Ch 27 Flashcards
(157 cards)
1
Q
What are hyphae in fungal morphology?
A
Hyphae are filamentous cellular units of molds and mushrooms.
2
Q
What is the key feature of nonseptate (coenocytic) hyphae?
A
They lack cross walls, have irregular width, and branch at broad angles.
3
Q
What is the appearance of nonseptate hyphae under the microscope?
A
They appear broad, with uneven width and no internal divisions (cross walls).
4
Q
How do septate hyphae differ from nonseptate hyphae?
A
Septate hyphae have cross walls (septa) and a regular tube-like shape.
5
Q
Which type of hyphae shows fairly regular width and tube-like structure?
A
Septate hyphae.
6
Q
Do mushrooms have hyphae? If so, what type?
A
Yes, mushrooms have hyphae, typically septate.
7
Q
What is the significance of septa in hyphae?
A
Septa divide the hyphae into individual cells and help in cellular organization and damage control.
8
Q
What are dimorphic fungi?
A
Dimorphic fungi can convert from hyphal to yeast (or yeast-like) forms depending on temperature.
9
Q
What does “thermally dimorphic” mean?
A
It means the fungus exists as a mold at low temperatures (25°C) and as a yeast at body temperature (37°C).
10
Q
What is the phrase used to remember thermal dimorphism?
A
“Mold in the cold, yeast in the beast.”
11
Q
Name five key thermally dimorphic fungi.
A
Blastomyces, Coccidioides, Histoplasma, Paracoccidioides, Sporothrix.
12
Q
Which fungus forms pseudohyphae?
A
Candida albicans.
13
Q
What are pseudohyphae?
A
They are elongated yeast cells with constrictions at each septum, resembling hyphae.
14
Q
How do pseudohyphae differ from true hyphae?
A
Pseudohyphae have constrictions at the septa, while true hyphae are uniform and tubular.
15
Q
What is the purpose of KOH (10%) wet mount in fungal diagnosis?
A
KOH dissolves human tissue, leaving fungal elements like hyphae and yeast visible.
16
Q
How is the KOH wet mount prepared?
A
Heat gently, let sit for 10 minutes before observation.
17
Q
What is detected using India ink stain?
A
Cryptococcus neoformans – shows a clear halo due to its capsule in CSF samples.
18
Q
What does the Periodic acid-Schiff (PAS) stain detect?
A
PAS highlights fungal cell walls in pink or magenta, useful for identifying fungi in tissues.
19
Q
What is the role of Calcofluor white stain?
A
It binds to chitin in fungal cell walls and fluoresces under UV light using a fluorescent microscope.
20
Q
Which stain requires a fluorescent microscope for observation?
A
Calcofluor white.
21
Q
Which fungal element becomes visible under India ink but not with KOH?
A
The capsule of Cryptococcus neoformans.
22
Q
What culture media are commonly used to grow fungi?
A
Sabouraud agar and blood agar with antibiotics.
23
Q
Which antibiotics are added to fungal culture media and why?
A
• Chloramphenicol: Inhibits bacteria.
• Cycloheximide: Inhibits contaminant fungi.
24
Q
How long does fungal culture typically take?
A
Several weeks.
25
What does fungal culture help identify?
Fungal morphology; sometimes used with PCR and nucleic acid probes for identification.
26
What is the purpose of serology in fungal diagnosis?
To detect the patient’s antibody response using tests like antibody screening and complement fixation.
27
What does antigen detection target in fungal diagnosis?
Fungal antigens in CSF or serum.
28
How is cryptococcal antigen commonly detected?
Using latex agglutination or counter immunoelectrophoresis.
29
What is the role of skin testing in fungal diagnosis?
Used for epidemiology or detecting anergy; it indicates prior exposure, not active infection.
30
What type of fungus is Malassezia furfur?
A lipophilic yeast that is part of the normal skin flora.
31
What condition does Malassezia furfur cause?
Pityriasis (Tinea) versicolor.
