END - Micro Flashcards

Question

25. From the following features which does not describe a "fungus ball"? a. Very invasive b. caused by aspergillus c. occupies an abnormal pulmonary space d. Also called aspergilloma

Answer 1

a. Very invasive. Rationale: A "fungus ball" or aspergilloma is typically non-invasive. It is a mass composed of fungal hyphae growing in a pre-existing cavity in the lung, not invading surrounding tissues.

Answer 2

c. griseofulvin. Rationale: Griseofulvin is an oral antifungal medication that accumulates in the stratum corneum of the skin. It is particularly used for treating infections of the skin, hair, and nails caused by dermatophytes.

Answer 3

b. Microsporum

Answer 4

c. griseofulvin. Rationale: Griseofulvin is an oral antifungal medication that accumulates in the stratum corneum of the skin. It is particularly used for treating infections of the skin, hair, and nails caused by dermatophytes.

Answer 5

c. intracellular. Rationale: Histoplasma capsulatum is primarily intracellular, residing within macrophages after infection. It does not form broad-based buds or spherules and is not encapsulated.

Answer 6

b. Menopause. Rationale: Menopause is generally not considered a predisposing factor for candidiasis vaginitis. The other options, including diabetes, broad-spectrum antibacterial chemotherapy, and pregnancy, are known to predispose women to this infection due to altered local immune defense and changes in the vaginal pH and flora.

Answer 7

b. peanuts. Rationale: Aflatoxin, produced by Aspergillus flavus (and also Aspergillus parasiticus), most notably contaminates peanuts, as well as corn and other nuts. However, peanuts are particularly prone to contamination under conditions of high humidity and temperature, which are conducive to the growth of these fungi.

Answer 8

b. Dermatophytosis. Rationale: The presence of branching, septate, nonpigmented hyphae in a skin scraping is indicative of a dermatophyte infection, or dermatophytosis. These fungi affect keratinized tissues (such as skin, hair, and nails) and typically present with circular, dry, scaly, and itchy lesions.

Answer 9

b. Pigeon droppings. Rationale: Cryptococcus neoformans is commonly associated with pigeon droppings, which provide a rich environment for the fungus to thrive. The birds themselves are not affected by the fungus but can carry large amounts of it in their droppings, increasing the risk of human exposure, especially in urban areas.

Answer 10

A. Penicillium marneffei is a dimorphic fungus. Rationale: Penicillium marneffei (now known as Talaromyces marneffei) is indeed a dimorphic fungus, meaning it can exist in both yeast and mold forms, depending on the temperature and environment. This characteristic is crucial for its identification and understanding its pathogenic mechanism.

Answer 11

a. Trichophyton tonsurans. Rationale: Trichophyton tonsurans is a common cause of "black dot" tinea capitis, which is characterized by the presence of dark spots within hair shafts on the scalp due to the hair breaking off at the scalp surface.

Answer 12

b. Eumycetoma and Actinomycetoma. Rationale: This question seems to focus on the appropriate treatments for both fungal and bacterial forms of mycetoma. Eumycetoma is caused by fungi and can be treated with antifungal medications like ketoconazole, itraconazole, and amphotericin B. Actinomycetoma, on the other hand, is caused by actinomycetes (a type of filamentous bacteria), and while traditionally treated with antibacterial agents, some of the treatments for fungal infections (like ketoconazole for secondary fungal infections or mixed infections) might be considered in certain cases.

Answer 13

c. Fungi have one or more nuclei and chromosomes. Rationale: Fungi are eukaryotic organisms, meaning they have a complex cellular structure with a nucleus containing chromosomes. They are not photosynthetic, they contain mitochondria, and not all fungi are anaerobic.

Answer 14

c. Histoplasmosis. Rationale: The description of intracellular yeast cells within macrophages and other myelogenous cells is characteristic of Histoplasma capsulatum, the causative agent of histoplasmosis. This fungus can cause systemic infections and is known to affect the bone marrow among other organs.

Answer 15

c. Multiple budding

Answer 16

d. saprophytic. Rationale: "Achlorophyllous" implies that the fungus lacks chlorophyll, the pigment necessary for photosynthesis. This means the fungus does not derive its energy from light but rather from decomposing organic material, classifying it as saprophytic.

