clinical mycology. distribution of microorganisms air soil water animals human body
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Clinical Mycology
Distribution of microorganisms
Air
Soil
Water
Animals
Human body
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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.
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Impact of pathogens
Nearly 2,000 different microbes cause diseases
10 B infections/year worldwide
13 M deaths from infections/year worldwide
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Characteristics of microbes
Archea
Bacteria
Eukaria
Domain Kingdom
Planta
Animalia
Mycota
(Mycetae)
Classification of Fungi
Comparison of fungi and bacteriafeature fungi bacteria
diameter 4um 1um
nucleus Eukaryotic prokaryotic
cytoplasm Mitochondria and endoplasmic reticulum present
Mitochondria and endoplasmic reticulum present
Cell membrane Sterols present Sterols absent
Cell wall chitin peptidoglycan
spores Sexual and asexual spores for reproduction
Endospores for survival, not for reproduction
Thermal dimorphism
yes No
metabolism Require 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 fungiMulticellular 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 yeastCryptococcus neoformans
Multicellular fungi
Hypha
•spore
Hypha
Unicel lular fungiUnicel lular
fungi
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.
Deutemycotina
Ascomycotina Basidiomycotina
Zygomycotina
Dimorphism
Germ theory of disease
Many diseases are caused by the growth of microbes in the body
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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.
(1843-1910)
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.
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Taxonomy - system for organizing, classifying & naming living things
Domain - Archaea, Bacteria & EukaryaKingdom - 5Phylum or DivisionClass OrderFamilyGenusspecies
Culture
Sabouraud culture mediumoptimal pH 4-6optimal temperature 22-28 C some deep pathogenic fungi need 37 C, Aerobictypes of colonies– yeast, filamentousMultiplication: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 tumorMycetismus - the ingestion of toxin (mushroom poisoning).
Infection
Immunity
Nonspecific immunitySpecific immunity
DIAGNOSIS1. 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.
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