intruduction to fungi Flashcards

Question

how fungi cause disease?

Answer 1

1) invasion 2) hypersensitivity 3) toxins

Answer 2

Limited to outermost layers of skin, hair, nails and mucosa 1. Pityriasis Versicolor (pigmented lesions on the upper torso) 2. Dermatophytosis (Ringworm/tinea) 3. Candidiasis Diagnosis – skin scrapings (KOH - microscopy)

Answer 3

skin scrapings (KOH - microscopy)

Answer 4

A benign, superficial skin infection most commonly caused by the yeast species Malassezia furfur and Malassezia globosa. Particularly common in warm, humid climates and in individuals with hyperhidrosis. Presents with mildly pruritic, clearly demarcated macules with a fine-scale that become noticeably hypopigmented after exposure to the sun.

Answer 5

Pityriasis Versicolor a. Common – patchy rash b. Pale brown/pink macules - Pale patches more common in darker skin c. c. Itchy d. Trunk / Neck most common

Answer 6

a diagnostic test to examine skin lesions with a lamp that emits ultraviolet light. Used to evaluate hypopigmented or depigmented lesions (e.g., vitiligo) and superficial fungal infections of the skin (e.g., erythrasma), which appear characteristically fluorescent under ultraviolet light.

Answer 7

diagnostic test to examine skin lesions with a lamp that emits ultraviolet light. Used to evaluate hypopigmented or depigmented lesions (e.g., vitiligo) and superficial fungal infections of the skin (e.g., erythrasma), which appear characteristically fluorescent under ultraviolet light.

Answer 8

potassium hydroxide (KOH) preparation of skin scrapings demonstrates the "spaghetti and meatballs" pattern

