Medical Mycology PDF

# MEDICAL MYCOLOGY Dr.Mohamed alhassan Taha Faculty of Medicine, University of Gezira ## MYCOLOGY - Definition: - Mykes (Greek word) =Mushroom - Ology =Study of. - **Mycology:** is the branch of biology concerned with the study of fungi and fungal infections. ## Medical Mycology: is the...

# MEDICAL MYCOLOGY Dr.Mohamed alhassan Taha Faculty of Medicine, University of Gezira ## MYCOLOGY - Definition: - Mykes (Greek word) =Mushroom - Ology =Study of. - **Mycology:** is the branch of biology concerned with the study of fungi and fungal infections. ## Medical Mycology: is the study of fungi that cause diseases in human. ## Fungi - There are thousands (200.000) species of fungi. - Most of them are saprophytes in the soil, on vegetation in water, air... - Some fungi affect human life in positive manner. - Few species are pathogenic (opportunistic). ## Food - The image shows a cluster of brown mushrooms next to some white mushrooms in a dish. ## Drugs - The image shows a vial labeled "Procaine Penicile for injection" next to a microscopic image of *Penicillium notatum*. ## Bread; cheese; yoghurt... - The image shows a box of instant yeast and a spoon with a small amount of yeast scooped out of it. ## HISTORY - Raymond Jacques Sabouraud (1846 – 1938) - Father of Medical Mycology ## Fungi-Structure - **Are eukaryotic organisms;** having true nuceli and nuclear membrane. - Have a rigid cell wall consists of chitin;, mannan and glucan thus fungi are insensitive to antibiotics. - Their cell membrane contains **ergosterol**. ## Fungal Structure - An image shows a diagram of the cell of a fungus: - **Cell wall** - **Mitochondrion** - **Plasma membrane** - **Nucleus** - An image of a fungal cell wall shows it's made up of: - **Chitin** - **Cytoplasmic membrane** - **Fibrillar proteins** - **Mannoprotein** - **Glucan** ## Nutrition: - Their natural habitat is soil; or water contain decaying organic matter - They obtain nutrients as saprophytes or as parasites. - Fungi are aerobes & facultative anaerobes. ## Morphology - Depending on cell morphology, fungi are: - (A) Yeast; - (B) Molds; and - (C) Dimorphic ## 1. Yeasts - Are unicellular. - Can be oval, round cells. - Reproduce by a sexual budding to form blastospores - Example: *Cryptococcus neoformans*. ## Yeast-like fungi: - Are yeasts with pseudohyphae form a tube. - Some times form mycelia - e.g. *Candida albicans*. ## 2.Molds/ Moulds - Are also known as filamentous fungi. - They are branching filaments (hyphae) which contain cytoplasm and nuclei. - Hyphae may be septate or non-septate. - They grow by apical extension to form a intertwined mass known as mycelium. - Filamentous fungi are multicellular. - Example: *Dermatophytes*. - An image shows a microscopic image of hyphae next to a diagram of mycelium made of hyphae labeled "Mycelium" and "Hypha." ## 3.Dimorphic fungi - Fungi existing in two different forms at two different environmental conditions (temperature) - at room temperature: moulds - at body temperature: yeast - Example: - *Histoplasma capsulatum*. ## Fugal Reproduction - Fungi can reproduce sexually or a sexually. - Based on sexual spore formation. - Four types - 1. *Zygomycetes* - 2. *Ascomycetes* - 3. *Basidiomycetyes* - 4. *Deuteromycetes* ## EPIDEMIOLOGY - Infection is acquired by inhalation, ingestion or traumatic implantation. - Some yeasts are human commensals and cause endogenous infections when there is some imbalance in the host. - Only dermatophyte infections are truly contagious. - Many fungal diseases have a worldwide distribution, but some are endemic to specific geographical regions. - Intact skin is an effective host defense against certain fungi (e.g., *Candida*, dermatophytes), but if the skin is damaged, organisms can become established. - Fatty acids in the skin inhibit dermatophyte growth, and hormone-associated skin changes at puberty limit ringworm of the scalp. - The normal flora of the skin and mucous membranes suppress fungi. When the normal flora is inhibited, e.g., by antibiotics, overgrowth of fungi such as *C. albicans* can occur. ## Virulence mechanism - Ability to adhere to host cells by way of cell wall glycoproteins - Ability to damage host by secreting enzymes such as keratinase, elastase, collagenase - Ability to secrete mycotoxins ## Clinical Classification - Of some 200,000 fungal species, only about 100 have pathogenic potential for humans. Of these, only a few species account for most