Mycology Intro .pptx

INTRODUCTION TO MYCOLOGY Did you know… Bread would be flat without fungus Fungus is also crucial in making many wines and cheeses! Many antibiotics wouldn’t exist without fungus? Mushrooms that we enjoy on pizza are fungi! MYCOLOGY FUNGI: - Large group of organisms with varied forms and habits - Som...

INTRODUCTION TO MYCOLOGY Did you know… Bread would be flat without fungus Fungus is also crucial in making many wines and cheeses! Many antibiotics wouldn’t exist without fungus? Mushrooms that we enjoy on pizza are fungi! MYCOLOGY FUNGI: - Large group of organisms with varied forms and habits - Some are pathogenic for man, animals and plants  others are saprophytic and inhabit the soil breaking down dead organic matter.  Some saprophytic species are used in the production of substances of commercial importance e.g. antibiotics.  may be unicellular or multi-cellular. Classification of Fungi Based on morphology: Yeast Mold Dimorphic fungi - two distinct morphological forms. A mold phase at 25-300C and yeast phase when cultured at 35-370C (Candida is not truly dimorphic). Morphology of Fungi Hypha - long, branching, filamentous structure of a fungus that are the main mode of vegetative growth, and are collectively called a mycelium. True hyphae Pseudo hyphae Colour of hyphae Hyaline fungi: - Clear, transparent, colourless hyphae eg. Aspergillus, Fusarium, Penicillium, Paecilomyces Dematiaceous fungi/dark molds: - Having structures that are brown to black (due to melanotic pigment in the cell wall) – proper name is phaeohyphomycoses- prefix phaeo means dark pigment eg. Exophiala, Phialophora, Cladosporium Curvularia, Alternaria Morphology of Fungi Aerial hyphae: hyphae above the agar surface Vegetative hyphae: hyphae below the surface of the agar or substrate Morphology of Fungi Budding: A process of asexual reproduction in which the new cell develops as a similar outgrowth from the older parent cell (yeast or yeast-like fungi) Reproduction and sporulation Spore - propagule that develops by sexual reproduction (meiosis) or by asexual means (mitosis). Germinate to produce new colonies. Conidium/conidia - an asexual propagule that forms on the side or the end of the hypha or conidiophore Asexual vegetative spores Blastoconidia/ Blastospore: A conidium formed by budding along a hypha, pseudohypha, or single cell, as in yeast Chlamydoconidium/spore: An enlarged rounded conidium that is thick walled. May be located at the end of the hypha (terminal) or along the hypha (intercalary), singly or in chains. Arthroconidium/spore: Spores which develop by fragmentation of hyphae into short oblong rounded elements as in Geotrichum and Coccidioides. Asexual vegetative spores Cluster of blastoconidia single terminal chlamydospore Asexual aerial spores Sporangiospore – propagule that forms inside a sporangium which can be spherical or cylindrical. Occurs in hyphomycetes Conidiospore – spore formed at the tip of a conidiophore (specialized hyphae). Occurs in fungi imperfecti Conidiospores Macroconidium - large, multicellular thin or thick walled, spindle shaped conidiospore. Microconidium - small, unicellular conidiospores, usually formed along the hyphae singly or in clusters. Microsporum ,Trichophyton and Epidermophyton (No microconidia). Terminologies cont’d: Columella:  Enlarged dome shaped structure at the tip of a sporongiophore that extend into the sporangium Germ tube: (characteristic of Candida albicans) - Tubelike outgrowth from a conidium or spore; beginning of a hyphae Rhizoid: - Rootlike, branched hypha extending into the medium Septate: - Having cross walls Thallus: - vegetative body of a fungus Spherule: - Large round, thick-walled structure containing spores FUNGI Con’td:  fungi pathogenic to man and animals may show dimorphism  cell wall is composed of chitin.  can assimilate CO2 from the air as do plants  utilize preformed compounds as a source of carbon.  