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Introduction Medical Mycology. General Fungi-1. Fungi eukaryotic microorganisms Larger than bacteria. They’re Essentially Aerobic. Mostly found in Nature living in association with plants. Many of them act as harmful organisms.
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General Fungi-1 Fungi • eukaryotic microorganisms • Larger than bacteria. • They’re Essentially Aerobic. • Mostly found in Nature living in association with plants. • Many of them act as harmful organisms. • Others free saprophytes –types of fungi utilize organic matter as an energy source like soil and rotten vegetables-on dead organic substances. • More than 100000 types. • Few associated with human diseases.
Fungi cell Structures • About 100 Fungi types are opportunistic pathogens. • Yeasts are part of normal florain Oral cavity-intestine-Vagina and they’re Opportunistic pathogens. • Few types like Cryptococcus neoformans–capsulated fungi and it’s antiphagocytotic- are true pathogens. • All are not susceptible to antibacterial drugs or phages. STRUCTURE: • Fungi Cell wall: composed Mostly of complex polysaccharides (chitin) with less amount of glucan and mannan (polysaccharides). • Cell membrane: lipid bilayer and it’s the innermost layer arround the fungal cytoplasmconsists of phospholipids, protein and Ergosterol. –ergosterol is te target of all antifungal agents, which work by disuptingergosterols either by binding to it and producing holes in the membrane or by interfering ergosterols synthesis./ resistance can be developed but much slower and it’s been recognized in candida- • Cytoplasm: contains true nucleus –eukaryotic-, microtubules composed of tubulin/Specific Protein, Mitochondria, Lipids & phosphate granules.
Fungi consist two major groups: • Yeasts: • (unicellular cells; 0.5-4 um). • develop large colonies on culture agar media. • Mostly reproduce asexually by budding one or more buds. • A few reproduce by binary fission. • When buds don’t separate they from long chains of yeast cells called Pseudohyphae. And this happens when it’s attached to our mucosa causing infections, so it’s pathogenic. • Baker's yeast: Saccharomycescerevisiae. it ferments glucose producing Co2 + alcohol which are very helpful in Production of Bread (baking), Vitamins, Biogenetic and in Medical drugs synthesis like Insulin. (Non-pathogenic)
2. Molds (filamentous Fungi) • composed of various cellular structures (Multicellular colonies) • Have different morphological types of Hyphae (filaments).Composed of clumps of interwind banching hyphae. • Extension of single spore (hypha cell) into branching nest of filamental cells.grow by longitudinal extension. (((Explanation of all above: it reproudce by spores which are hypha cells, these spores start to extend in longitudinal directions to form filaments –hyphae- and they got different morphological types because of interwinding of these hyphae in different shapes. And then the top of these hyphae produce sores once again upon exposure to oxygen))) Watch the first minute in this video and you’ll get the idea: http://www.youtube.com/watch?v=9kcKF8stsIM • reproduction by spores - the reproductive bodies of molds-, hyphae. • Single cells are up to 20um. • Growth in vitro gives you Aerial & Vegetative Mycelium Vegatative are the horizontal filaments which absorbs nutrients And support growth but Ariel is the portion of mycelium that grows upward or outward from the surface of the substrate, and from which propagative spores develop.
Filaments Fungi/ Molds Molds form multicellular filaments (hyphae) and could be non-septat or septat hyphae.((A hypha consists of one or more cells surrounded by a tubular cell wall. In most fungi, hyphae are divided into cells by internal cross-walls called "septa" (singular septum). Septa are usually perforated by pores large enough for ribosomes, mitochondri and sometimes nuclei to flow between cells. Some fungi have aseptate hyphae, meaning their hyphae are not partitioned by septa.)) • It produce spores of different sizes & structures, arrangement and color. • A mass of hyphae and spores is represented by Aerial & Vegetative Mycelium (as calrified in the previous slide) • Dimorphic Pathogenic fungigrow as Yeasts or Yeast-like structure in vivo at 37°C, but as in vitro as Molds 20 -40°C. • Lab Identification: Direct smear , Culture on Sabourauds dextrose agar or blood agar. • Slow rate varies from Slow to rapid growth (2-30 days). • Can be identified DEPENDING ON : Morphology, reproduction of ((spores/yeast cells/ Filments (Hyphae)), Colors of Micro/Macro Conidia (SPORES), Arrangement of spores on vertical hyphae /aerial mycelium , Hyphae with or without septa / single septum AND type and color of spores. • No specific antibodies/ serological tests
Growth of Fungi • Fungi have chemoheterotrophic metabolisms which means obtaining nutrients and energy through decomposing complex organic materials and Plants biomass -The mass of organic material produced by living organisms.-into small molecules & basic elements. • Require water/ moist, carbon source & various minerals for growth • Certain type of fungi called mushrooms can be used as food and have high nutritional value (Minerals)and Some of mushrooms produce Antibiotics. • Fungi contaminate most types of food and may cause fatal disease. • Few Fungi produce mycotoxins, which is the fungal toxin. One type of molds can produce many types of mycotoxin and one type of mycotoxin can be produced by many types.
Growth in Human tissues • Pathogenic Yeasts :produce often elongated oval cells & Pseudohyphe on body mucosal cells when attached to it, causing Mild inflammationand cause erythematic lesions - Redness of the skin caused by dilatation and congestion of the capillaries- • Pathogenic Molds: single and multiply filaments. cell fragments in infected tissue and Rarely form spores. Causes Superficial lesions without inflammation. They multiply filaments not spores because spores need high amount of oxygen which is not found inside the body • Antifungal drugs: Nystatin, Fluconazol, Amphotericin B, Casbofungin . All react with ergosterol forming compmex molecules and damage cell membrane.