Answer 9

``` • Topical: –azoles (ketoconazole) –Selenium sulfide • Oral azoles: –Fluconazole –Itraconazole ```

Answer 10

A group of fungal skin infections often caused by dermatophytes. It can affect a variety of areas of the body, including: feet (tinea pedis), nails (tinea unguium), scalp (tinea capitis), torso (tinea corporis) and groin (tinea cruris). Less commonly-affected areas include the face (tinea faciei), hands (tinea manuum), and beard (tinea barbae).

Answer 11

A dermatophyte infection that affects a body area other than the feet, scalp, nails, or groin. Manifests with erythematous, round, pruritic plaques with central clearing and raised borders (ringworm appearance).

Answer 12

o Trichophyton spp o Epidermophyton spp o Microsporum spp -affect keratinized tissue

Answer 13

A quick, inexpensive test to differentiate certain fungal infections (e.g., dermatophytes, Candida) from other skin disorders (e.g., eczema, psoriasis). A sample of the affected area is evaluated under a microscope after the addition of potassium hydroxide (KOH). KOH is a strong alkali that dissolves cells and protein debris in specimens but leaves fungal elements (e.g., budding yeasts, hyphae, spores, and pseudohyphae).

Answer 14

Sabouraud agar | A growth medium that contains dextrose and peptones. Used to culture dermatophytes and other fungi.

Answer 15

* Oral terbinafine | * Topical antifungals (terbinafine, clotrimazole) and keratolytic agents

Answer 16

inhibit fungal squalene epoxidase, which decreases ergosterol synthesis Adverse effects include taste disturbance, gastrointestinal upset, hepatotoxicity, and headaches.

Answer 17

• Involves deeper layers of the dermis and subcutaneous tissue •At sites of trauma – acquired from soil/thorns – Sporotrichosis – Sporothrix schenckii (dimorphic fungus)

Answer 18

Manifestations include localized skin lesions (e.g., pustules, ulcers, nodules) and ascending lymphangitis. It can become disseminated in patients who are immunocompromised. Gardeners are at risk

Answer 19

* Itraconazole | * Pulmonary or Disseminated disease = Amphotericin B

Answer 20

Bind to ergosterol in the fungal cell membrane forms pores that disrupt electrolyte balance

Answer 21

– Yeast (encapsulated) – Soil, avian faeces, rotting vegetation – Inhaled into lungs – generally no symptoms – Meningitis in immunosuppressed patients HIV – Organ transplant – Steroids – Malignancy

Answer 22

* Clinical suspicion * Antigen detection in blood & CSF * Microscopy (India-ink) rarely used now * Culture of CSF, blood * 18s PCR on tissue samples

Answer 23

• Grow as molds at 25°C, yeasts at 37°C • Not common in Ireland, UK or rest of Europe but found in North America • Found in soil • Guano from birds & bats • Caves! • May cause (clinically) 1)Asymptomatic infection 2)Acute/ chronic respiratory infection resembling TB 3)Disseminated, involving liver, lungs, spleen (immunosuppressed patients) • Fungus lives intracellular in macrophages => immune-evasion

Answer 24

in macrophages

Answer 25

A dimorphic fungus endemic to Latin America that causes paracoccidioidomycosis if its spores are inhaled. Forms large, budding yeast with a characteristic shape that resembles a captain's wheel. Cause skin and mucosal ulcers, granulomas

Answer 26

- -Acute pneumonia - -Painful nasal, pharyngeal, and laryngeal mucosal ulcerations - -Lymphadenopathy (usually cervical) - -Can disseminate → extrapulmonary manifestations (including verrucous skin lesions)

Answer 27

- Pseudo-yeasts, eg Candida albicans, C. tropicalis, etc - Part of the normal flora of mouth, intestine and lower genital tract - Opportunist pathogens, of increasing importance - Superficial & systemic infections

Answer 28

* Erythema, plaque-like lesions * Warm, moist areas, skin folds (axilla, groin, perineum, under breasts) - intertrigo * Itchy, red, macular rash

Answer 29

n inflammation if the skin that particularly affects skin folds (submammary, inguinal, interdigital). Typically manifests as white macerations on an erythematous base with satellite lesions and possibly scaling. Most commonly caused by infection with candida albicans. Aggravating factors include obesity, sweat, feces, urine, and vaginal discharge.

Answer 30

* Antibiotics * Steroids * Pregnancy * Immunosuppression

Answer 31

False | As there is a hypoestrogenic state

Answer 32

– Topical antifungal agents: Clotrimazole | – Oral: Fluconazole

Answer 33

localized, mucocutaneous Candida infection characterized by white plaques in the oral cavity that can be scraped off, giving way to red, inflamed, or bleeding areas. Other manifestations include a cottony feeling in the mouth, loss of taste, and in some cases, pain while eating. Thrush can be also 1)Oral 2)Vaginal 3)esophageal (esp. HIV)

Answer 34

``` – Antibiotic or steroid therapy – Immunosuppressed (HIV, chemo) – Transplant (SOT and BMT) – Post-operative – GI surgery – Intravenous catheters/indwelling devices – Diabetes mellitus/Burns – ICU – PN (parenteral nutrition) ```

Answer 35

– The major disease of immunocompromised hosts | – The fourth commonest cause of bloodstream infection in hospital patients