32
What are the clinical features of Pityriasis versicolor?
• Hypopigmented or hyperpigmented spots on the chest/back.
• Common in warm, moist climates.
• Often described as a “blotchy suntan.”
33
How does Malassezia furfur appear on KOH preparation?
Like “spaghetti and meatballs” – a mix of yeast cells and short hyphae.
34
What is seen under Wood lamp in Malassezia furfur infection?
Copper-orange fluorescence.
35
What is the treatment for Pityriasis versicolor?
Topical selenium sulfide or azole antifungals.
36
What severe condition can Malassezia furfur cause in premature infants?
Fungemia, especially in those receiving IV lipid therapy.
37
What are the two types of cutaneous fungal infections?
Yeast infections (Candidiasis) and Dermatophyte infections.
38
What areas can Candida infect in cutaneous or mucocutaneous infections?
Skin and mucous membranes.
39
Can Candidiasis disseminate? If yes, in whom?
Yes, it may disseminate in immunocompromised patients.
40
What type of fungi are dermatophytes?
Filamentous fungi (molds).
41
What tissues do dermatophytes infect?
Skin, hair, and nails.
42
Do dermatophytes disseminate systemically?
No, they do not disseminate.
43
Are dermatophytes monomorphic or dimorphic?
Monomorphic.
44
Which dermatophyte genus infects skin, hair, and nails?
Trichophyton.
45
Which dermatophyte genus infects only hair and skin?
Microsporum.
46
Which dermatophyte genus infects only skin and nails?
Epidermophyton.
47
What is another name for dermatophytic infections?
Tineas or ringworm.
48
What is Tinea capitis?
Ringworm of the scalp; the most serious form is favus, which is highly contagious and can cause permanent hair loss.
49
What is Tinea barbae?
Ringworm of the bearded area (face and neck).
50
What is Tinea corporis?
Dermatophyte infection of the glabrous (smooth, hairless) skin of the body.
51
What is Tinea faciei?
Ringworm infection of the face.
52
What is Tinea cruris?
Also called jock itch; affects the groin area.
53
What is Tinea pedis?
Also called athlete’s foot; affects the feet, especially between the toes.
54
What is Tinea manuum?
Dermatophyte infection of the hand.
55
What is Tinea unguium (Onychomycosis)?
Fungal infection of the nails.
56
What is a kerion?
An inflammatory abscess-like reaction associated with Tinea capitis, faciei, or corporis.
57
What is an ID reaction (Dermatophytid)?
An allergic response to circulating fungal antigens, not a direct fungal infection.
58
What is the most common symptom of dermatophytic infections?
Itching.
59
What type of dermatophyte usually causes high inflammation?
Zoophilic fungi (from animals).
60
What type of dermatophyte usually causes low inflammation?
Anthropophilic fungi (from humans).
61
Which dermatophyte genus fluoresces under Wood lamp?
Microsporum shows bright yellow-green fluorescence.
62
What is seen on KOH mount in dermatophytic infections?
Arthroconidia and hyphae.
63
What are the topical treatments for dermatophyte infections?
Imidazole or tolnaftate.
64
What are the classical thermally dimorphic fungi that cause systemic infections?
Histoplasma, Coccidioides, Blastomyces, Paracoccidioides.
65
What does “thermally dimorphic” mean for systemic fungal pathogens?
They grow as molds at 25°C and as yeasts at 37°C.
66
What are the common clinical features of systemic fungal infections?
• Acute pulmonary infections (often asymptomatic or self-limiting).
• May progress to chronic pulmonary or disseminated disease.
67
What percentage of acute pulmonary fungal infections are self-resolving?
Approximately 95%.
68
What stain is used in sputum cytology for detecting fungi?
Calcofluor white stain.
69
What culture media are used for systemic fungal pathogens?
Blood agar, Sabouraud agar, and inhibitory mold agar.
70
Which systemic fungal pathogen is especially detected via peripheral blood culture?
