhea, abdominal pain, dehydration, wt loss, flatulence

Name the organism and vector associated with African sleeping sickness.

Trypanosoma brucei; tsetse fly

Describe the first sign of infection and list the late symptoms associated with African sleeping disease.

Trypanosomal chancre -> intermittent fever, splenomegaly, LAD, arthralgia -> CNS, changes in personality, behavior, lassitude, sleep disturbances, etc

Name the organism and the vector associated with Chagas disease.

Trypanosoma cruzi; Reduviid bug (“kissing bug”)

Which organs are primary sites for chronic infection in Chagas disease?

Heart and brain

Name the vector associated with leishmaniasis.

Sand flies

Describe the clinical findings in cutaneous leishmaniasis.

Persistent skin lesions that start as small red papules -> darker and crust -> ulcer surrounded by dusky red skin

What are the primary causes of death in visceral leishmaniasis?

Hemorrhage, severe anemia, or secondary bacterial infections of mucous membranes

Which genre of apicomplexan parasites cause malaria?

Plasmodium

Describe the clinical presentation of malaria?

Fever paroxysms, Non-specific, may include tachycardia, tachypnea, chills, malaise, fatigue, diaphoresis, HA, cough, anorexia, N/V, abd pain, diarrhea, arthralgia, myalgias, +/- splenomegaly and hepatomegaly

What abnormalities will you see on a CBC in a patient with malaria?

Hemolytic anemia and thrombocytopenia

Describe the common findings on a peripheral blood smear of pts with malaria.

Ring-form trophozoites

Which apicomplexan parasite is associated with cat feces and eating undercooked lamb, beef, and pork?

Toxoplasma gondii

What disease does Toxoplasma gondii cause?

Toxoplasmosis

What two patient populations are at a significant risk if they develop Toxoplasmosis?

Fetus (via placenta) and AIDS pts

Which bodies of water are most associated with cryptosporidium? Why?

Contaminated drinking or recreational water due to its resistant to chlorine disinfection

Which organism causes cyclosporiasis?

Cyclospora cayetanensis

How soon do cyclosporiasis symptoms start after ingestion?

7 days