classified by their type (sexual or asexual) and arrangement of spores (ascus, basidium, conidium etc.). Classification of Fungi Based on taxonomy: 1) Ascomycetes eg. Blastomyces, histoplasma, microsporum, trichophyton, yeast genera including saccharomyces 2) Basidiomycetes eg. mushrooms 3) Zygomycetes eg. Rhizopus, mucor, absidia Classification of Fungi Based on clinical manifestations: Superficial Mycosis 1. Pityriasis versicolor 2. Tinea nigra Cutaneous Mycosis 1. Dermatophytosis 2. Candidiasis Subcutaneous Mycosis 1. Chromomycosis (Chromoblastomyc osis) 2. Phaeohyphomycosi s 3. Sporotrichosis 4. Maduromycosis Systemic Mycosis 1. Histoplasmosis 2. Blastomycosis 3.Coccidioidomycosis 4.Paracoccidioidmyc osis 5. *Penicilliosis (P. marneffei) and *Sporotrichosis Opportunistic Mycoses - Caused by endogenous or ubiquitous organisms of low inherent virulence that cause infection in debilitated, compromised patients Caused most commonly by: Candida, Cryptococcus, Aspergillus, Rhizopus, Mucor and Absidia Actinomycetes (true bacteria): - Diverse group of Gram positive bacilli  Form chains of filaments  Most are saprophytes that live in soil  Related to corynebacteria, mycobacteria, streptomycetes  Responsible for 3 human infections: Actinomycosis, nocardiosis and actinomycetoma The Epidemiology of Fungal Infections Infections divided into 2 categories: 1. Nosocomial: > acquired in a healthcare setting > almost always opportunistic 2. Community Acquired: > opportunistic mycoses > endemic mycoses - acquired by living in a geographic area constituting the natural habitat of a pathogenic fungus Epidemiology Cont’d: Seventh most common cause of infectious diseases over the past two and a half decades Factors contributing to increase fungal infections - immunosupressed or immunocompromised pts - a mobile and aging population with an increased prevalence of chronic medical conditions - use of new and & aggressive medical & surgical therapeutic strategies. Risk Factors: - Broad spectrum antibiotic  Cytotoxic drugs  Organ transplantation  Indwelling catheter  Extensive surgery or burns  Neutropenia  ICU stay  Haemodialysis  Malnutrition PATHOGENIC FUNGI FOR MAN A) Superficial Mycoses 1) Pityriasis versicolor B) Cutaneous mycoses 1) Dermatophytes 2) Candidiasis 1) Pityriasis versicolor (Liver spots) Aetiology – Malassezia furfur 2) Dermatophyes (Ringworm fungi) - Affect skin, nail and hair - structures with an abundance of keratin. These fungi are: Microsporum – skin and hair Trichophyton - skin, nail and hair Epidermophyton – skin and nail Dermatophytes Continued Diseases include: Tinea capitis - ringworm of scalp Tinea barbae - chronic folliculitis of beard, neck or face Tinea corporis - infection of glabrous skin Tinea manus - involves interdigital spaces and palmer surfaces of hand Tinea unguium - infection of nails Tinea cruris - infection of groin ( commonly called jock itch) Tinea pedis - infection of feet (commonly called athlete’s foot) Microsporum canis – septate hyphae with spingle shaped, rough and thick walled macroconidia (usually > 6 cells). Few microconidia Trichophyton mentagrophytes – Cigar shaped macroconidia ( not always present), septate and coiled hyphae, microconidia clustered on branched conidiophores. Epidermaphyton floccosum – septate hyphae with smooth, club shaped macroconidia (singly/clusters, 2-6 cells). No microconidia. 3) Candidiasis: - Pathogenic Yeast-like fungi, Endogenous infection - Include skin infections, nail infection, thrush, oesophagitis, enteritis, pneumonia, septicemia B) Subcutaneous Mycosis Diseases: - Sporotrichosis – Sporothrix schenckii - Maduromycosis (madura foot) – caused by a variety of fungi (Pseudallescheria boydii - most frequent agent) and bacteria (including species of Streptomyces, Actinomadurae, and Nocardia) - Chromoblastomycosis (granulomatous infection of skin) - cause by dematiaceous fungi Isolation and identification of pathogenic fungi cont’d. 3) Subcutaneous (Lab diagnosis) Sporotrichosis (Sporothrichum schenckii) > Microscopy - Organisms difficult to find - Asteroid bodies in tissues are considered diagnostic. > Culture - Dimorphic - 25 C (mould); at 37 C (yeast), tissues (yeast) > LFCB stain - Conidia in a typical rosette pattern Sporothrix schenckii – narrow septate hyphae and branching with tearshaped conidia (left 25-30 0C) , rosettelike cluster in young culture - Round, oval and fusiform budding cells of various sizes (right 37 0C, cigar bodies) 3) Subcutaneous cont’d (Lab. Diagnosis) Chromomycosis (several dematiaceous fungi) > Microscopy - Brown pigmented spherical sclerotic bodies (scrapings treated with KOH and in histological preparations) > Culture - Slow growing dematiaceous fungi - Organisms are identified according to the pattern and type of sporulation exhibited by the isolate. Fonsecaea pedrosoi