Answer 36

``` –• Specimens: – Blood, sterile site samples, tissue • Microscopy : – Budding yeasts – Gram-positive- large dark purple cells – Germ tube test • Culture: – Grow aerobically on blood and selective agar (Sabouraud dextrose agar, Chromogenic agar) • Identification - MALDI-TOF ```

Answer 37

A germ tube is an outgrowth produced by spores of spore-releasing fungi during germination. - -Candida spp. form yeast cells and pseudohyphae at 20–25°C - -Candida albicans forms germ tubes at 37°C

Answer 38

Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI TOF-MS) allows rapid and accurate identification of microorganisms.

Answer 39

albicans can take on either a unicellular (yeast) or multicellular (hyphae, pseudohyphae) form. The yeast form is 10-12 microns across and is Gram-positive.

Answer 40

• Mold/ filamentous fungus • Found in soil, air, plants and decomposing organic matter • Hospital environments: construction work • Spore-forming organism –Spores inhaled –Germinate to form hyphae –Destruct blood vessels & disseminate • Allergy due to the reaction to Aspergillus antigens in atopic individuals

Answer 41

1. Allergic aspergillosis - Sinusitis - Broncho pulmonary 2. Allergic bronchopulmonary aspergillosis (ABPA) 3. Aspergilloma 4. Invasive aspergillosis

Answer 42

Chronic exposure to Aspergillus can result in ABPA, presenting with asthmatic symptoms or sinusitis, especially in patients with a history of asthma or cystic fibrosis. It is primarily managed with glucocorticoid therapy.

Answer 43

True | • Eosinophilia, high IgE

Answer 44

* Diagnosis –high antibody titers in serum | * Fleeting CXR changes

Answer 45

* Bronchospasm, obstruction * Wheeze, cough, SOB, fever * Treat with steroids +/- itraconazole

Answer 46

A fungal mass in a pre-existing cavity that mainly affects the lungs and is visible on a chest X-ray as a "fungus ball" that moves on the repositioning of the patient. It is a form of chronic pulmonary aspergillosis. – Sputum positive in 66% – Antibodies positive in 70%

Answer 47

Asymptomatic, chronic cough, hemoptysis

Answer 48

``` – Prolonged neutropenia (> 14 days) e.g. AML – Transplantation – HIV – Diabetes mellitus – High dose steroids – Major surgery ```

Answer 49

– The primary site is lung – Macrophages/Neutrophils eradicate inhaled spores in immunocompetent – Widespread destructive growth in lung tissue – Invasion of blood vessels – Dissemination to other sites(liver, spleen, kidney, CNS) – Poor prognosis

Answer 50

The primary site is the lung

Answer 51

galactomannan test: Galactomannan antigen is a heteropolysaccharide component of the Aspergillus cell wall that is shed during the phase of hyphal growth.

Answer 52

,3-β-D glucan tests are nearly as sensitive as galactomannan antigen assays but have a low specificity because they can also be seen with invasive candidiasis.

Answer 53

• Opportunistic lung infection in immunosuppressed patients – HIV – Organ transplantation especially lung – Haematopoetic stem cell transplant – Corticosteroid treatment • Incidence has greatly declined since the introduction of prophylaxis

Answer 54

Methenamine silver A yeast-like fungus originally classified as a protozoan that causes Pneumocystis pneumonia. Identified as disc-shaped yeast form on methenamine silver stain of lung tissue.

Answer 55

Symptoms typically have a gradual onset (days to weeks) and include: -Low-grade fever and malaise -Dyspnea and non-productive cough -Fatigue, weight loss, chills May progress to fulminant respiratory failure Can be asymptomatic

Answer 56

If PCP is suspected based on the history and clinical examination, oxygen saturation, the CD4+ count, the beta-D-glucan level should be measured and a CXR conducted. If the CXR is inconclusive, a high-resolution CT scan can be obtained. The diagnosis should generally be confirmed via microscopic identification of P. jirovecii from respiratory secretions.

Answer 57

1) Chest X‑ray - -Typically symmetrical, diffuse interstitial infiltrates extending from the perihilar region, ground glass infiltrates - -May sometimes be normal 2) High-resolution CT - -Indicated if PCP is still suspected in a patient with a normal CXR - -High sensitivity for PCP; a negative scan thus suggests the diagnosis of PCP is unlikely

Answer 58

microscopic identification of P. jirovecii in a specimen obtained via bronchoalveolar lavage or induced sputum, with methenamine silver staining and immunofluorescence Staining enables visualization of disc-shaped P. jirovecii cysts with central spores these cysts resemble “crushed ping-pong balls” with central “dots”.