Answer 17

a. Molds produce hyphae that may or may not be partitioned with cross-walls or septa. Rationale: This statement is correct as molds can produce both septate (with cross-walls) and aseptate (without cross-walls) hyphae, depending on the species. The other options contain inaccuracies: yeasts do have cell walls, not all yeasts produce pseudohyphae, and conidia are typically products of asexual reproduction.

Answer 18

b. Epidermophyton

Answer 19

B. In a form that is minimally encapsulated. Rationale: For Cryptococcus neoformans, being minimally encapsulated when inhaled facilitates entry into the lungs and establishment of infection, as the minimal capsule allows for better evasion of immune detection during initial colonization.

Answer 20

d. diabetes. Rationale: While Aspergillus infections can occur in individuals with diabetes, it is less likely compared to those with cancer or impaired immune systems, or those with calcified TB lesions, where the fungus finds an easier niche to colonize or immunocompromised conditions that allow for invasive infection.

Answer 21

a. Eumycetoma. Rationale: Eumycetoma is characterized by the presence of granules containing large hyphal fragments within the discharge or infected tissues. Actinomycetoma, caused by bacterial agents, typically shows granules with filamentous bacteria.

Answer 22

d. Pneumocystis jiroveci. Rationale: Pneumocystis jiroveci is the causative agent of Pneumocystis pneumonia in HIV/AIDS patients, not Penicillium marneffei, which causes penicilliosis.

Answer 23

b. Cryptococcus neoformans. Rationale: Cryptococcus neoformans is known for its thick gelatinous capsule, which is a major virulence factor and diagnostic feature, particularly visible using India ink staining.

Answer 24

C. thrush. Rationale: Thrush is caused by Candida spp., not Aspergillus fumigatus. Aspergillus can cause tissue invasion, aspergilloma, and allergic reactions but not thrush.

Answer 25

b. Plants. Rationale: Dermatophytes are fungi specialized in infecting keratinized tissues of humans, animals, and soil but are not typically associated with plants.

Answer 26

c. Candidiasis and dermatophytosis. Rationale: Candidiasis and dermatophytosis are among the most common fungal infections and part of normal human biota. Candidiasis involves yeast from the Candida genus, and dermatophytosis involves skin infections by dermatophytes. These conditions are prevalent and often involve organisms that are common in the human environment.

Answer 27

b. Actinomycetoma Rationale: Actinomycetoma is characterized by granules containing fine filaments typical of the actinomycetes (bacterial origin), while eumycetoma (fungal origin) granules contain larger fungal hyphae.

Answer 28

b. Sabouraud's agar Rationale: Sabouraud's agar is the most common medium used for culturing fungi due to its low pH which inhibits bacterial growth, allowing for better fungal isolation and growth.

Answer 29

b. Microsporum and Trichophyton tonsurans Rationale: Both Microsporum and Trichophyton species are common etiologic agents of tinea capitis, affecting the scalp and hair of primarily children.

Answer 30

c. Aspergillosis Rationale: The presence of dichotomous branching hyphae in sputum is a hallmark of Aspergillus species. This finding in a heart transplant patient suggests a probable infection with Aspergillosis, particularly in the setting of immunosuppression.

Answer 31

b. Cigar-shaped

Answer 32

d. Fungal cell wall components are targets for major classes of antifungal antibiotics, such as polyenes and azoles Rationale: The fungal cell wall is a crucial target for many antifungal drugs. Polyenes, like amphotericin B, bind to ergosterol in the cell wall, disrupting membrane integrity, while azoles inhibit ergosterol synthesis.

Answer 33

B. Genital organs Rationale: Mycotoxins generally affect the liver, kidneys, and nervous system due to their roles in detoxification and susceptibility to toxin accumulation. The genital organs are typically less affected by mycotoxins compared to these other organ systems.

Answer 34

d. The pigments are not associated with virulence Rationale: This statement is inaccurate. In dematiaceous fungi, which are melanized fungi, the melanin within the cell wall is indeed associated with increased virulence, protecting the fungi from environmental stresses and immune responses.

Answer 35

c. Encapsulated Rationale: Cryptococcus neoformans is well-known for its thick polysaccharide capsule, which is a major virulence factor, helping the fungus evade immune detection.

Answer 36

d. Fungal cell wall components are targets for major classes of antifungal antibiotics, such as polyenes and azoles Rationale: As previously stated, the fungal cell wall is a critical target for antifungal therapies. Polyenes disrupt the fungal membrane by binding to ergosterol, while azoles inhibit ergosterol synthesis, thereby compromising the integrity and function of the fungal cell wall.