Capsulated Yeast / Cryptococcus neoformans (India ink test) this test can make the capsule visualized
Human Mycosis-1 Dermatophytosis (Superficial Mycoses/ CutaneousMycoses) • Dermatophytes: category of cutaneous fungal infections and the most common dermatophytes include : Trichophyton, Microsporiumand Epidermophyton. • Include many species distributed Worldwide. • Grow by Spores, Hyphaefragments. • Transmitted to human, animals & environment. CAUSES MANY INFECTIONS LIKE: • Ringworm / Tineacorporis: A superficial dermatophyte infection characterized by either inflammatory or non-inflammatory lesions on skin , Erythematic lesion cause Allergic reaction. Involve superficial keratinize/Dead tissue like skin, hair, Nails. –the fungi spread frorming a ring shaped with a red raised border, the border is the inflamation and the center is healing.- All dermatophytes can cause similar skin lesions
Human Mycosis-3 2. Tineacapitisin Hair:infected Hairshaft /hair follicles and Scalpفروة الرأسeither Endothrix(invades hair shaft) or Exothrix(infects hair surface). • Composed of large number of spores and sticky material. • Common in Childrenand Rare in Adults. • Infection spread rapidly by contact with infected hair (Outbreaks in schools.) 3. TineaunguiumIn Nails 4. Tineapedis قدم الرياضي in Feet fingers & interspaces between fingers. They’re moist skin lesions. Common in Adults, and can develop to chronic lesion and it’s difficult to cure. It requires moist and warmth, so happens mostly with those wearing shoes. • Causative agents:Mostly Epidermophyton species. Less Trichophyton & Microsporiumspecies
Tineaversicolor(Pityriasisversicolor)caused by Malasseziafurfuris a common lipophilic yeast, part of normal skin floraand Lives on oils and fats. Mostly causes endogenous infection.very common among young adults. • Clinical Features: Discoloration (hyper/ hypo pigmentation skin spots on face, armsor any body site) Rarely erythematic skin lesions, causes Allergic reaction and Skin scaling. Activated by various factorslike stress conditions, fever, warm & humid environment. • Diagnosis:Clinical picture, Direct smear spherical & thin filaments yeast (it’s only diagnosed by filaments). There’s Difficulty in isolation, cultivation & identification. Mostly Self-limited 1-3 weeks
Yeast /Candida species • Candidiasis/ Candidiosis: mostly C. albicans (50-70%) and Less C. glabrata, C. tropicalis., C. Krusei & Others spp. • Part normal body Flora in Mouth(oral cavity), Vagina, Skin, Intestine, Urinary tract. • Opportunistic Pathogens: mostly endogenous infection, arising from 1) overgrowth of the fungus 2)Radiation 3) Toxic drugs 4) intensive use of antimicrobial drugsso we Inhibiting normal flora and Candida activated (Underlining diseases), it causes different or more severe infections in immunocompromisedhost.(like systemic infections) • Exogenous infection : transmitted from catheters or prosthetic devices or Respiratory tubesor person-to-person transmission, causes Common Nosocomial Infection. • Clinical Features: • oral thrush mucosa(patches of creamy white exudates with reddish base over the mucose), Throat- Pharynx, can transmitted to Lung. • vaginal Candidiasis : discharge & Irritation. • Candidemia, meningitis. (in immunocompromised patients)
Candida Pseudohyphae ( Chlamydo-Blastospores)-Blastospores is dimorphic-
Other Yeast Infection • Encapsulated C. neoformans:Large Capsule, causes a chronic- subacute- acute pulmonary infection, May spread to blood, CNS and causes systemic disease or meningitic disease. Often isolated from pigeon, Birds excreta. • C. neoformanshas a world-wide distribution. Now it’s one of the most significant opportunistic pathogens in humans. Most cases are identified in immunodifficient and AIDS patients. Like ¾ of the cases.
Mold infection:Aspergillosis-1 • Aspergillus speciesare common in nature, Spores spread with dust particles anf we uptake it by Inhalation. • Few develop Allergy or clinical disease • A. fumigatus, A. flavus, A. niger. • Causes CommonHuman Aspergillosis 1- Allergic Bronchopulmonary Aspergillosis: caused by the Presence of conidia(spores) or transient growth of the organism in body, causing Respiratory tract infection associated with Granuloma ,allergic reaction, eosinophilia,Lung Asthma, Nose/Sinusitis and Ear/Otitis externa (Otomycosis) which is often associated with swelling, pain & black discharge.
Aspergillosis-2 2- Pulmonary lesions in preformed cavities (Aspergilloma) and debilitated tissues. – people with lung cavitations like in TB develop this disease- • Common in Tuberculosis & Lung carcinoma patients. • Can grow aspergillus fungal ball in the cavity and requires a surgical removal • fatal. • And causes Localized Lesions: in Eyes, Sinuses, External Otitis infection treated by Surgery & Antifungal Treatment. ---------------------------------------------------------------------------------------------------------- • Fungi produce toxins called Mycotoxicosis: Worldwide million cases due to ingesting contaminated foods with mycotoxin-talked about it previously-. Mostly mild gastrointestinal symptoms and caused by various fungi. The toxin that is produced by Aspergillosis(A. flavus) is called Aflatoxins. And it’s fatal. • Few micrograms of aflatoxin cause acute Liver cirrhosis, Edema & hemorrhage in lung kidneys, coma & Death. • Found common in :Grains, Peanuts, Ground nuts, Rice, Milk Powder, Due to storage food under bad not dry condition.
