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19 - Pathology Fungi


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Fungi infections are common in these people
Diagnosis of fungi is based on ________
tissue culture
Opportunistic pathogens usually cause ______ infections
Superficial mycoses are limited to the ______ layer of the skin
Cutaneous mycoses are limited to the ______
Easiest way of classifying fungi
Anatomical location
Yeast are __1__-cellular which reproduce by __2__
1. uni-
2. budding
Molds are __1__-cellular __2__ colonies
1. multi-cellular
2. filamentous
Branching structures of molds
Fungi can exist as what two life forms

What are Dimorphic fungi
exist as both mold and yeast forms
the "fruiting body" characteristic of molds, which dissiminates "spores"
Name 2 opportunistic yeasts
Candida albicans

Cryptococcus Neoformans
Stool from a normal patient will usually contain what organisms?

Stool from a hospitalized patient on broad-spectrum antibiotics will have what organism in his stool?
Anaerobic bacteria

Candida (commensal)
Candida albicans usually appears with what kind of symptom?
Oral thrush
Complication of oral thrush
can spread to Esophagus and cause Dysphagia
Histology of Candida
budding yeast with Pseudohyphae
What can happen if a person is IC'ed and has thrush?
Thrush can invade blood vessels and disseminate

(rarely happens in normal host)
Fungus whose habitat is alkaline bird droppings
Cryptococcus Neoformans
Special structure on Cryptococcus Neoformans
Mucinous capsule that prevents drying and phagocytosis
Most common symptom of Cryptococcus Neoformans

*pneumonia may occur as well
Cryptococcus neoformans histologic appearance
-budding yeast with mucinous capsule
-narrow budding
Diagnosis of cryptococcus in normal hosts
Antigen testing of CSF
Diagnosis of cryptococcus in IC'ed hosts
India Ink Prep
Hyalohyphomycosis organism
Aspergillus histology
hyphae that branch at acute angles
Way to differentiate Hyalohyphomycoses species
3 clinical classifications of Aspergillosis
1. Allergic aspergillosis
2. Aspergilloma
3. Disseminated (invasive) Aspergillosis
Explain Allergic Aspergillosis
-Common in a asthmatics

-not an infection: spores are inhaled -> IgE response -> bronchospasm
Explain Aspergilloma
-NON-INVASIVE "fungus ball"
-occupies previous anatomical empty space such as sinus cavity or abscess
Describe Invasive Aspergillosis
In IC'ed host aspergillus invades lung tissue and bloodstream --> occludes vessels --> infarction
2 Most common Zygomycoses species
Rhizopus (most common)

Mucor (most commly known to docs)
Zygomycoses (Mucor) histo appearance
BROAD Hyphae that branch at RIGHT ANGLES
Zygomycosis usually affects this group of people
Commonly involved areas of Rhinocerebral Zygomycosis
Frontal Lobe
Systemic (deep) mycoses have this characteristic
Dimorphic = have both yeast and mycelial form

*only yeast form occurs within human
4 agents of Systemic (deep) Mycoses
1. Histoplasma capsulatum
2. Blastomyces Dermatitidus
3. Coccidiodes Immitus
4. Paracoccidioides brasiliensis
Agent most common in Ohio, Missouri, and Mississippi river valleys
Histoplasma capsulatum usually causes this
Self-limited Upper Respiratory tract infection

heals with Calcified granuloma similar to TB
Histoplasma may present as this in an IC'ed host
disseminated disease
Histology of Histoplasma
small, budding yeast at 37'C
within Macrophages
Histoplasma elicits _______ formation

*similar to TB
Found along the Mississippi and Ohio river valleys and Great Lakes
Blastomyces dermatitidus
-this leads to infectious aerosols
-primary route of infection
1. disturbance of SOIL by construction

2. respiratory tract
Histology of Blastomyces

-they usually form:

