Microbiology: Fungi And Antifungal Antibiotics

Front 1

How do yeast reproduce? What is a pseudohyphae?

Back 1

Budding. Pseudohyphae: when buds do not separate they form long chains of yeast cells.

Front 2

What is mycelia?

Back 2

Mycelia is another term for mold. Fungi that live as multicellular colonies composed as branching hyphae are known as mold.

Front 3

What is unique about dimorphic fungi?

Back 3

Fungi that can grow as either a yeast or mold, depending on environmental conditions and temperatures. They usually grow as a yeast at body temperatures.

Front 4

What is a dermatophyte? Name the three common dermatophytes?

Back 4

Microsporum, trichophyton, and epidermophyton. They are fungi confined to the stratum corneum and its adnexal structures. Dermatophyte = superficial mycoses = ring worm.

Front 5

What are the two diagnostic test used to identify cutaneous fungi?

Back 5

Wood's lamp: UVA (365) light detects fluorescent metabolites. Microsporum will fluoresce a brilliant green.

KOH preparations: KOH digests keratin, dissolved skin scrappings will reveal branched hyphae.

Front 6

What is the most common cutaneous fungi found in young children (before puberty)?

Back 6

Children most often are infected by microsporum. The family normally has a cat or dog.

Front 7

What fungi infects the outer hair shaft, causes alopecia, and has a positive Wood's lamp?

Back 7

Microsporum canis.

Front 8

Which fungi infects the inner hair shaft causing tinea capitis and is negative under a Wood's lamp?

Back 8

Trichophyton tonsurans.

Front 9

What superficial fungi will cause hypopigmentation? What would a Wood's lamp show?

Back 9

Tinea versicolor is caused by Malassezia furfur which is positive under a Wood's lamp. This fungi inhibits melanosome transfer to keratinocytes.

Front 10

What fungi is this?

Back 10

Spaghetti and meatball appearance. Malassezia furfur.

Front 11

How do you treat this fungi which is infecting the hair shaft?

Back 11

White piedra: Trichosporon beigelii. Treat with topical imidazole.

Front 12

What cutaneous fungi is this?

Back 12

Trichophyte is idetified by macroconidia and microconidia.

Front 13

How do you treat this cutaneous fungi?

Back 13

Microsporum: large boat shaped macroconidia. Treat with griseofulvin or imadazole.

Front 14

What cutaneous fungi is shown?

Back 14

Epidermophyton: punching bag shape occurring in three.

Front 15

Skin scrappings from a cauliflower like skin lesion reveal this subcutaneous fungus.

Back 15

Cladosporium carrionii causes eumycotic mycetoma or chromoblastomycosis.

Front 16

Like cladosporium, this fungus causes chromoblastomycosis. Tx?

Back 16

Fonsecaea pedrosi. Tx: itraconazole or imidazole.

Front 17

Skin scrappings with KOH of a chromoblastomycosis have what characteristic?

Back 17

Copper-colored sclerotic bodies (Medlar bodies).

Front 18

How does the fungus that causes rose gardener disease spread throughout the body?

Back 18

Sporothrix schenkii infects gardeners after they are pricked by a thorn. A nodule will appear, become necrotic, and then ulcerate. New nodules will appears along lymphatics.

Front 19

How do you treat sporothrix schnekii?

Back 19

Oral potassium iodide or itraconazole.

Front 20

Cigar shaped yeast.

Back 20

Sporothrix schenckii (in vivo form).

Front 21

Patient presents with sores on his mouth and physical weakness. X-rays show calcification in his lungs and spleen. History reveals that the patient was cave exploring in Ohio. What histological finding would help you diagnose this fungal infection?

Back 21

Biopsy of a lesion will show Histoplasma capsulatum yeast within macrophages.

Front 22

What fungus is this?

Back 22

Histoplasma capsulatum. Note the yeast within macrophages.

Front 23

Name this dimorphic systemic fungus.

Back 23

Blastomyces dermatitidis. Note the broad-based bud.

Front 24

Spherules with endospores are characteristic of _________.

Back 24

Coccidioides immitis.

Front 25

A man presents with lesions on his mouth, erythema nodosum, and has flu-like symptoms. He says that he recently visited San Joaquin Valley. What does this man have?

Back 25

San Joaquin Valley fever caused by Coccidioides immitis.

Front 26

Name the fungi that cause systemic disease.

Back 26

Coccidioides immitis, Histoplasma capsulatum, Blastomyces dermatitidis. Also Paracoccidioides brasiliensis which causes South American blastomycosis.

Front 27

Patient from Michigan presents with weakness, night sweats, lung involvement. What fungus?

Back 27

Blastomycosis dermatitidis.

Front 28

What fungus causes oral thrush? How do you treat this?

Back 28

Candida albicans. Patches of white exudate with a reddish base cover mucous membranes of the mouth. Difficult to scrape off. Swish and spit with nystatin or sucking on imidazole candies.

Front 29

How is candida diagnosed?

