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Mycology

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mycology

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Mycology

  1. 1. Lecture Mycology Prof. Dr. Abbas Hayat
  2. 2. • Fungi are eukaryotic organisms, do not contain chlorophyll, have cell walls, filamentous structures, and produce spores. • Grow as saprophytes and decompose dead organic matter. Between 100,000 to 200,000 species depending on how they are classified. • About 300 species are presently known to be pathogenic for man.
  3. 3. Features Fungi Bacteria Nucleus eukaryotic prokaryotic Cell membrane Sterols present absent Cytoplasm Mitochondria and ER present Absent Cell wall content Chitin Peptidoglycan Spores Sexual asexual Endospores
  4. 4. 2 types 1. Yeasts 2. Molds. 1. Yeasts grow as single cells , reproduce by budding. 2. Molds grow by filamentous hyphae, and form a mat ( mycelium). Form septate and aseptate hyphae.
  5. 5. Several medically imp. Fungi are thermally Diamorphic. i.e, different structures at different temperatures. Molds in environment at ambient temperatures and as yeasts at body temperature.
  6. 6. There are four types of Mycotic diseases: 1. Hypersensitivity - allergic reaction to molds and spores. 2. Mycotoxicoses - poisoning of man and animals by feeds and food products contaminated by fungi producing toxins from the grain substrate. 3. Mycetismus- ingestion of preformed toxin (mushroom poisoning). 4. Infections. In this lecture , we shall be concerned only with the last type.
  7. 7. • The establishment of a mycotic infection depends on size of inoculum on the resistance of the host. • Severity of infection depend mostly on immunologic status of host. • Thus, the demonstration of fungi, for example, in blood drawn from an intravenous catheter can correspond to colonization of the catheter, to transient fungemia (i.e., dissemination of fungi through the blood stream), or to a true infection.
  8. 8. • Most mycotic agents are soil saprophytes and are generally not communicable from person-to-person (occasional exceptions: Candida and some dermatophytes). • Outbreaks of disease may occur, but these are due to a common environmental exposure, not communicability.
  9. 9. . CLINICAL CLASSIFICATION OF THE MYCOSES a.Superficial mycoses b. Subcutaneous mycoses c. Systemic mycoses d. Opportunistic mycoses
  10. 10. a. Superficial mycoses (or cutaneous mycoses) are fungal diseases that are confined to the outer layers of the skin, nail, or hair, (keratinized layers) rarely invading the deeper tissue or viscera. The fungi involved are called dermatophytes
  11. 11. b. Subcutaneous mycoses are confined to the subcutaneous tissue rarely spread systemically. Form deep, ulcerated skin lesions or fungating masses, most commonly involving the lower extremities. Causative organisms are soil saprophytes which are introduced through trauma to the feet or legs.
  12. 12. c. Systemic mycoses may involve deep viscera and become widely disseminated. Each fungus type has its own predilection for various organs.
  13. 13. d. Opportunistic mycoses are infections due to fungi with low inherent virulence. The etiologic agents are organisms which are common in all environments.
  14. 14. YEASTS • Yeasts are single-celled budding organisms. • They do not produce mycelia. • Colonies visible on the plates in 24-48 hours. Their soft, moist colonies resemble bacterial cultures rather than molds. • Many species of yeasts which can be pathogenic for humans. • Two most significant species: Candida albicans and Cryptococcus neoformans
  15. 15. SUPERFICIAL MYCOSES • The superficial (cutaneous) mycoses are usually confined to the outer layers of skin, hair, and nails, and do not invade living tissues. • The fungi are called dermatophytes. • Tinea means "ringworm" or "moth-like". Dermatologists use the term to refer to a variety of lesions of the skin or scalp.
  16. 16. CLINICAL MANIFESTATIONS ETIOLOGIC AGENTS • 1. Trichophyton These infect skin, hair and nails. • 2. Microsporum may infect skin and hair, rarely nails. easily identified on the scalp because infected hairs fluoresce a bright green color when illuminated with a UV- emitting Wood's light. • 3. Epidermophyton floccosum. These infect skin and nails and rarely hair
  17. 17. Trychophyton rubrum, right and left great toe. Tinea unguium. Tinea unguium (onychomycosis) - nails. Clipped and used for culture
  18. 18. Tinea versicolor on chest. Characterized by a blotchy discoloration of skin which may itch. Caused by Malassezia furfur
  19. 19. • Tinea capitis - head. Frequently found in children. • Tinea cruris - "jock itch". Infection of the groin, perineum or perianal area. • Tinea barbae - ringworm of the bearded areas of the face and neck. • Tinea pedis - "athlete's foot". Infection of toe webs and soles of feet.
