DIT review - Micro 9 Flashcards
1
Q
What agar is used to culture fungi?
A
Sabouraud
2
Q
What are the 4 systemic mycoses
A
Histoplasmosis
Blastomycosis
Coccidioidomycosis
Paracoccidiodomycosis
3
Q
Describe histology of Histoplasmosis including size compared to RBC
A
- Intracellular oval bodies within macrophages
- Smaller than RBC
4
Q
HIstology of blastomycosis including size compared to RBC
A
- Broad based budding
- Same size as RBC
5
Q
Histology of Coccidiodomycosis including size compared to RBC
A
- Spherules (filled with endospores)
- Larger than RBC - tubleweed bigger than sombrero
6
Q
HIstology of paracoccidiodomycosis including size compared to RBC
A
- Captains wheel
- Larger than RBC - wheel larger than red spot in center of wheel
7
Q
Describe the location of each of the systemic mycoses
A
Histo - Mississippi and Ohio river valley (midwest/central US)
Blasto - Eastern US
Coccidio - Southwest US, California
Paracoccidio - Latin america
8
Q
What is the cuase of Pityriasis versicolor
A
Malessezia furfur
9
Q
PResentation of Pityriasis versicolor
A
- More common in summer (fungus survives in hot/humid conditions)
- Hypopigmented patches
- Due to degradation of lipids that produces acids that damage melanocytes
- Confined to the stratum corneum (superficial layer)
10
Q
Histology of Malessezia
A
- Spaghetti and meatball appearance
11
Q
Treatment of Pityriasis versicolor
A
- Selenium Sulfide aka Selsun blue
12
Q
Treatmtne of tinea (dermatophyte) aka ring worm
A
- Topical azoles
- Griseofulvin for more severe infections
- Onychomycosis – oral Terinafine
13
Q
Presentation and treatment of Sporothrix Schenckii
A
- “Rose gardener’s disease”
- Dimorphic
- Cigar-shaped yeast
- Presentation:
- Local pustule or ulcer at site of trauma
- Ascending lymphangitis (nodules along draining lymph nodes)
- Treatment:
- Itraconazole
- Potassium iodide (THINK: plant a rose in the pot”)
14
Q
What are the only catalase positive fungi
A
Candida, Aspergillus
15
Q
Histology of Candida at 20 C
A
- 20C – yeast: pseudohyphae and budding yeasts
16
Q
Histology of candida at 37 C
A
- 37C – mold: germ tubes
17
Q
Describe risk factors and pH of candida vulvovaginosis
A
- Vulvovaginitis
- Associated with diabetes and antibiotic use
- Normal vaginal pH (vs. Gardnerella and Trichomonas which have pH > 4.5)
18
Q
Describe histology of Aspergillus
A
- Septate hyphae branching at 45 acute angle
- Produces conidia in radiating chains at end of conidiophore
19
Q
Presentation of Aspergillus
A
- Allergic bronchopulmonary aspergillus (wheezing, fever, pulmonary infiltrate) – HSR Type I
- Associated with asthma and cystic fibrosis
- Aspergillomas (solid balls of fungi) in pre-existing cavities
- Angioinvasive aspergillosis (fever, cough, hemoptysis)
- Kidney failure, ring enhancing brain lesions, paranasal necrosis
- Aflatoxin can cause hepatocellular carcinoma
20
Q
Characteristics of Cyptococcus neoformans
A
- Heavily encapsulated
- Urease positive
- Found in soil and pigeon droppings
21
Q
Presentaton of crytococcus
A
- Pneumonia, meningitis, encephalitis (“soap bubble” lesions in brain)
22
Q
Name 3 different ways to diagnose Cryptococcus
A
- Bronchopulmonary washing of lung tissue
- Stain sample with mucicarmine red methanamine silver stain
- Lumbar puncture
- Stain with India ink – will show clear halo
- Latex agglutination
- Detects polysaccharide capsular antigen
23
Q
Treatment of cryptococcus
A
- Amphotericin B + Flucytosine, followed by maintenance with Fluconazole
24
Q
MOA and uses of Amphotericin B
A
- MOA:
- Binds Ergosterol in cell membrane and forms pores leading to fungal cell death
- Usually given IV
- Can also be given intrathecally (into spinal theca) for CNS infections
- Uses:
- Serious, systemic mycoses
- Cryptococcus, blastomycosis, coccidiodomycosis, aspergillosis, histoplasmosis, mucormycosis
*
25
Adverse effects of Amphotericin B
* Fever/chills, hypotension. IV phlebitis, _Nephrotoxicity_, Hypokalemia, hypomagnesemia, Arrhythmias, anemia
26
MOA and uses of Nystatin
* MOA:
* Binds Ergosterol in cell membrane and forms pores leading to fungal cell death
* Usually given topically (too toxic for IV use)
* Uses:
