PHARMACEUTICAL MICROBIOLOGY I PHT 226 Dr. Rasheeda Hamid Abdalla Assistant Professor com

GENERAL PROPERTIES OF FUNGI

OBJECTIES  Fungal Infection  Pathogenic Fungi Characteristic structures Habitat and Nutrition Modes of Fungal Growth Sporulation

Fungi The fungi are a diverse group of saprophytic and parasitic eukaryotic organisms Fungi can be distinguished from other infectious organisms such as bacteria or viruses because they are eukaryotes (they have membrane –enclosed nucleus). Kingdom:Mycota -Of the some 100,000 fungal species only about 100 have pathogenic potential to humans Human fungal diseases (Mycoses) are classified by the location or in the body where the infection occurs:

Fungal Infection  Cutaneous : when the infection limited to the epidermis  Subcutaneous when the infection penetrates significantly beneath the skin  Systemic when the infection is deep within the body or disseminated to internal organs  Systemic mycoses can be divided into:  Caused by true pathogenic fungi capable of infecting healthy individuals

Fungal Infection  Opportunistic,infecting primarily individuals who have predisposing conditions such as immunodeficiency or debilitating diseases (diabetes, leukemia, etc..) Fungi produce and secrete a variety of unusual metabolic products, some of which when ingested, are highly toxic to humans and animals. Thus fungi can cause poisoning as well as infections Fungal spores are important as human allergenic agents

Pathogenic Fungi 1-True pathogen: A-cutaneous infective agents Epidermophyton species Microsporum species Trichophyton species B-Subcutaneous infective agents Actinomadura madurae Cladosporium Madurella grisea Phialophora Sporothrix schenckii

Pathogenic Fungi C-Systemic infective agents Blastomyces dermatitidis Coccidioides immitis Histoplasma capsulatum Paracoccidioides brasiliensis

Pathogenic Fungi 2-Opportunistic pathogens Absidia corymbifera Aspergillus fumigatus Candida albicans Cryptococcus neoformans Pneumocystis jirovecii

Categorization of fungi depend on 1)Characteristic structures 2)Habitats 3)Mode of growth 4)Reproduction

Characteristic structures  Cell wall and membrane components: -It composed largely of chitin, a polymer of N-acetylglucosamine, rather than peptidoglycan which is the characteristic component of bacterial cell walls Fungi are therefore unaffected by antibiotics (penicillin) that inhibit peptidoglycan synthesis

Characteristic structures The fungal membrane contains ergosterol rather than the cholestrol found in mammalian membranes. These chemical characteristics are useful in targeting chemotherapeutic agent against fungal infections.

Mechanism of Action of Antifungal Amphotericin B and Nystatin bind to ergosterol present in cell membranes of fungal cells.there they form pores that disrupt membrane function, resulting in cell death. The imidazole antifungal drugs (clotrimazole, ketoconazole, miconazole) and triazole antifungal agents (fluconazole and itraconazole) interact with C-14 α -demethylase to block demethylation of lanosterol to ergosterol Ergosterol is a vital component of the cell membrane of fungi,and disruption in it is biosynthesis result in cell death.

Habitat and Nutrition All fungi are heterotrophs (they require some performed organic carbon source for growth) They depend upon transport of soluble nutrients across their cell membranes -To obtain these soluble nutrients,fungi secrete degradative enzymes (for example, cellulose, proteases nucleases,etc) into their immediate environment. -This ability that enables fungi to live saprophytically on organic waste The natural habitat of almost all fungi is soil or water containing decaying organic matter

Modes of Fungal Growth Most fungi exist in one or two basic morphologic forms: 1)Filamentous mold 2)Unicellular yeast However, some fungi are dimorphic (that is,they switch between these two forms in response to environmental conditions)

Filamentous (mold-like) fungi The vegetative body, or thallus, of the mold –like fungi is typically a mass of threads with many branches, resembling a cotton ball This mass is called a mycelium, which grows by branching and tip elongation. The thread called hyphae,are actually tubular cells that,in some fungi, are partitioned into segments (septate), whereas in other fungi the hyphae are uninterrupted by cross-wall (non-septate) even in septate fungi

Yeast- like fungi These fungi exist as population of single,unconnected, spheroid cells They are some ten times larger than typical bacteria cell yeast-like fungi reproduce by budding Some fungal species,especially those that cause systemic mycoses,are dimorphic,being usually yeast-like in one environment and mold –like in another. Example of conditions that affect the choice of morphology are temperature and carbon dioxide levels

Sporulation Sporulation is the principal means by which fungi reproduce and spread through the environment Fungal spores are metabolically dormant, protected cells, released by mycelium in enormous numbers They can be borne by air or water to new sites, where they germinate and establish colonies Spores can be generated either asexually or sexually

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