Histoplasma (due to reticuloendothelial system involvement).
71
Where is Histoplasma capsulatum commonly found in the environment?
In soil enriched with bird or bat droppings.
72
What activities increase the risk of exposure to Histoplasma capsulatum?
Spelunking, cleaning chicken coops, and bulldozing bird roosts.
73
What is the environmental (mold) form of Histoplasma capsulatum?
Hyphae with microconidia and tuberculate macroconidia.
74
What is the tissue form of Histoplasma capsulatum?
Small intracellular yeast (no capsule) with narrow-neck budding.
هذا الوصف ينطبق على فطر اسمه Histoplasma capsulatum في شكله داخل الجسم:
• لما يدخل جسم الإنسان، بصير خميرة صغيرة
• بتعيش داخل الماكروفاج
• ما إلها كبسولة
• وتتكاثر بطريقة اسمها narrow-neck budding
⸻
75
Where does Histoplasma capsulatum reside in human tissues?
Inside macrophages (Reticuloendothelial system – RES).
76
What is the typical disease presentation of Histoplasma infection?
“Fungus flu” – acute or asymptomatic pneumonia with flu-like symptoms and possible hepatosplenomegaly.
77
What are signs of disseminated histoplasmosis?
Mucocutaneous lesions, calcified lesions, common in AIDS patients, may relapse with T-cell suppression.
78
What diagnostic methods are used for Histoplasma?
Sputum cytology/culture; peripheral blood culture for RES involvement.
79
What is the environmental form of Coccidioides immitis?
Hyphae that fragment into arthroconidia, which are inhaled.
80
What is the tissue form of Coccidioides immitis?
Spherules filled with endospores.
81
What disease is caused by Coccidioides immitis?
Valley Fever (Coccidioidomycosis).
82
What are the common clinical features of Valley Fever?
• Asymptomatic or acute pneumonia
• Desert bumps (erythema nodosum)
• Arthritis
• Possible calcified pulmonary lesions
83
Who is at higher risk of disseminated coccidioidomycosis?
People with AIDS and pregnant women (especially in the 3rd trimester).
84
What is the treatment for mild to moderate coccidioidomycosis?
Itraconazole.
85
What is the treatment for severe or systemic coccidioidomycosis?
Amphotericin B.
86
What is the environmental form of Blastomyces dermatitidis?
Hyphae with nondescript conidia, often found in rotting wood and soil.
87
What is the tissue form of Blastomyces dermatitidis?
Broad-based budding yeast with a thick, double-refractile wall.
88
What types of diseases can Blastomyces dermatitidis cause?
• Acute and chronic pulmonary disease (less likely to self-resolve)
• Disseminated disease is also possible.
89
How does pulmonary blastomycosis usually present?
As a non-resolving pneumonia that can become chronic or disseminated.
90
What is the environmental form of Paracoccidioides brasiliensis?
Septate hyphae with chlamydoconidia, found in humid, vegetative, acidic soils.
91
What is the tissue form of Paracoccidioides brasiliensis?
Yeast with multiple buds, showing a classic “pilot wheel” appearance.
92
What disease is caused by Paracoccidioides brasiliensis?
Paracoccidioidomycosis.
93
What are the features of the juvenile form of paracoccidioidomycosis?
Flu-like symptoms, lymphadenopathy, hepatosplenomegaly, and skin lesions.
94
What are the features of the adult form of paracoccidioidomycosis?
Pulmonary fibrosis, bullae formation, and oral/cutaneous lesions.
95
What type of fungus is Aspergillus fumigatus?
A monomorphic filamentous fungus with dichotomous branching.
96
What is a fungus ball (aspergilloma)?
A mass of fungal hyphae that grows freely in preformed lung cavities; may require surgical removal to prevent coughing and pulmonary hemorrhage.
97
What is invasive aspergillosis and who is at risk?
A serious tissue-invasive infection seen in patients with severe neutropenia, chronic granulomatous disease (CGD), cystic fibrosis, and burns.
