Microbiology USMLE Step 1 High Yield Images
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Transcript of Microbiology USMLE Step 1 High Yield Images
Vanisha Patel Page 1
Microbiology Lab Final – TA Review
The Helminths I. Nematoda
a. Trichinella i. Eating uncooked meat ii. Eating wild game (polar bear) iii. Travel to Mexico + Asia iv. LAB
1. Muscle biopsy – encysts in muscle
v. TX
1. Albendazole b. Ascaris
i. Children of tropical/developing countries ii. LAB
1. Stool for eggs
iii. TX
1. Albendazole
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c. Strongyloidiasis i. LAB
1. Larvae in stool
ii. TX
1. Ivermectin d. Enterobiasis
i. Pinworm ii. LAB
1. Scotch tape test 2. NIH swab
iii. TX 1. Albendazole
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II. Cestoda a. Taenia saginata
i. Beef tapeworm
ii. TX
1. Niclosamide 2. Praziquantel
b. Taenia solium i. Pork tapeworm ii. Causes Cysticerosis – cysts in brain
iii. LAB 1. Swiss cheese appearance – Giant brain lesion
iv. TX
1. Niclosamide 2. Albendazole + Prednisolone
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c. Diphyllobothrium latum i. Fish tapeworm ii. Competes w/host for Vit B12 iii. TX
1. Praziquantel d. Echinococcus granulosus
i. Dog tapeworm ii. Contaminated w/canine feces
iii. LAB 1. Hydatid cyst in tissues
iv. TX 1. Albendazole
III. Trematoda a. Schistosomiasis
i. Blood flukes ii. Snail host
iii. LAB 1. Eggs in stool/urine
iv. TX 1. Praziquantel
IV. Entamoeba Histolytica a. Liver abscess, bloody diarrhea b. Flask shaped ulcers c. LAB
i. Bloody stool – cysts w/4 nuclei
d. TX
i. Metronidazole
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V. Giardia Lamblia a. Hiker’s diarrhea b. Bloating flatulence, foul smelling diarrhea c. LAB
i. Trophozoite/cyst
d. TX
i. Metronidazole VI. Trichomonas Vaginalis
a. Sexually transmitted flagellate b. Pear shaped, 4 anterior flagella c. Corkscrew motility d. Foul smelling greenish, yellow frothy discharge e. TX
i. Metronidazole
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Mycoses I. Superficial Mycoses
a. ONLY cosmetic problem* b. Pityriasis Versicolor
i. Caused by Malassezia Furfur ii. Dry, scaly, hyper/hypopigmented lesions on torso, arms, and abdomen
iii. LAB 1. Spaghetti + meatball appearance – KOH prep
iv. TX
1. Selenium Sulfide 2. Topical Miconazole
II. Cutaneous Mycoses a. Dermatophytosis
i. Trichophyton – hair, skin, nails
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ii. Microsporum – skin, hair
iii. Epidermophyton – skin, nails
iv. Diseases
1. Tinea capitis – caused by T. tonsurans 2. Tinea barbae – area of alopecia 3. Tinea pedis – caused by T. rubrum 4. Tinea cruris – caused by T. rubrum
v. LAB
1. Digested with KOH see septate hyphae & calcofluor white
2. Wood’s light (UV light)
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vi. TX 1. Skin – Ketaconazole, Miconazole, Clotrimazole 2. Hair – Ketoconazole shampoo 3. Nail – Oral Terbinafine/Itraconazole
III. Subcutaneous Mycoses a. Sporotrichosis
i. Rose Gardner’s Disease 1. Caused by sporothrix schenkii 2. Dimorphic
ii. LAB 1. Tissue biopsy: cigar shaped budding yeast 2. Room temperature: daisy shaped conidia
iii. TX
1. Oral potassium iodide 2. Systemic – Itraconzaole/Amphotericin B
IV. Systemic Mycoses a. Coccidiomycoses
i. Cali, Arizona, New Mexico ii. Inhalation of arthroconidia
iii. LAB 1. Tissue biopsy: spherules w/endospores 2. Room temperature: branched hyphae w/arthrospores
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iv. TX
1. Fluconazole 2. Amphotericin B 3. Itraconazole
