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Microbiology Part 2

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  1. Microbiology Part 2

  2. Mycology – Systemic Mycoses • Histoplasmosis • Blastomycosis • Coccidioidomycosis • Paracoccidioidomycosis

  3. These are all dimorphic fungi • Mold in the soil, yeast in tissues • Cold = mold, Heat = Yeast • All cause pneumonia, can disseminate • Tx: ketoconazole or fluconazole for local infection; Ampho B for systemic

  4. Mycology – Systemic mycoses • Histoplasmosis • Blastomycosis • Coccidioidomycosis • Paracoccidioidomycosis

  5. Histoplasmosis • Transmitted by inhalation of asexual spores • Mississippi and Ohio River Valley • Causes pneumonia • In bird or bat droppings • “HistoHides” (in macrophages)

  6. 3-5 um

  7. Mycology – Systemic Mycoses • Histoplasmosis • Blastomycosis • Coccidioidomycosis • Paracoccidioidomycosis

  8. Blastomycosis • East of Mississippi River and Central America • Cases Inflammatory lung disease, which can disseminate to skin and bone • Granulomatous nodules • “BlastoBuds Broadly” (broad-base budding yeast)

  9. 5-15um

  10. Mycology – Systemic Mycoses • Histoplasmosis • Blastomycosis • Coccidioidomycosis • Paracoccidioidomycosis

  11. Coccidioidomycosis • Transmitted by inhalation of asexual spores • Southwestern United States, California • San Joaquin Valley • Causes pneumonia and meningitis; can disseminate to bone and skin • Cases increase after earthquake • “CoccidioCrowds” – spherule filled with endospores

  12. 20-60 um

  13. Mycology – Systemic Mycoses • Histoplasmosis • Blastomycosis • Coccidioidomycosis • Paracoccidioidomycosis

  14. Paracoccidioidomycosis • Latin America • Budding yeast with “captain’s wheel” appearance • Larger than RBC

  15. 40-50 um

  16. Cutaneous mycoses - Dermatophytes • Tineaversicolor • Caused by Malasseziafurfur • Causes hypopigmented patches by degradation of lipids producing acids which damage melanocytes • Occurs in hot, humid weather • Tx: topical miconazole, selenium sulfide (Selsun) • KOH prep show “spaghetti and meatballs”

  17. Cutaneous mycoses - Dermatophytes • Tineapedis, cruris, corporis, capitis • Caused by Microporum, Trichophyton, and Epidermophyton • Pruritic lesions with central clearing resembling a ring • See mold hyphae on KOH prep • Pets are reservoir • Tx: topical azoles

  18. Opportunistic Fungal Infections • Candida albicans • Systemic or superficial • Yeast with pseudohyphae at 20°, and germ tubes at 37° • Oral and esophageal thrush in immune compromised • Vulvovaginitis • Diaper rash • Endocarditis (in IVDA) • Disseminated candidiasis • Chronic mucocutaneouscandidiasis • Tx: Nystatin for superficial infection, Ampho B for serious systemic infections

  19. Psuedohyphae and budding yeast at 20° Germ tubes at 37° Jagged edges with satellite lesions

  20. Opportunistic Fungal Infections • Aspergillusfumigatus • Mold with septatehyphae that branch at 45° • Allergic bronchopulmonaryaspergillosis • Lung cavity aspergilloma (“fungus ball”) • Invasive aspergillosis in immune compromised and pts with CGD

  21. Opportunistic Fungal Infections • Cryptococcus neoformans • Heavily encapsulated yeast • In soil, pigeon droppings • Culture on Sabouraud’s agar; stain with India Ink • Latex agglutination test to detect polysaccharide Ag • Cryptococcal meningitis; “soap bubble” lesion in brain

  22. Opportunistic Fungal Infections • Mucor and Rhizopus sp. • Mold with irregular nonseptatehyphae branching at wide angles • Mostly in ketoacidotic diabetic and leukemic patients • Proliferate in walls of blood vessels and cause infarction • Rhinocerebral, frontal lobe abscess – rapid spreading

  23. Opportunistic Fungal Infections • Pneumocystisjiroveci • Yeast; inhaled • Pneumonia in immune suppressed • Diffuse and bilateral CXR appearance • Dx: lung biopsy or lavage; silver stain • Tx: TMP-SMX, pentamidine, dapsone • Prophylaxis CD4 <200 • Sporothrixschenckii • Dimorphic fungus – cigar shaped budding yeast; lives on vegetation • Sporotricosis – “Rose gardener’s disease” • Local pustule or ulcer; follows lymphatic drainage • Tx: itraconazole, or potassium iodide