Answer 37

a. Microsporum Rationale: Infections caused by Microsporum species are known to cause hair fluorescence under Wood's lamp examination. This is a diagnostic feature not typically associated with Trichophyton tonsurans.

Answer 38

a. Elicit acute infections Rationale: Anthropophilic dermatophytes, which are adapted to humans, generally cause chronic, not acute, infections that are typically less inflammatory compared to those caused by zoophilic or geophilic dermatophytes.

Answer 39

a. Tinea capitis Rationale: Tinea capitis, or scalp ringworm, presents with circular bald patches and short broken hair stubs within the hair follicles, consistent with the description given.

Answer 40

c. Mycetoma Rationale: Mycetoma is a chronic subcutaneous infection characterized by swelling, sinus tracts, and the presence of granules in discharge, which can be caused by a variety of fungi and bacteria.

Answer 41

b. None of the choices Rationale: Neither Epidermophyton nor Microsporum infects blood vessels of the skin. These fungi are dermatophytes that infect keratinized tissues like the skin, hair, and nails but do not invade blood vessels.

Answer 42

d. Are inversely correlated with the CD4 lymphocyte count Rationale: In HIV/AIDS patients, the susceptibility to opportunistic fungal infections increases as the CD4 lymphocyte count decreases. This inverse relationship highlights the increased risk as the immune system becomes more compromised.

Answer 43

b. Traumatic implantation Rationale: Subcutaneous mycoses typically occur when fungi, which are often soil saprophytes, are introduced into the skin through traumatic implantation, such as through a puncture wound or other forms of direct inoculation.

Answer 44

B. Selenium sulfide Rationale: Inhibitory mold agar generally contains antimicrobial agents like cycloheximide, gentamicin, and chloramphenicol to suppress bacterial growth and select for fungi. Selenium sulfide is not commonly used in these media.

Answer 45

c. Confined to keratinized tissues Rationale: Infections caused by dermatophytes are confined to keratinized tissues such as the skin, hair, and nails because these fungi utilize keratin as a nutrient source. These infections are not easily treated with penicillin (which targets bacterial cell walls), are not associated with aflatoxin production or effects, and can indeed be associated with chronic lesions.

Answer 46

C. Arthroconidia Rationale: Arthroconidia result from the fragmentation of hyphal cells, which then develop into thick-walled, durable spores. This is a common reproductive strategy among certain fungi, including some dermatophytes and dimorphic fungi.

Answer 47

a. Phaeohyphomycosis may exhibit several clinical manifestations, including subcutaneous disease, brain abscess as well as sinusitis. Rationale: Phaeohyphomycosis is caused by various dematiaceous fungi and can present with a range of clinical manifestations from superficial to deep infections, including subcutaneous cysts, sinusitis, and even brain abscesses, particularly in immunocompromised patients.

Answer 48

c. Pityriasis versicolor. Rationale: The description of hypopigmented, non-pruritic, painless patches with branny desquamation fits the classic presentation of pityriasis versicolor, a superficial fungal infection caused by Malassezia species.

Answer 49

c. Culturing for fungi. Rationale: If bacterial pathogens are not isolated and antibiotics have failed, considering fungal causes is a logical next step, especially in cases with clinical presentations that could suggest fungal infections such as persistent pneumonia.

Answer 50

a. Mycetoma. Rationale: Mycetoma, which can be caused by both bacteria (actinomycetoma) and fungi (eumycotic mycetoma), is a deep, chronic infection typically involving the skin, subcutaneous tissue, and bones. It is not classified as a superficial mycosis.

Answer 51

a. Mycetoma. Rationale: Mycetoma, which can be caused by both bacteria (actinomycetoma) and fungi (eumycotic mycetoma), is a deep, chronic infection typically involving the skin, subcutaneous tissue, and bones. It is not classified as a superficial mycosis.

Answer 52

d. Blood. Rationale: Candida species are commonly isolated from mucous membranes and the skin as part of the normal flora and can colonize the gastrointestinal tract, but they are not normally found in the blood. Candidemia or the presence of Candida in the blood indicates an invasive infection, especially in immunocompromised individuals.

Answer 53

B. Mycelium. Rationale: A mass of fungal elements, consisting of intertwined hyphae, is called a mycelium. This is a basic structural unit of a fungus.