Back 29

KOH prep. Blood test for beta-D-glucan. Germ tube test.

Front 30

What does candida albicans cause in normal hosts and in immunocompromised patients?

Back 30

Normal: oral thrush, vaginitis, diaper rash.
Immunocompromised: esophagitis and systemic infection.

Front 31

Patient on chemotherapy for leukemia develops hemoptysis. Biopsy of pulmonary tissue reveals branched hyphae. Diagnosis?

Back 31

Aspergillus fumigatus.

Front 32

This fungus dines on dead/decaying vegetations.

Back 32

Septate hyphae branching at 45 degree angle. Aspergillus fumigatus.

Front 33

What three major types of diseases does aspergillus fumigatus cause?

Back 33

Fungus ball (aspergilloma): develops in preexisting cavity in the lung. Causes hemoptysis.
Allergic bronchopulmonary aspergillosis: type I and III hypersensitivity.
Invasive aspergillosis: hemorrhagic infarctions and a necrotizing bronchopenumonia.

Front 34

What fungus secretes a certain toxin on peanuts and rice and may be associated with liver carcinomas?

Back 34

Aspergillus flavus secretes aflatoxin.

Front 35

AIDS patient with a silver stain of a lung biospy.

Back 35

Pneumocystis carinii pneumonia stains black on a silver stain.

Front 36

Name the saprophytic molds that have broad (90 degrees), non-septated, branching hyphae.

Back 36

Rhizopus, mucor.

Front 37

Diabetic patient presents with a frontal lobe mass. What fungus caused this?

Back 37

Mucor species that causes rhinocerebral mucormycosis in patients with diabetic ketoacidosis.

Front 38

India Ink stain. What does this fungus cause?

Back 38

Cryptococcus neoformans, contracted via pigeon droppings, causes meningitis and pneumonia.

Front 39

What organisms are urease positive?

Back 39

Pink color forms on urea agar.
Bacteria: Helicobacter and Proteus. Fungi: Cryptococcus neoformans.

Front 40

How does amphotericin B work?

Back 40

Amphotericin B complexes with ergosterol disrupting fungal plasma membrane leading to cell death. It is used for serious systemic fungal infections.

Front 41

What are some side effects of amphotericin B?

Back 41

Renal toxicity: dose-dependent azotemia (reversible).
Acute febrile reaction with rigors.
Anemia.
Phlebitis at IV site.

Front 42

How does flucytosine work? What are its drawbacks?

Back 42

Flucytosine is an anti-metabolite which inhibits DNA/RNA synthesis. Most fungi are resistant.

Front 43

Name the imidazoles. How do they work? Which two are used for topical fungal infections.

Back 43

Imidazoles are broad spectrum antifungals which inhibit cytochrome p-450 which is involved in ergosterol synthesis.
Ketoconazole, miconazole (topical), clotrimazole (topical).

Front 44

What are side effects of ketoconazole?

Back 44

Hepatotoxicity, GI distrubances, and symptoms due to a decrease in testosterone: gynecomastia, impotence, decreased libido, and decreased sperm production.

Front 45

What is Fluconazole used to treat?

Back 45

Candida albicans and cryptococcal meningitis (adjunct to IV amphotericin).

Front 46

Voriconazole is a broad spectrum antifungal. -azoles inhibit CYP450, which inhibits ergosterol production. What are the toxic effects of voriconazole?

Back 46

Voriconazole is a triazole (as a pose to a imidazole) and toxics effects inclue visual changes, hepatotoxicity and rash.

Front 47

Ravuconazole is used to treat ______.

Back 47

Ravuconazole (a triazole) is used to treat Rhizopus species.

Front 48

If amphotericin B is not useful in treating aspergillosis what drug is used?

Back 48

Caspofungin which inhibits fungal cell wall by inhibiting glucan synthesis.

Front 49

What antifungal is used for esophageal fungal infections?

Back 49

Nystatin.

Front 50

What is the mode of action of griseofulvin?

Back 50

Prevent mitosis by inhibiting spindle formation in fungi.

Front 51

Itraconazole inhibits cytochrome p450 which converts _____ to _____. Is this a fungicidal or fungistatic mechanism?

Back 51

Lanosterol to ergosterol. Fungistatic.

Front 52

What is the key component of fungal spores, which provides the fungus with resistance to dehydration, heat, and chemicals?

Back 52

Dipicolinic acid.

Front 53

Actinomyces and Nocardia are both gram _____. How does ones differentiate the two in the laboratory?

Back 53

Actinomyces forms sulfur granules. Nocardia is acid-fast.

Front 54

A women presents with an abscess in her mouth which is draining pus and yellowish granules. The doc says the bug is part of her normal flora, and the abscess could have formed during her recent dental surgery. What gram positive rod is this?

Back 54

Actinomyces israeli.

Front 55

Amphotercin B can cause what electrolyte imbalances?

Back 55

Hypokalemia, hypomagnesium. It also causes neuphrotoxicity, acute febrile reaction, anemia, phlebitis.