  24. Antifungals

  25. Ampho B • MOA: Binds ergosterol, forms membrane pores allowing leakage of electrolytes • Use: Systemic mycoses; intrathecally for fungal meningitis (does not cross BBB) • Toxicity: Fever/chills, nephrotoxicity, arrhythmia • Nystatin • MOA: Binds ergosterol disrupting membrane, too toxic for systemic use • Use: “Swish and swallow” for oral thrush, topical for diaper rash and vulvovaginitis • Azoles • MOA: inhibits fungal sterol synthesis • Use: systemic mycoses • Toxicity: gynecomastia, inhibits P450

  26. Flucytosine • MOA: inhibits DNA synthesis • Use: systemic mycoses with Ampho B • Toxicity: Bone marrow suppression • Caspofungin • MOA: Inhibits cell wall synthesis (inhibits synth of β-glucan) • Use: Invasive aspergillosis • Terbinafine • MOA: Inhibits fungal enzyme squaleneepoxidase • Use: dermatophytoses • Griseofulvin • MOA: interferes with microtubule function, disrupts mitosis; deposits in keratin containing tissue • Use: Oral for superficial infections; inhibits growth of dermatophytes • Toxicity: Teratogen, carcinogenic, increases P450 activity

  27. Parasites

  28. Single celled organisms • Giardialamblia • Dz: bloating, flatulence, foul-smelling fatty diarrhea, seen in campers • Transmission: cysts in water • Dx: Trophozoites or cysts in stool • Tx: Metronidazole • Entamoebahistolytica • Dz: Amebiasis – bloody diarrhea, liver abscess, RUQ pain • Transmission: cysts in water • Dx: Serology, trophozoites or cysts in stool • Tx: Metronidazole and iodoquinol

  29. Cryptosporidium • Disease: severe diarrhea in AIDS pts, mild disease in non-immunocompromised • Transmission: cysts in water • Dx: Cysts on acid-fast stain • Prevention by filtering city water • Toxoplasmagondii • Disease: brain abscess (ring-enhancing lesions); congenital toxochorioretinints, hydrocephalus, intracranial calcifications • Transmission: cysts in meat or cat feces; crosses placenta • Dx: Serology, biopsy • Tx: Sulfadiazine + pyrimethamine

  30. Naegleriafowleri • Disease: rapidly fatal meningoencepalitis • Transmission: swimming in fresh water lakes, enter via cribriform plate • Dx: Amoebas in spinal fluid • Tx: none • Trypanosoma • T. gambiense, T. rhodesiense • Disease: African sleeping sickness = enlarged LN, recurring fever, somnolence, coma • Transmission: Tsetse fly • Dx: Blood smear • Tx: Suramin for blood borne disease; melarsoprol for CNS penetration

  31. Trypanosomacruzi • Disease: Chagas disease = dilated cardiomyopathy, megacolon, megaesophagus; South America • Transmission: Reduviid bug • Dx: Blood smear • Tx: Nifurtimox • Leishmaniadonovani • Disease: Visceral leishmaniasis (kalaazar) = spiking fevers, hepatosplenomegaly, pancytopenia • Transmission: sandfly • Dx: macrophages with amastigotes • Tx: Sodium stibogluconate

  32. Plasmodium – malaria, cycle fever, HA, anemia, splenomegaly • P. vivax/ovale • Cycles QOD, dormant form in liver treated with primaquine • P. falciparum • Severe, cycles QD, RBCs with parasite occlude capillaries in brain, kidneys, lungs • P. malariae • Transmission: Anopheles mosquito • Dx: Blood smear • Tx: chloroquine, if resistance use mefloquine;primaquine for dormant form in P. vivax/ovale

  33. Babesia • Disease: Babesiosis = fever and hemolytic anemia; in NE USA • Transmission: Ixodes tick (same as Borrelia of Lyme Dz; may coinfect) • Dx: Blood smear; RBC with “Maltese Cross” • Tx: Quinine, clindamycin • Trichomonasvaginalis • Disease: vaginitis = foul-smelling greenish discharge, itching and burning • Transmission: sexual • Dx: Trophozoites on wet mount • Tx: Metronidazole

  34. Helminths - Nematodes • Enterobiusvermicularis (pinworm) • Food contaminated with eggs; intestinal infection; anal pruritis; scotch tape method • Ascarislumbricoides • Eggs visible in feces; intestinal infection; Loffler’s eosinophilicpneumonitis • Trichinellaspiralis • Undercooked meat, usually pork; inflammation of muscle, periorbital edema • Strongyloidesstercoralis • Larvae in soil penetrate skin; intestinal infection; causes vomiting, diarrhea and anemia