Clinical Mycology

Distribution of microorganisms Air Soil Water Animals Human body

3 Microbes are involved in nutrient production & energy flow decomposition production of foods, drugs & vaccines bioremediation causing disease

Microorganisms and Human Beings Beneficial activities: Most microbes are of benefit to human beings, some are necessary( nitrogen, carbon cycles, etc) Harmful activities: A portion of microbes cause diseases and are poisonous to human, and these are really that concern us in the study of medical microbiology, etc.

5 Impact of pathogens Nearly 2,000 different microbes cause diseases 10 B infections/year worldwide 13 M deaths from infections/year worldwide

6 Characteristics of microbes

Archea Bacteria Eukaria DomainKingdom Planta Animalia Mycota (Mycetae) Classification of Fungi

Comparison of fungi and bacteria featurefungibacteria diameter4um1um nucleusEukaryoticprokaryotic cytoplasmMitochondria and endoplasmic reticulum present Cell membraneSterols presentSterols absent Cell wallchitinpeptidoglycan sporesSexual and asexual spores for reproduction Endospores for survival, not for reproduction Thermal dimorphism yesNo metabolismRequire organic carbon; no obligate anaerobes May do not require organic carbon; many obligate anaerobes

Characteristics of fungi A. eukaryotic, non- vascular organisms B. reproduce by means of spores (conidia), usually wind- disseminated C. both sexual (meiotic) and asexual (mitotic) spores may be produced, depending on the species and conditions D. typically not motile, although a few (e.g. Chytrids) have a motile phase. E. like plants, may have a stable haploid & diploid states F. vegetative body may be unicellular (yeasts) or multicellular moulds composed of microscopic threads called hyphae. G. cell walls composed of mostly of chitin and glucan.

More Characteristics of Fungi H. fungi are heterotrophic ( “other feeding,” must feed on preformed organic material), not autotrophic ( “self feeding,” make their own food by photosynthesis). - Unlike animals (also heterotrophic), which ingest then digest, fungi digest then ingest. -Fungi produce exoenzymes to accomplish this I. Most fungi store their food as glycogen (like animals). Plants store food as starch. K. Fungal cell membranes have a unique sterol, ergosterol, which replaces cholesterol found in mammalian cell membranes L. Tubule protein—production of a different type in microtubules formed during nuclear division.

Dimorphism Many pathogenic fungi are dimorphic, forming moulds at ambient temperatures but yeasts at body temperature.

Structure of fungi

Morphology Unicellular fungi Multicellular fungi Hypha: mycelium (vegetative, aerial or reproductive). Spores: asexual spore a) Conidium: macroconidium, microconidium. b) Thallospore: blastospore, chlamydospore, arthrospore c) Sporangiospore

Fungal Morphology Yeast Hyphae (threads) making up a mycelium Mould Encapsulated yeast Cryptococcus neoformans

Multicellular fungi Hypha spore

Hypha

Medically important fungi Includes 4 phyla Ascomycota Sexual reproduction in a sack called an ascus with the production of ascopspores. Basidiomycota Sexual reproduction in a sack called a basidium with the production of basidiospores. Zygomycota Sexual reproduction by gametes and asexual reproduction with the formation of zygospores. Mitosporic Fungi （ Fungi Imperfecti) ， No recognizable form of sexual reproduction. Includes most pathogenic fungi.

Dimorphism

Germ theory of disease Many diseases are caused by the growth of microbes in the body

23 Robert Koch Established a sequence of experimental steps to show that a specific m.o. causes a particular disease. Developed pure culture methods. Identified cause of anthrax, TB, & cholera. ( )

Koch’s postulates The microbe must be found in the body in all cases of the disease It must be isolated from a case and grown in a series of pure culture in vitro It reproduce the disease on the inoculation of a late pure culture into a susceptible animal The microbe must be isolated again into pure culture from such experimentally caused infection.

25 Taxonomy - system for organizing, classifying & naming living things Domain - Archaea, Bacteria & Eukarya Kingdom - 5 Phylum or Division Class Order Family Genus species

Culture Sabouraud culture medium optimal pH 4-6 optimal temperature C some deep pathogenic fungi need 37 C, Aerobic types of colonies– yeast, filamentous Multiplication:budding, hypha formation, branching or disruption of hypha, spore formation

Resistance Resistant to dry, sunlight, UV light and many chemicals Sensitive to wet heat

four types of mycotic diseases: Hypersensitivity - an allergic reaction to molds and spores. Mycotoxicoses - poisoning of man and animals by feeds and food products contaminated by fungi which produce toxins from the grain substrate. Mycotoxin and tumor Mycetismus - the ingestion of toxin (mushroom poisoning). Infection

Immunity Nonspecific immunity Specific immunity

DIAGNOSIS 1. Skin scrapings suspected to contain dermatophytes or pus from a lesion can be mounted in KOH on a slide and examined directly under the microscope. 2. Skin testing (dermal hypersensitivity) used to be popular as a diagnostic tool. 3. Serology may be helpful when it is applied to a specific fungal disease. 4. Direct fluorescent microscopy. 5. Biopsy and histopathology. 6. Culture. Pathogenic fungi are usually grown on Sabouraud dextrose agar. It has a slightly acidic pH (~5.6); cyclohexamide, penicillin, streptomycin or other inhibitory antibiotics are often added to prevent bacterial contamination and overgrowth.