Answer 54

a. Both actinomycetoma and eumycotic mycetoma. Rationale: Both types of mycetoma (actinomycetoma caused by bacteria and eumycotic mycetoma caused by fungi) can form tightly-packed masses of filaments (mycelium in fungi and bacterial filaments in actinomycetoma) surrounded by a granulomatous rind.

Answer 55

b. Meningitis due to species of Candida would be confirmed by microscopic observation of oval yeast cells and pseudohyphae in the CSF. Rationale: The presence of yeast cells and pseudohyphae in CSF is indicative of Candida infection. Cryptococcal meningitis would be confirmed by detection of cryptococcal antigen in the CSF, not coccidioidin.

Answer 56

c. Phialoconidia. Rationale: Phialoconidia are conidia that are produced from a phialide, which is a type of conidiogenous cell that can be described as vase-shaped. This type of asexual spore production is characteristic of certain fungi, particularly in the Aspergillus genus.

Answer 57

c. The etiologic agent is dimorphic fungus Rationale: Sporothrix schenckii, the fungus causing sporotrichosis, is a dimorphic fungus, meaning it can exist as yeast at body temperature and as mold at lower temperatures. This is a fundamental aspect of its biology.

Answer 58

b. Trichophyton tonsurans Rationale: Trichophyton tonsurans is known for producing spores within the hair shaft (endothrix infection), typical of its infection pattern in tinea capitis.

Answer 59

c. Trichophyton Rationale: Trichophyton species infect the skin, hair, and nails, encompassing a wide range of dermatophytic infections.

Answer 60

b. Confinement in a "sick building" Rationale: Management of fungal hypersensitivity reactions includes avoiding the offending agent, possibly using corticosteroids to manage symptoms, and desensitization. Confinement in a "sick building" is not a management strategy and could potentially worsen symptoms if the building has mold issues.

Answer 61

d. Tinea pedis Rationale: The description of acute itching, red vesicular lesions, and chronic scaling fissures in the interdigital spaces of the feet is characteristic of tinea pedis, or athlete's foot.

Answer 62

a. Persistent cough in patient with lung CA Rationale: Persistent cough in a patient with lung cancer alone is not a criterion for administering antifungal prophylaxis unless accompanied by other specific risk factors or indications of fungal infection.

Answer 63

b. Tinea barbae Rationale: Tinea barbae is a fungal infection involving the beard area, typically presenting with edematous, erythematous lesions.

Answer 64

c. Multiple budding Rationale: Paracoccidioides brasiliensis, the causative agent of paracoccidioidomycosis, is known for its characteristic multiple budding, where a central mother cell can have several buds, giving it a "mariner's wheel" appearance.

Answer 65

d. Paracoccidioidomycosis Rationale: Clinical Presentation: The description of multiply budding yeast cells is characteristic of Paracoccidioides brasiliensis, the causative agent of paracoccidioidomycosis. This fungus typically presents with oral lesions that may be ulcerative, resembling the case described. Geographical Context: The patient being from Colombia is a significant clue, as paracoccidioidomycosis is endemic to parts of Central and South America, including Colombia. Morphology: Paracoccidioides brasiliensis is known for its "mariner's wheel" appearance due to multiple buds forming from a parent yeast cell, which matches the description of "multiply budding yeast cells."

Answer 66

a. Malassezia furfur Rationale: Tinea versicolor (pityriasis versicolor) is caused by Malassezia furfur, a yeast that affects the skin and alters pigment production, leading to hypopigmented or hyperpigmented areas.

Answer 67

c. Trichophyton tonsurans Rationale: Trichophyton tonsurans does not cause fluorescence of infected hairs under Wood's lamp examination. This characteristic is specific to certain species of Microsporum, which do fluoresce.

Answer 68

C. All of the choices are correct Rationale: The description of circular patches on glabrous skin with an advancing red, vesiculated border and central scaling can refer to ringworm, tinea corporis, and generally to a dermatophyte infection. These terms are often used interchangeably in clinical settings to describe cutaneous fungal infections caused by dermatophytes.

Answer 69

b. Acute infections are associated with zoophilic dermatophytes, such as Microsporum canis Rationale: Zoophilic dermatophytes, such as Microsporum canis, typically cause more inflammatory (acute) reactions due to less adaptation to the human host, compared to anthropophilic dermatophytes which tend to cause more chronic, less inflammatory infections.