  20. 20. THE ID REACTION •Patients infected with a dermatophyte may show a lesion, on the hands, from which no fungi can be recovered . • These lesions, which often occur on the dominant hand (i.e. right-handed or left-handed), are secondary to immunological sensitization to a primary lesion. •Secondary lesions will not respond to topical treatment but will resolve if the primary infection is successfully treated.
  21. 21. Subcutaneous Mycosis 1. Sporothrix schenckii: Diamorphic , occupational disease typically itroduced in gardners by a thorn, , causes pustule and spread by lymphatics. 2. Chromomycosis: soil fungi , introduced by trauma , typically in legs or during war injuries. 3. Mycetoma: enters through wounds on hand and feet and produce abscesses with draining sinuses.
  22. 22. • END OF LECTURE ONE. Thank you
  23. 23. Systemic Mycosis •Cocciodioides immitis. •Histoplasma •Blastomyces •Paracoccidiodes
  24. 24. OPPURTUNIST FUNGI 1.Cryptococcus 2. Candidiasis 3. Aspergillosis 4. Mucormycosis
  25. 25. CRYPTOCOCCOSIS (Cryptococcus neoformans) • Meningitis or pulmonary disease. • Portal of entry is the respiratory system. • Infection subacute or chronic.. symptoms begin with vision problems and headache, then progress to delirium, nuchal rigidity leading to coma and death . • CSF is examined for chemistry (elevated protein and decreased glucose), cells (usually monocytes), and evidence of the organism. • Visual demonstration of the organism (India Ink preparation) The India Ink test, which demonstrates the capsule of this yeast
  26. 26. • Cryptococcosis of lung in patient with AIDS.
  27. 27. Black grain mycetoma: subcutaneous nodule due to Madurella Mycetomatis, magnified x 100   
  28. 28. A. CANDIDIASIS (Candida albicans) • Candidiasis. Candida albicans , endogenous organism. found in 40-80% of normal human beings. • Present in the mouth, gut, and vagina, • Commensal or a pathogenic organism. • Usually alteration in cellular immunity, normal flora or normal physiology. Although most frequently infects the skin and mucosae, Candida can cause pneumonia, septicemia or endocarditis in the immuno-compromised patient
  29. 29. Gram-stain of vaginal smear showing Candida albicans epithelial cells and many gram-negative rods. (1,000X oil)
  30. 30. Oral thrush.
  31. 31. Candida albicans showing germ tube production in serum. Gram stain.
  32. 32. Aspergillus: • Aspergillus (is a genus consisting of several hundred mold species found in various climates worldwide
  33. 33. • Aspergillus species are highly aerobic and are found in almost all oxygen-rich environments, where they commonly grow as molds on the surface of a substrate, as a result of the high oxygen tension.
  34. 34. The most common causing pathogenic species • The most common pathogenic species are • Aspergillus fumigatus : causing allergic disease • Aspergillus flavus.,produces aflatoxin which is both a toxin and a carcinogen, and which can potentially contaminate foods such as nuts. • Other species are important as agricultural pathogens. Aspergillus spp. cause disease on many grain crops, especially maize, and synthesize mycotoxins including aflatoxin.
  35. 35. • Aspergillosis • Pulmonary aspergillosis. • Aspergillosis is the group of diseases caused by Aspergillus. The most common subtype among paranasal sinus infections associated with aspergillosis is Aspergillus fumigatus. • symptoms: include fever, cough, chest pain or breathlessness, Usually, only patients with already weakened immune systems or who suffer other lung conditions are susceptible.
  36. 36. Major forms of disease • Allergic bronchopulmonary aspergillosis or ABPA, which affects patients with respiratory diseases like asthma, cystic fibrosis, and sinusitis). • Acute invasive aspergillosis, a form that grows into surrounding tissue, more common in those with weakened immune systems such as AIDS or chemotherapy patients. • Disseminated invasive aspergillosis, an infection spread widely through the body. • Aspergilloma, a "fungus ball" that can form within cavities such as the lung
  37. 37. Fungus ball of Aspergillus
  38. 38. Nasal aspergillosis
  39. 39. DIAGNOSIS 1. Skin scrapings suspected to contain dermatophytes or pus from a lesion can be mounted in KOH on a slide and examined directly under the microscope. 2. Skin testing (dermal hypersensitivity). 3. Serology may be helpful when it is applied to a specific fungal disease. 4. Direct fluorescent microscopy may be used for identification. 5. Biopsy and histopathology. 6. Culture: Sabouraud dextrose agar.
  40. 40. TREATMENT The primary antifungal agents are: 1. Amphotericin B. drug of choice for most systemic fungal infection, administered I.V. (patient usually needs to be hospitalized), often for 2-3 months. The drug is rather toxic; thrombo- phlebitis, nephrotoxicity, fever, chills and anemia frequently occur during administration 2. Azoles: ketoconazole, fluconazole, oral. 3. Griseofulvin: slow-acting drug which is used for severe skin and nail infections, oral. 4. 5-fluorocytosine:inhibits RNA synthesis, oral.
  41. 41. END OF COURSE

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