Subcutaneous Treatment SPOROTRICHOSIS - Localized subcutaneous infection responds to orally administered potassium iodide. - Systemic manifestations of sporotrichosis may require itraconazole therapy. CHROMOMYCOSIS - Surgery and 5-fluorocytosine (5FC) are employed. - Results generally are unsatisfactory, particularly in advanced chronic disease. Subcutaneous Treatment MADUROMYCOSIS (Mycetoma) a) Actinomycotic Mycetoma Streptomycin or amikacin, co-trimoxazole or dapsone, or ciprofloxacin b) Eumycotic Mycetoma Prolonged antifungal therapy with itraconazole (10 months) can improve early lesions Antifungal chemotherapy with Amphotericin B for late, mutilating lesions. Surgical excision with amputation as a last resort. Isolation and identification of Systemic Mycoses 4) Systemic i) Histoplasmosis (Histoplasma capsulatum) > Direct microscopy (sputum, mucocutaneous lesions, biopsy, RES) Giemsa stain - intracellular yeasts with halo (macrophages) > Culture - dimorphic, tuberculate macroconidia (250C) > Serology - C.F.T, I.D. > Histoplasmin skin test ; +ve indicates exposure only Histoplasma capsulatum – septate hyphae and large round thick walled macroconidia (left 250C, tuberculate, projections) - Small round/oval budding cells (right, 370C) Isolation and identification cont’d. 4) Systemic cont’d ii) Coccidiomycosis (Coccidiodes immitis) > Microscopy - spherules with endospores (sputum) > Culture - arthrospores Confirmation - identification of arthrospores and their conversion to spherule in tissue culture or in animals > Serology - Skin test, C.F.T., I.D. Coccidiodes immitis – Spherules with endospores Isolation and identification cont’d. 4) Systemic cont’d iii) Blastomycosis (Blastomyces dermatitidis) > Microscopy - Typical thick walled, broad based, single budding yeast in sputum (eg. Stains-H&E; PAS; Mucicarmine; GMS) > Culture - Saboraud’s & Mycobiotic agar- dimorphism demonstrated Systemic cont’d Treatment Histoplasmosis - 10 pulmonary histoplasmosis and localized lung lesions do not require treatment Amphoteracin B > - progressive pulmonary disease and disseminated histoplasmosis Coccidiodomycosis - 10 coccidiomycosis resolves without treatment - Chronic pulmonary and disseminated coccidiodomycosis require Amphotericin B Paracoccidiodes brasiliensis - thermally dimorphic fungus distributed in Brazil and South America. Lesions due to Paracoccidioidomycosis on the face of a Brazilian child Systemic cont’d Treatment: Blastomycosis Amphotericin B – serious pulmonary disease Uncomplicated pulmonary disease – respond to itraconazole LABORATORY DIAGNOSIS 1) Specimens The specimens for laboratory diagnosis of fungus infections will depend upon the type of infection and may include: Skin scraping infected hair infected nail Dermatophytes Biopsy material Exudate (granulous or ulcerative lesions) Subcutaneous Sputum biopsy tissue Blood films bone marrow Systemic mycoses CSF Cryptococcus Swabs Monilia Other exudates Microscopic Examination Direct Microscopy  Wet preparation with saline (sputum, pus ) - Look for budding yeast cells, hyphae & pseudohyphae, conidia, granules, sperules  10% KOH preparation ( skin, hair, nail eg. Dermatophytes) - digest tissue elements (epithelial cells, leucocytes, debris)  India Ink preparation - Negative staining to observe capsule around yeast eg. Cryptococcus neoformans Stained preparations.  Gram stain - any fungal forms may be observed (eg. Yeast, C. albicans)  Acid fast stain - eg. Nocardia – partially acid fast  Lactophenol cotton blue - phenol in stain kills any organism while lactic acid preserves fungal structures - cotton blue stains the chitin in fungal cell wall (Slides prepared from culture)  Stained preparations con’td.  Gomori methenamine silver stain (GMS) Periodic acid-Schiff (PAS) Haematoxyllin & Eosin (H&E) CULTURE  Blood agar  Sabouraud’s Dextrose Agar (SDA) ( RT or at 370C)  Mycobiotic ( RT or at 370C)  Brain Heart Infusion Agar  Thioglycolate Broth  Others Serological Examination Largely performed in specialised centres e.g. C.D.C in Atlanta for the diagnosis of certain systemic mycoses. Examples of serological tests include: Immunodiffusion (ID)- precipitation Tube Agglutination – known killed antigen + serum Complement Fixation (CFT) Indirect Latex Fixation (ILA) Indirect fluorescent antibody (IFA) KOH preparation Brown-pigmented, round to polyhedral, thick walled sclerotic bodies