Fungi of Medical Importance 2022 PDF

FUNGI OF MEDICAL IMPORTANCE Dr Lorina Badger-Emeka COM – KFU INTENDING LEARNING OUTCOMES Students should be able to: 1. describe the structure of a fungal cell 2. Enumerate the major differences between fungi and Bacteria 3. differentiated between fungi and bacteria...

FUNGI OF MEDICAL IMPORTANCE Dr Lorina Badger-Emeka COM – KFU INTENDING LEARNING OUTCOMES Students should be able to: 1. describe the structure of a fungal cell 2. Enumerate the major differences between fungi and Bacteria 3. differentiated between fungi and bacteria 4. Know the differences between molds and yeast 5. know the reason why fungi sporulate 6. classify human mycoses  INTRODUCTION Moulds and Yeasts are widely distributed in the air, dust, fomites and normal flora Fungi are usually non-pathogenic But they are mostly plant pathogens Humans are relatively resistant Of the 100,000 species known only 300 have been linked to diseases in animals  Introduction cont’d They represent a diverse group of organisms Saprobes (living on dead and decaying matter) Symbionts (a mutual association between two organism) Commensals (a relationship between 2 organisms in which one benefits and the other neither benefits nor is harmed) Parasites (association where the host is harmed and the other organism benefits).  Causes of Fungal infections You don't catch yeast infections. The yeast is already there. Overgrowth of yeast can result from: Antibiotic use, which leads to a change in the pH that allows yeast to overgrow Pregnancy Uncontrolled diabetes Impaired immune system Anything that changes the type and amount of bacteria normally present in any part of the body.  Structure of fungi Fungi can exist as unicellular forms [Yeast] reproducing asexually Or as filamentous forms [molds] reproducing both sexually and asexually Most fungi exist as either yeast or molds Some can however exist as either form of morphology (Dimorphic).  Structure of fungi cont’d Fungi can exist as unicellular forms [Yeast] reproducing asexually Structure of fungi  General structure of a fungal cell They are distinguished from other eukaryotes by having a rigid cell wall. The cell wall composes of chitin and glucan. Next to the cell wall is the cell membrane  Fungi and bacteria differences Fungi Bacteria Have complex cellular structure Prokaryotic They exits either in a unicellular form (Yeast) with asexual Single cell multiplication No nuclear membrane Or in a filamentous form (mold) that can replicate sexually and Rapid reproduction asexually. Well defined nucleus and cytoplasmic organelles Slow growing  Molds and Yeast Similarities Both yeast and molds are fungi They are both Eukaryotic fungi Both are considered as parasites Differences between molds and yeast  Courtesy Murray et al., 9th Ed. pg. 573 YEAST They are unicellular organisms Multiplying by binary fission and budding Fungal cell morphology. (A) Yeast cells reproducing by nuclear fission and by blastoconidia formation. The elongation of budding yeast cells to form pseudohyphae is shown, as is the formation of a germ tube.  Courtesy Murray et al., 9th Ed. pg. 573 Fungal cell (B) Types of hyphae seen with various molds. morphology. Examples of asexual spore formation and associated structures seen with a (A) Mucorales and an (B) Aspergillus spp. Courtesy Murray et al., 9th Ed. pg. 574 Molds They are multicellular organism that grow in a form called hyphae Some are used in the production of antibiotics. E.g., Penicillin and Cephalosporins Rapid growth They grow in the form of cytoplasmic filaments or hyphae that make up mycelium Consist of aerial hyphae, & vegetative hyphae Reproduction by spore formation either sexually or sexually on the aerial hyphae Why do fungi sporulate? Sporulation of fungi usually occurs under suitable nutritional and aerational conditions Spores are produced during sexual or asexual reproduction. Purpose of Sporulation??? Dispersal. This helps in transporting small portions of the fungus to a large geographic area. Question: Why might this be important? Why do fungi sporulate? cont’d Answer: Preservation - Some spores preserve the potential for growth at the same site because they provide a means by which the fungus can survive unfavourable environmental conditions, Genetic variation - sexual sporulation provides the potential for genetic variation. CLASSIFICATION OF HUMAN MYCOSES Fungal infections may be classified according to: the tissue infected The specific characteristics of the organisms group Inclusive of which are; superficial, cutaneous and subcutaneous mycoses The endemic mycoses and the opportunistic mycoses  Superficial Mycoses They are infections limited to the very superficial surfaces of the skin and hair They are nondestructive and are of cosmetic importance only. Cutaneous Mycoses CLASSIFICATION OF HUMAN MYCOSES cont’d Cutaneous Mycoses These are infections of the keratinized layer of the skin, hair and nails The infection might elicit a host response, becoming symptomatic Examples are Candida spp. And Aspergillus spp. Classification of Human Mycoses cont’d Subcutaneous Mycoses: Involves the deeper layers of the skin, cornea, muscles, connective tissue etc. Endemic mycoses: They are often referred to as systemic mycoses because the organisms are true pathogens and can caused infection in healthy individuals they produce primary infections in the lungs and subsequently to other organs and tissues Opportunistic Mycoses: caused by fungi that are normally commensals Question Which one of the following describes the microscopic filament of fungi A. Spirogyra B. hyphae C. filamentous algae Answer B Questions Which of the following describes the fungi group? A. Eukaryotic B. Diatoms C. prokaryotic Answer A Summary Lecture has looked into Fungi group The structural diversity and those of clinical importance Molds and yeast, similarities and differences between them, yeasts are usually unicellular; reproduce by budding or by fission; and produce round, pasty, or mucoid colonies on agar. Molds, on the other hand, are multicellular organisms consisting of threadlike tubular structures, called hyphae Google images The most common fungal infection Questions??  References Medical Microbiology By Patrick R. Murray; et al., 9th Edition, Section 6. pg 572 - 577