* Cutaneous candidiasis – diaper rash, vulvovaginitis
* Oropharyngeal candidiasis – “swish and swallow”
27
MOA, uses, and adverse effects of Flucytosine
* MOA:
* Inhibits DNA and RNA biosynthesis by being converted to 5-fluorouracil by cytosine deaminase
* Uses:
* Used in combo with Amphotericin B to treat Cryptococcus and systemic candida
* Adverse effects:
* Bone marrow suppression
28
MOA of Azoles
* Inhibits synthesis of Ergosterol in cell wall
* Inhibits P450 enzyme that converts Lanosterol to Ergosterol
29
Specific uses of each to the following azoles:
* Fluconazole
* Itraconazole
* Voriconazole
* Clotrimazole
* Miconazole
* ses:
* Fluconazole – cryptococcal meningitis
* Itraconazole – dimorphic fungi: blastomycosis, Histoplasma, coccidiodes
* Voriconazole – asperigillus
* Clotrimazole – tinea
* Miconazole – tinea
30
Adverse effects of azole
* Liver dysfunction – CYP-450 inhibitor
* Testosterone synthesis inhibition (gynecomastia) – especially with ketoconazole
* Blurry vision, changes in vision color, flashes of light (Voriconazole)
31
MOA of Echinocandins
* Drugs:
* Caspofungin
* MOA:
* Inhibits cell _wall_ synthesis by inhibit synthesis of beta-glucan
* Vs. other drugs which affect cell membrane
32
Uses and adverse effects of Echinocandin
* Uses:
* Invasive aspergillosis, candida infection
* THINK: cASPogungin = ASPergillus
* Adverse effects:
* GI upset
* Flushing (due to histamine)
33
MOA, uses, and adverse effects of Terbinafine
* MOA:
* Inhibits fungal enzyme squalene epoxidase, leading to decreased Ergosterol synthesis (cell membrane)
* Squalene epoxidase catalyzes squalene to lanosterol (lanosterol is then converted to Ergosterol)
* Uses:
* Dermatophytes
* Topical = tinea pedis and corporis
* Oral = onychomycosis and tinea capitis
* Adverse effects:
* GI upset
* Hepatotoxicity
34
MOA, uses, and adverse effects of Griseofulvin
* MOA:
* Targets microtubule function, inhibiting mitosis
* Deposits in keratin-containing tissue (e.g. skin, hair, nails)
* Uses:
* Dermatophytes
* Adverse effects:
* Teratogen
* Confusion, HA
* Carcinogenic
* CYP-450 inducer
35
Transmission of giardia
* Cysts in water (fecal-oral)
36
Diagnosis of giardia
* Multinucleated trophozoites in stool
* Cysts in stools (image)
37
Transmission and presentation of entamoeba histolytica
* Transmission:
* Cysts in water
* Presentation:
* Causes amebiasis
* Bloody diarrhea
* Liver abscess – RUQ pain with “anchovy paste” exudate
* Flask-shaped ulcers in colon on histology
38
Describe trophozoites of entamoeba
* Trophozoite with engulfed RBCs in stool
39
Describe cysts of entamoeba
* Cysts with up to 4 nuclei in stool
40
Treatment of entamoeba
* Metronidazole – kills trophozoites
* Paramycin – luminal agent to kill cysts
* Iodoquinol – luminal agent to kill cysts
41
Transmission and presentation of cryptosporidium
* Transmission:
* Oocysts in water
* Presentation:
* Severe diarrhea in HIV patients
* Mild watery diarrhea in immunocompetent
42
Diagnosis of cryptosporidium
* Oocyts in acid-fast stain
43
Treatment of cryptosporidium
* Prevention via water filtering
* Nitazoxanide in immunocompetent hosts
* Spiramycin (macrolide)
44
3 modes of transmission of Toxoplasma gondii
* Cysts in raw/undercooked meat
* Oocyst in cat feces
* Crosses the placenta
45
Presentation of congenital toxo?
* Triad: chorioretinitis, hydrocephalus, intracranial calcifications
* Also deafness
46
Presentation of toxo in AIDs patients
HIV – brain abscess with ring-enhancing lesions
Brain biopsy to differentiate from CNS lymphoma (other cause of ring-enhancing lesion
47
Treatment of Toxo
* Sulfadiazine + pyrimethamine
* TMP-SMX prophylaxis CD4 \< 100 + IgG positive for Toxo
48
Transmission and presentation of Trypanosoma bruceii
* Transmission:
* Tsetse fly (painful bite)
* Presentation:
* African sleeping sickness
* Enlarged lymph nodes, recurring fever, somnolence, coma
* Recurring fevers due to antigenic variation, preventing host from forming immune response
49
Diagnosis and treatment of trypanosoma bruceii
* Diagnosis:
* Trypomastigote on blood smear
* Have a single flagella
* Treatment:
* Suramin = blood borne disease
* Melarsoprol = CNS penetration
