number Done by Corrected by Doctor د.حامد الزعبي

Transcription

1 number Fungi#1 Done by نرجس الس ماك Corrected by مهدي الشعراوي Doctor د.حامد الزعبي

2 Introduction to Mycology -Terms: -Medical Mycology: The study of mycosis and their etiological agents -Mycosis: Disease caused by fungi (less than 300/200,000 species are pathogenic) -Fungus (kingdom of fungi):- 1-Eukaryotic: True nuclei, doesn't contain chlorophyll 2-Produces filamentous structures (hyphae) 3-Produces spores (sexual & asexual reproduction) -Divided into: A- Saprophytic: Lives and feed on dead tissue (plays a role in decomposition and nutrient cycling) B- Parasitic (feeds on living organisims) 5-Requires an organic source of carbon associated with decaying matter 6-Cell wall consists of polysaccharides (Chitin, β-glucan) which is the site of action for Anti-fungal drugs 7-Cell membrane consists of Ergosterol which is also the site of action for Antifungal Drugs 8-Most fungi are obligatory aerobes. -Importance of fungi: 1-A common cause of damage to crops and food chain

3 2-Few species of fungi cause diseases in humans (300/200,000) *Fungal infections are increasing due to AIDS and immunosuppressant conditions 3-Production of antibiotics e.g: penicillin Fungi can be classified morphologically and according to the growth forms to: Yeast Filamentous fungi Dimorphoic fungi 1-Oval or round cells that reproduce by budding 2-Forms pseudohyphae(chains of elongated budding cells) 3-Common in immunocompromised patients (opportunistic fungi), can cause multisystem infections such as meningitis, arthritis and respiratory infections. 4-Ex: -Candida albicans (found normally in the intestinal tract) -Creptococcus neoformans (found in the soil and pigeon feces, commonly infects lungs initially) 1-Branching tubular filaments (hyphae) which may be separated or non-separated 2-Form mycelium: mass of branching, interlinking hyphae 3-Produce asexual spores at the tip or side of hyphae -Asexual spores may be contained in sac called Sporangiospores 5-Ex: -Zygomycetes -Aspergillus -Dermatophytes -Found in 2 forms: 1-Yeast At 37 C 2-Filamentous At 22 C -Ex: -Blustomycesdermatitidis -Coccidiodesimmitis -Histoplasmacapsulatum Fungal diseases: -Recently emerged as a growing threat to human health especially for immunocompromised patients

4 1-Fungal allergies: -Molds grow on any damp organic surface, and its spores are constantly in the air (airborne) -Inhaled and volatile fungal toxins may play a role in producing allergic manifestations such as asthmatic reaction (rapid broncho-constriction by IgE ) and eosinophilia -Ex: Aspergillus fumigatus (widespread fungi in the nature, readily become airborne that cause diseases in immunocompromised) 2-Fungal toxins (mycotoxicosis): -Under favorable conditions of temperature and humidity these fungi grow on certain foods, resulting in production of Aflatoxins *Most contamination has been encountered in tree nuts, peanuts and other oilseeds including corn 1- Alflatoxins: are group of structurally related toxic compounds produced by certain strains of fungi (Aspergillusflavus, parasiticus) 2- Alflatoxicocsis: poining condition and it result from ingestion of Alflatoxins in contaminated food 3- Alflatoxins: are metabolized in the liver to epoxide which is potent carcinogenic 4- Alflatoxin B1 induce mutation in the P53 human suppressor gene leading to loss of growth control in hepatocyte *P53: protein in the body that triggers apoptosis by stimulating Bax and Bak, stops the formation of tumors ( Patho slide 5 dr.heyam ) 3-Fungal infections (mycoses): -Fungal infections range from superficial up to Overwhelming infections that are rapidly fatal in compromised patients -Fungal infections are increasing due to increasing use of antibiotics, corticosteroids and cytotoxics drugs (immunosuppression)

5 Fungal infections Superficial Subcutaneous Systemic mycoses Infection involve the 1-skin 2-mucus membrane 3-nail or hair without tissue destruction 4-immunological reaction: -cutaneous candidiasis -dermatophtys -infection is confined to subcutaneous tissue without dissemination -Primarily pulmonary lesion that may disseminate to any organ -Subdivides: -pathogenic fungi -opportunistic fungi -Diagnosis: -The diagnosis of fungal infections is based on a combination of clinical observation and laboratory investigation -The first indication of systemic mycosis is the failure to respond to Antibacterial Drugs -Laboratory diagnosis: -Depends on: 1- Recognition of the pathogen in tissue by microscopy 2-Isolation of the causal fungus in culture 3-The use of serological tests 4-detecion of fungal DNA by PCR -Types of specimen: 1-Skin scales 2-Nail clipping

6 3- Scrapings of the scalp that include hair stubs 4-Swab from the mucous membranes in suspected Candida infection (sent To the lab in a ''clear'' transport medium) 5-Scrapings and crust, aspirated pus and biopsies in subcutaneous infection 6- In suspected systemic infection Specimens should be taken from appropriate sites *Skin scales and scrapings of the scalp are the most suitable specimens for diagnosis of ringworms *The specimens are collected into folded paper squares for transport to the laboratory -Direct microscopy: -Most specimens can be examined satisfactorily in wet mount after partial digestion of the tissue with 10-20% potassium hydroxide (KOH) -To enhance the detection of fungi add calciflour white and use fluorescence microscopy (fluorescent hydroxide- Calcofluor binds to the fungal cell wall) -Special stains are used -Culturing: -Most of pathogenic fungi are easy to grow in cultures. -Ex: Sabouraud dextrose medium: -Commonly used -Supplemented with: 1-chloramphenicol to minimize bacterial contamination 2-cycloheximide to reduce contamination with saprophytic fungi -Anti-fungal therapy: -Antibiotics have no effect on fungal infections -The action of the Anti-fungal depends on the presence of chitin(cell wall) and ergosterol (cell membrane)

7 -Amphotercin B and Nystatin are Polynes (fungicidal), various Azeles (fungistatic) are commonly used for treatment of fungal infection Anti-fungal types: 1-Polyene derivatives -Amphotericin -Nystatin 2-Azoles -Ketoconazole -Fluconazole -Itraconazole -Voriconazole -Posaconazole 3-Griseofulvin 4-Allylamines -Terbinafine (lamasil) 5-Echinocandins -capofungin 6-5-fluorocytosine