b. Histoplasmosis i. Ohio, Mississippi ii. Bat feces, soil contaminated with bird droppings
iii. LAB
1. Giemsa/Wright stain 2. Tissue biopsy: Yeast w/in macrophage
3. Room temperature: tuberculated macronida on hyphae
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iv. TX
1. Self limiting 2. Itraconazole/Amphotericin B
c. Blastomycosis i. North, Central, Southeast USA ii. Decaying vegetation, soil contaminated w/beaver exreta
iii. LAB 1. Tissue biopsy: Broad based budding yeast in KOH
2. Room temperature: branched hyphae iv. TX
1. Itraconazole 2. Amphotericin B
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d. Paracoccidiomycosis i. Central + South America
ii. LAB 1. Pilot/captain wheel
2. Yeast w/multiple buds
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Opportunistic Mycoses I. Candidiasis
a. Caused by C. albicans b. Diseases
i. Oral thrush ii. Diaper rash iii. Vaginitis
c. LAB i. Culture: smooth, creamy, pasty colonies
ii. Gomorri silver methanamine
iii. ELISA iv. Stain: yeast like budding cells w/pseudohyphae
d. TX
i. Fluconazole ii. Itraconazole iii. Voricanazole iv. Nystatin (oral) v. Amphotericin B vi. Caspofungin
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II. Cryptococcosis a. Caused by C. neoformans
b. Capsule = halo ONLY opportunistic fungi w/capsule c. Pigeon droppings d. LAB
i. India Ink ii. Budding cells w/halo and prominent capsule
e. TX
i. Amphotericin B ii. Flucytosin iii. Oral fluconazole
III. Aspergillosis a. Diseases
i. Invasive aspergillosis ii. Farmer’s lung iii. Bronchopulmonary aspergillosis
b. LAB i. Tissue biopsy: dichotomous branching hyphae w/45° septate
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c. TX
i. Itraconazole ii. Amphotericin B iii. Caspofungin
IV. Zygomycosis a. Found in soil, strawberries, moist bread b. Diseases
i. Rhinocerebral zygomycosis c. LAB
i. KOH w/calcofluor white stain ii. Broad, ribbon like, nonseptate hyphae @ 90°
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d. TX
i. Amphotericin B V. Pneumocystis
a. Diseases i. Pneumocystis pneumonia – ground glass appearance
b. LAB i. H&E: Alveoli w/foamy honeycomb appearance
ii. Lung biopsy: cysts-dark oval bodies on silver stain iii. Toluidine blue-Ostain iv. Giemsa stain v. Calcofluor white
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c. TX i. TMP-SMX i. Pentamidine
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Virology I. DNA Viruses
a. Breakdown i. Enveloped
1. Double stranded a. Herpes b. Hepadno c. Pox*
ii. Naked 1. Double stranded
a. Papova b. Adeno
2. Single stranded* a. Parvo*
b. Herpes i. Enveloped, Icosahedral
ii. Alpha 1. HSV-1
a. Latent in DRG b. Syncitium formation c. Giant cell formation d. Cowdry bodies
2. HSV-2 a. Latent in lumbosacral region b. Diseases
i. Herpes Whitlow ii. Herpes Encephalitis iii. Herpes Genitalis iv. Neonatal Herpes
c. LAB i. Cowdry Type A inclusion bodies
ii. PCR = gold standard method d. TX
i. Acyclovir 3. VZV
a. Latent in sensory nerve ganglion b. Diseases
i. Chicken pox dew drop rose petal vesicular lesions
ii. Herpes Zoster c. LAB
i. Tzanck smear – intranuclear inclusion bodies d. TX
i. Acyclovir ii. Foscarnet
iii. Beta 1. CMV (HHV-5)
a. Latent in monocytes, macrophages, lymphocytes* b. Diseases
i. Mononucleosis like syndrome – Heterophil Ab NEGATIVE
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c. LAB i. Owl’s eye basophilic inclusion bodies
d. TX i. Gancyclovir ii. Foscarnet iii. Cidofavir
2. HHV 6 + 7 (Roseola) a. Biphasic
iv. Gamma 1. EBV
a. Latent in B cells b. Downey cells (atypical T cells) c. LAB