clinically important fungal infections (mycoses). - Fungal infections are classified into: - Superficial; - Cutaneous; - Subcutaneous; - Systemic; and - Opportunistic. ## Clinical Classification | Category | Mycosis | |---|---| | Superficial | Pityriasis versicolor| |Superficial | Tinea nigra| |Superficial | White piedra| |Superficial| Black piedra| | Cutaneous | Dermatophytosis| |Cutaneous| Candidiasis of skin, mucosa, or nails| | Subcutaneous | Sporotrichosis| |Subcutaneous| Chromoblastomycosis| |Subcutaneous| Mycetoma| |Subcutaneous| Phaeohyphomycosis| | Endemic (primary, systemic) | Coccidioidomycosis| |Endemic (primary, systemic)| Histoplasmosis| |Endemic (primary, systemic)| Blastomycosis | |Endemic (primary, systemic) | Paracoccidioidomycosis| | Opportunistic | Systemic candidiasis| |Opportunistic| Cryptococcosis| |Opportunistic| Aspergillosis | |Opportunistic| Hyalohyphomycosis | |Opportunistic| Phaeohyphomycosis| |Opportunistic| Mucormycosis (zygomycosis)| |Opportunistic| Pneumocystis pneumonia| |Opportunistic| Penicilliosis| ## Superficial mycoses - The image shows a man's bare chest with multiple round red spots. ## Cutaneous Mycoses - Fungal infections that involve keratinized tissues as skin, hair and nails. - They are among the most prevalent infections in the world. - The most important of these are *dermatophytes*. ## Subcutaneous mycoses - The image shows three different zoomed-in images of skin lesions. ## Systemic mycoses - Also called endemic mycoses. - Begin as primary pulmonary lesions that may disseminate to any organ where the fungi can invade and destroy the tissue. - Caused by dimorphic fungi. ## Opportunistic mycoses - Fungal infections that affect immunocompromised patients. - Examples: - Candidiasis - Cryptococcosis - Pneumocystis jiroveci pneumonia - Aspergillosis - Mucormycosis ## Laboratory Diagnosis - Diagnosis of fungal infections is based on combination of clinical observation and laboratory investigation. - There are four approaches to the laboratory diagnosis of fungal diseases: - (1) Direct microscopic examination, - (2) Culture of the organism, - (3) Serological tests, and - (4) DNA probe tests. ## Specimens: - Depends on site affected: - Superficial or cutaneous mycosis, we collect skin scraping, scalp scraping, nail clipping - Swabs should be collected from suspected *candida*. - Subcutaneous= pus containing grains/ biopsy. - Deep mycosis= sputum or pleural aspiration is collected. - Disseminated infections: blood and CSF - The image shows a close-up of someone collecting a nail sample. - Another image shoes a close-up of someone using an instrument to collect a skin sample. ## Direct microscopy: - Potassium Hydroxide (KOH) Preparation: - The specimen placed in a drop of 10%-20% KOH on a slide covered with a coverslip can be observed under a microscope. - KOH digests cells and tissue materials enabling to see fungal cells. ## Stains: - Gram's stain: for yeast and yeast like fungi - Violet colored oval / spherical cells - India Ink: for negative staining of capsulated yeast - Calcofluor white (CFW) - Geimsa staining - Fluorescent staining - Two images show microscopic details on a slide. One is of a yeast colony and the other of a fungal colony. ## 2.Culture - Sabouraud dextrose agar and 4% malt extract agar are most commonly used. - The image shows a petri dish with circular colonies growing on a medium. - The image shows a petri dish with 16 circular colonies growing on a medium. ## 3.Serology - Tests for the presence of antibodies in the patient's serum or spinal fluid are useful in diagnosing systemic mycoses but less so in diagnosing other fungal infections. - The most common tests for fungal antibodies are: - Immunodiffision - Countercurrent immuno-electrophoresis (CIE) - Whole cell agglutination - For antigen detection the followings are used: - Latex particle agglutination - ELISA ## latex agglutination test - The image shows a close-up of someone performing a latex agglutination test. ## ELISA - The image shows a microplate with a yellow liquid in each well of the plate. ## 4. PCR - Detection of fungal DNA in clinical material, principally blood, serum, Broncho-alveolar lavage fluid and sputum, is increasingly used for diagnosis. ## TREATMENT - By using antifungal agents: - In the form of creams; shampoo; tablets or injections. - The most commonly used drugs are: - Amphotericin B; - Mycostatin - Azole drugs: - Fluconazole; ketoconazole; itraconazole