Answer 70

b. In tissue, one finds large, thick-walled, single budding yeast cell with broad connections between the parent yeast and bud Rationale: This is a correct description of Blastomyces dermatitidis, the causative agent of blastomycosis, which is known for this distinctive morphological feature in tissue specimens.

Answer 71

c. Microsporum Rationale: Microsporum species produce ectothrix infection, where spores form a sheath around the outside of the hair. This is distinct from Trichophyton tonsurans, which typically produces endothrix infections with spores inside the hair shaft.

Answer 72

b. The etiologic agents in inherently resistant to amphotericin B Rationale: This statement is incorrect. Paracoccidioides brasiliensis, the etiologic agent of paracoccidioidomycosis, is not inherently resistant to amphotericin B, which can be used effectively in severe cases.

Answer 73

D. Dermatophytes Rationale: Vesicular lesions related to dermatophyte infections (e.g., due to Trichophyton species) that appear in other parts of the body are indicative of an id reaction (dermatophytid or fungus id reaction), which is an allergic reaction to the fungus. Correct answer: c. Candida albicans

Answer 74

c. Candida albicans Rationale: Candida albicans often causes vaginal infections characterized by severe itching and a thick, yellow, cheesy discharge. This is typical of candidiasis (yeast infection), distinguishing it from bacterial and other protozoal infections.

Answer 75

a. Arthroconidia **Rationale:** - **Definition of Arthroconidia**: Arthroconidia are a type of fungal spore that forms by the fragmentation of septate hyphae, where segments of the hyphae develop thick walls and separate into individual cells. These are typically dry, thick-walled, and can be quite resilient. - **Morphological Fit**: The description specifies that these conidia are thick-walled and spherical, produced from terminal or intercalary hyphal cells. Arthroconidia can indeed be spherical and are produced as segments of existing hyphae, which corresponds to being formed from terminal or intercalary cells. This type of conidia is distinguished from: - **Blastoconidia**, which typically bud off from a parent yeast cell rather than forming through segmentation of hyphae. - **Phialoconidia**, which are produced in a vase-like phialide and are typically not described as thick-walled or spherical. Thus, arthroconidia best matches the description given, aligning with their formation process and structural characteristics.

Answer 76

d. Lungs Rationale: For systemic mycoses, such as histoplasmosis, coccidioidomycosis, blastomycosis, and others, the primary portal of entry is the lungs, where the fungal spores are inhaled and initially colonize before potentially disseminating to other parts of the body.

Answer 77

b. Fungal spores are all sexually produced Rationale: Not all fungal spores are sexually produced; many fungi also produce spores asexually. Fungi are indeed eukaryotic organisms, their nuclei do have nuclear membranes, and their cytoplasmic membranes contain ergosterol, not glycerol, which is characteristic of bacterial membranes.

Answer 78

c. Both yeasts and molds have a cell wall made of peptidoglycan Rationale: The cell walls of fungi are made of chitin, not peptidoglycan, which is found in bacterial cell walls. Molds form elongated filaments (hyphae), yeasts reproduce by budding, and thermally dimorphic fungi change form based on temperature.

Answer 79

a. Molds produce hyphae that may or may not be partitioned with cross-walls or septa Rationale: This statement is correct. Molds can have hyphae that are septate (with cross-walls) or coenocytic (without septa). The other statements are incorrect: yeasts do have cell walls, not all yeasts produce pseudohyphae, and conidia are generally produced via asexual reproduction.

Answer 80

b. Microsporum nanum Rationale: Microsporum nanum is known for infecting pigs. Microsporum canis (dogs) Microsporum gallinae (fowl) Microsporum nanum (pigs) Trichophyton equinum (horses) Trichophyton verrucosum (cattle)

Answer 81

d. Trichophyton verrucosum Rationale: Trichophyton verrucosum is commonly associated with cattle, causing ringworm in these animals.

Answer 82

d. None of the above Rationale: All listed options (use of steroids, use of antibiotics, intake of glucose) are known risk factors for oral thrush caused by Candida spp., as they can disrupt normal microbial balance or affect immune function.

Answer 83

b. nystatin Rationale: Nystatin is typically used for topical or local treatment of candidiasis, particularly for oral or intestinal infections, not systemic treatment. Amphotericin B, caspofungin, and fluconazole are used for systemic treatment of candidiasis, which can involve more severe or disseminated infections.