98
How does invasive aspergillosis affect tissues?
It invades blood vessels, causing infarcts and hemorrhage.
99
What are other manifestations of aspergillosis?
• Nasal colonization, which may lead to pneumonia or meningitis
• Cellulitis in burn patients
• Dissemination in immunocompromised hosts
100
What is ABPA and who is predisposed to it?
Allergic bronchopulmonary aspergillosis, occurs in asthma and cystic fibrosis patients due to fungal growth in mucous plugs without tissue invasion.
101
What is the treatment for invasive aspergillosis and aspergilloma?
Voriconazole.
102
What is the treatment for ABPA?
Glucocorticoids and itraconazole.
103
Where is Candida albicans normally found?
It is a yeast that is part of the normal mucous membrane flora.
104
Which Candida species account for ~90% of bloodstream infections?
C. albicans, C. glabrata, C. parapsilosis, and C. tropicalis.
105
What test helps identify C. albicans?
Germ tube test – C. albicans forms germ tubes at 37°C in serum.
106
How does C. albicans appear when invading tissue?
It forms pseudohyphae and true hyphae (unlike non-pathogenic Candida).
107
What is Perlèche and what causes it?
Cracks at the corners of the mouth, often due to malnutrition.
108
What are common causes of oral thrush?
Prematurity, antibiotics, immunocompromised states (e.g., AIDS).
109
What are risk factors for esophageal and gastric candidiasis?
Antibiotic use and immunosuppression (e.g., AIDS).
110
Who is at risk for Candida septicemia?
Immunocompromised, cancer patients, and those with IV lines; may lead to endophthalmitis and skin lesions.
111
What group is at risk of Candida endocarditis?
Intravenous drug abusers, often following transient candidemia.
112
Who is at risk for cutaneous Candida infections?
Obese individuals, infants, and those who wear rubber gloves.
113
Who is prone to yeast vaginitis due to Candida?
Diabetic women.
114
What is chronic mucocutaneous candidiasis?
A condition with endocrine defects and anergy to Candida, leading to chronic infection of skin, nails, and mucous membranes.
115
What are the primary commensal sites of Candida in the human body?
• Oral cavity
• Gastrointestinal tract
• Genital tract
116
What disease does Candida cause in the oral cavity?
Oropharyngeal Candidiasis (acute, chronic, or chronic-mucocutaneous).
117
What are the predisposing factors for oropharyngeal candidiasis?
• Broad-spectrum antibiotics
• Dysfunctional T-cell immunity
• Nutritional deficiencies
• Salivary hypo-function
• Smoking
• Wearing dentures
118
How does Candida cause systemic candidiasis?
Through translocation across damaged gut mucosa into the bloodstream.
119
What are the risk factors for systemic candidiasis?
• Gut mucosa damage (e.g., surgery)
• Broad-spectrum antibiotics
• Immunosuppression
• Central venous catheter
• Lengthy ICU stays
• Dialysis
120
What percentage of women experience vulvovaginal candidiasis?
75% experience at least one episode in their life, and 5% have recurrent episodes.
121
What are the predisposing factors for vulvovaginal candidiasis?
• High estrogen levels
• Use of oral contraceptives
• Diabetes
122
What is mucocutaneous candidiasis?
A form of Candida infection that affects skin and mucous membranes, often due to underlying immune defects.
123
What microscopic forms can be seen in Candida diagnosis using KOH prep?
Pseudohyphae, true hyphae, and budding yeasts.
124
What is the germ tube test used for?
To identify Candida albicans by detecting germ tube formation in horse serum at 37°C.
125
What is a positive germ tube test result?
A continuous filament growing from the yeast cell without constriction at the point of attachment.
126
How is Candida septicemia diagnosed?
Through blood cultures and biochemical identification (including germ tube test).
127
What are treatment options for localized Candida infections?
Topical or oral imidazole, nystatin.
128
Why is Candida auris a serious global health threat?