i. Monospot test – Heterophile Ab POSITIVE d. Diseases
i. Infectious Mononucleosis ii. Burkitt’s lymphoma iii. Hairy oral leukoplakia
2. HHV-8 a. Kaposki sarcoma b. AIDS
c. Hepadna i. Enveloped ii. Dane particle* iii. Ground glass appearance* iv. Serology
1. 3 antigens a. HbsAg – ACUTE b. HbcAg – Viral multiplication c. HbeAg – BEWARE (HIGH infectivity)
2. 4 antibodies a. Anti HBs/HbsAb – immunized b. Anti HbcAg-IgM – active infection c. Anti hbcAg-IgG – chronic/post infection d. Anti Hbe – low infectivity
d. Pox i. Replicates in cytoplasm* ii. Bullet shaped iii. Enveloped iv. Diseases
1. Smallpox – cytoplasmic inclusion bodies 2. Molluscum contagiosum – pearly freshly colored benign nodule
v. TX 1. Prednisone, Methotrexate
e. Papova i. Polyoma
1. Naked, circular 2. Latent in kidney 3. Diseases
a. BK
b. JC PML
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ii. Papilloma 1. HPV 6,11; 16,18; 1,4 2. Diseases
a. Plantar/palmar warts – HPV 1,4 b. Condyloma acuminate – HPV 6, 11 c. Cervical intraepithelial neoplasia – HPV 16, 18
i. Koilocytes in PAP smear 3. TX
a. Cidofavir f. Adeno
i. Naked ii. Spikes iii. Diseases
1. Acute febrile pharyngitis 2. Acute respiratory diseases – military 3. Pharyngocojunctival fever 4. 2nd MCC of infantile diarrhea
iv. Intranuclear inclusion bodies g. Parvo
i. ssDNA, naked ii. Smallest iii. Erythroid progenitor cell of BM = target iv. Diseases
1. Erythema infectiosum 2. Aplastic anemia 3. Hydrops fetalis
II. RNA Viruses a. Breakdown
i. Single stranded 1. (-) stranded
a. Enveloped i. Filo ii. Orthomyxo/influenza iii. Bunya iv. Rhabdo v. Arena vi. Paramyxo
2. (+) stranded a. enveloped
i. Toga ii. Flavi iii. Corona iv. Retro
b. Naked
i. Picorna ii. Calici
ii. Double stranded 1. Naked
a. Reo
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Antimicrobial Susceptibility Testing I. Disc Diffusion susceptibility test – Kirby- Bauer Test
a. Compares susceptibility of antibiotics
II. MIC – Minimum Inhibitory Concentration
a. Tells minimum concentration of drug that kills bacteria III. MBC – Minimum Bacteriocidal Concentration
a. Tells minimum concentration of drug that inhibits bacteria
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IV. E Test a. Arrow MIC
i. Where inhibition of growth starts
Serological Diagnosis
I. Immunological tests a. Agglutination b. Flocculation c. Immunofluorescense
i. Chlamydia ii. HSV iii. Legionella iv. Mycoplasma v. Toxoplasma
d. ELISA i. Antigens (direct) – HBV antigen ii. Antibodies (indirect) – HIV iii. Sensitive test, used for screening iv.
e. Complement fixation f. Western blot
i. Detection of protein ii. Confirmation of HIV infection iii. Specific test
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II. HIV diagnosis a. ELISA – used as a sensitive test b. Western blot – used to confirm dx c. PCR – viral load d. EXCEPTION IN NEW BORNS
i. p24 antigen test III. NO staining used in:
a. Rickettisa b. Chlamydia c. Mycoplasma d. Mycobacterium e. Spirochetes
Random Must Knows
I. NO Cell wall a. Mycobacterium
i. Tuberculosis 1. TX
a. Isoniazid b. Rifampin c. Ethambutol d. Pyrazindamide
ii. Leprae 1. TX
a. Dapsone b. Rifampin
b. Mycoplasma i. COLD agglutinin ii. Fried egg appearance
II. Spirochete a. Borrelia burgdorferi – Lyme disease
i. Bulls-eye rash ii. LAB
1. Wright Giema stain iii. TX
1. Doxycycline b. Treponema pallidum - Syphilis
i. LAB 1. Dark field microscopy – primary syphilis 2. VDRL, FTA tests
ii. TX 1. Penicillin G
c. Leptospira i. Question mark
III. Campylobacter a. Sea gull wing appearance b. Microaerophilic @ 42°
IV. Yersinia a. Safety pin appearance