Rarest yet most severe of the Systemic fungal infections
Blastomyces dermatidis
Where is Coccidioides Immitus found geographically?
Desert SW
How may Coccidioides Immitus present? (3)
Skin rash
Erythema nodosum (red nodule)
Unique feature of Coccidioides
Arthroconidia = conidia which break off the mycelial hyphae and can be breathed in and are very infectious
Histologic appearance of Coccidioides Immitus
Spherules containing Endospores which provoke inflammatory rxn upon rupture
Coccidioides immitus can be mistaken for this
Toxoplasma gondii (coccidian parasite)
Paracoccidioides Brasiliensis is also know as _______________
South American Blastomycosis
Primary infection of Paracoccidioides
Histology of Paracoccidioides brasiliensis
Wagon wheel with knobs on outside
2 Filamentous Bacteria
Actinomyces israelii

Actinomyces israelii forms ____

Nocardia is a ________ organism
1. sulfur granules

2. weakly acid fast
Both nocardia and actinomyces are _______ bacteria
Gram +
4 distinct clinical syndromes of Actinomycosis
1. Cervical-facial = results from dental surgery

2. Thoracic = results from aspiration

3. Abdominal = following trauma or surgical disruption of bowel

4. Pelvic = associated with IUDs
Actinomycosis pathology:
-colonies are naked to the visible eye and present as __1__

-__2__ tracts are common, and may form __3__
1. Sulfur granules
2. sinus
3. cutaneous fistulas
Actinomyces commonly form a mass in the __1__ and may be mistaken for __2__
1. neck

2. malignant tumors

*called the "most misdiagnosed disease" for confusion with neoplasms
Nocardia asteroides are commonly found in the ______
Nocardia enters via __1__, resulting in pulmonary infections, which may form __2__ or __3__ that can be mistaken for TB or Carcinoma
1. soil -> Pulmonary route
2. broncho-pleural
3. cutaneous fistulas
Nocardia colony morphology
"molar tooth" appearance
How to differentiate Nocardia from Actinomycetes
Nocardia is weakly acid fast

(both are gram +)
Aspiration of Nocardia usually involved this part of lung
Right lower lobe
Pneumocystis carinii replicates in the human ____ with a life cycle that includes the formation of ______

Intra-alveolar cysts
PCP primarily infects the __________
Most of the population is infected with PCP by age ____
How is PCP infection acquired?
aerosolized mouse urine
HIV patients usually with this CD4 count require life-long chemo-prophylaxis to prevent PCP recrudescence
PCP Chest X-ray shows ____ pneumonia with a characteristic "______" appearance

PCP sputum examination may be diagnostic, but a ______ has a higher yield
Broncho-alveolar lavage
Can PCP be cultured?
nope, rely on special stains to make diagnosis

What fungus?
Pneumocystis carinii
PCP prevention doc: __1__
Inhaled ___2___ is sometimes used
1. Trimethoprim/Sulfamethoxazole (Bactrim)

2. Pentamidine

Candida with pseudohyphae

Special features?
Cryptococcus Neoformans
*pic on left is Meningitis
-bird droppings
-mucinous capsule
-narrow-base budding
-Antigen testing in normal
-India Ink in IC'ed

What is the arrow pointing at?

Aspergilla with acute (<45') hyphae branching

Aspergilla fumigatus

Aspergilla fumigatus

Rhinocerebral Zygomycosis

Fungus that causes this "coin lesion"

What cell are these fungi usually found in?
Histoplasma capsulatum

Macrophage (histiocytes)

What fungus?
Histoplasma capsulatum

These finding were found in an AIDS patient...what fungus?
Histoplasma capsulatum

Bone marrow: which is the best place for this fungus to grow

Fungus that divides by Broad-based budding
Blastomyces dermatitidis

Blastomyces dermatitidis
-broad based budding
-can mimic carcinoma

Fungus with Spherules containing endospores
Coccidioides immitus

(resembles Toxoplasma)

Paracoccidioides brasiliensis

Commonly forms fistulas
Actinomyces israelii
-sometimes can see Sulfur Granules

What fungus?
What stain is used?

acid fast

Commonly causes Pneumonia and Kidney/Brain abscesses

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