1. Often multidrug-resistant
2. Difficult to identify with standard lab methods
3. Responsible for healthcare-associated outbreaks
129
Why is misidentification of Candida auris dangerous?
It may lead to inappropriate treatment and failure to apply infection control measures.
130
What should healthcare facilities do if Candida auris is suspected?
Quickly identify the fungus and implement special infection control precautions to stop its spread.
131
What type of organism is Cryptococcus neoformans?
It is an encapsulated, monomorphic yeast.
132
Where is Cryptococcus neoformans found in the environment?
In soil enriched with pigeon droppings.
133
What diseases are caused by Cryptococcus neoformans?
• Meningitis, especially in AIDS and Hodgkin’s disease patients
• Acute pulmonary infections, often asymptomatic, especially in pigeon breeders
134
What is the main diagnostic sample used to detect cryptococcal meningitis?
Cerebrospinal fluid (CSF).
135
How is the capsule of Cryptococcus neoformans detected in CSF?
By latex agglutination or counter immunoelectrophoresis to detect capsular antigen.
136
What does India ink staining show in Cryptococcus infection?
Budding yeasts with capsular halos (though it misses about 50% of cases).
137
What is seen in culture of Cryptococcus neoformans?
Urease-positive yeast.
138
What is the initial treatment for cryptococcal meningitis?
Amphotericin B + Flucytosine (5FC) for at least 10 weeks (until afebrile and culture-negative).
139
What type of fungi are Mucor, Rhizopus, and Absidia?
They are nonseptate filamentous fungi from the Zygomycophyta group.
140
Where are Zygomycophyta fungi found in the environment?
In soil; sporangiospores are inhaled.
141
How do Zygomycophyta fungi spread in the body?
They invade tissues aggressively, crossing anatomical barriers—especially from sinuses to the brain.
142
What is rhinocerebral zygomycosis and what causes it?
A severe fungal infection of the sinuses and brain, typically caused by Mucor or related fungi.
143
What are clinical features of rhinocerebral mucormycosis?
• Paranasal swelling
• Necrotic tissue
• Hemorrhagic exudate from nose/eyes
• Mental lethargy
144
Who is most at risk for mucormycosis?
Ketoacidotic diabetic patients and those with leukemia.
145
How is mucormycosis diagnosed microscopically?
KOH mount shows broad, ribbon-like nonseptate hyphae with ~90° branching.
146
Why is mucormycosis highly fatal?
Due to rapid fungal growth and aggressive tissue invasion.
147
What is Pneumocystis jirovecii classified as?
A fungus, identified based on molecular techniques like ribotyping.
148
Is Pneumocystis jirovecii intracellular or extracellular?
It is an obligate extracellular parasite.
149
How is Pneumocystis jirovecii visualized in tissues?
By silver stain, which highlights cysts in tissue samples.
150
What disease is caused by Pneumocystis jirovecii?
Interstitial pneumonia (also known as Pneumocystis pneumonia – PCP).
151
Who is most at risk for PCP (Pneumocystis pneumonia)?
• AIDS patients (especially with CD4+ count < 200/mm³)
• Malnourished infants
• Premature neonates
• Other immunocompromised individuals
152
What are typical symptoms of PCP?
Fever, cough, shortness of breath; usually nonproductive sputum except in smokers.
153
What is the appearance of lung exudate on H&E and silver stain?
• H&E: Foamy/honeycomb exudate
• Silver stain: Shows cysts and trophozoites that do not stain with H&E
154
What is the typical chest X-ray finding in PCP?
Patchy infiltrates with a ground-glass appearance; often spares lower lobe periphery.
155
How is PCP diagnosed?
By identifying silver-stained cysts in bronchial alveolar lavage (BAL) fluid or biopsy.
156
What is the treatment for mild PCP?
Trimethoprim/sulfamethoxazole (TMP-SMX).
157
What is used for treating moderate to severe PCP?
Dapsone, or high-dose TMP-SMX, sometimes with steroids in severe cases.
