Mycology Week 1

5 types of microorganisms

helminth, virus, protozoan, bacterium, fungus

nomenclature

Genus species

Symbiotic Relationships

mutualism, commensalism, parasitism

mutualism

both partners benefit, example: intestinal bacteria help synthesize vitamins K and B

commensalism

one partner benefits while the other is unaffected, example: barnacles on whales, flora living on skin

parasitism

one partner benefits at the expense of the other, example: fungi that infect and feed on host organisms, pathogenic infection

anatomical barriers as ecosystem

the skin and mucous membranes are anatomical barriers to infection, but they also give a foundation for microbial ecosystems that support beneficial microbial communities.

normal microbiota (flora)

populations of microbes that are routinely found growing in/on a healthy personand play essential roles in digestion, immunity, and preventing pathogenic infections. They help maintain homeostasis in the host.

resident flora

populations of microbes that permanently inhabit a specific area of the body, contributing to health and immune function. it can change with diet, age, antibiotic use, stress, illness, and environemental factors

transient flora

form short associations and are replaced

sterile body fluids

CSF, pleural fluid, peritonial fluid, synovial fluid, pericardial fluid, blood, bone and marrow, urine in the bladder

protectie role of normal microbiota

covering binding sites for pathogenic attachment, consumption of available nutrients, producing toxic compounds like antibiotics

infection

when a microbe has a parasitic relationship with the host. sometimes the host doesn’t always notice symptoms (asymptomatic/subclinical)

infectious disease

when an infection results in disease

symptoms

felt by the patient, examples: pain and nausea

signs

observable effects through examination, examples: rash, pus, swelling

colonization

when a microbe can successfully establish on a host and grow, but it does not automatically mean there will be disease or infection

primary infection

the initial disease that may occur after infection

secondary infection

can happen as a result of a primary disease, example: secondary bacterial pneumonia can occur after an influenza infection

pathogen

a microbe that can cause disease in an otherwise healthy person

opportunistic pathogen

a microbe that causes disease when the host’s immune system is down, can be a part of the normal flora or a common microbe

true pathogen

microbes that cause disease in healthy people

virulence

describes how capable a pathogen is at causing disease, highly virulent means they have high pathogenicity

transmissible or communicable disease

can be spread from host to host, or indirectly through a vector

infectious dose

the minimum number of organisms required to establish infection

incubation

time between the introduction of a microbe and the onset of symptoms

illness

after incubation, signs and symptoms occur

convalescence

recovery, but the host may still be contagious

acute illness

rapid onset of symptoms that last a short time, immunity is established after, examples: common cold, flu, pneumonia, bronchitis, strep throat, UTIs

chronic illness

symptoms develop slowly and persist, examples: HIV/AIDS, hepatitis C, chronic kidney disease, heart disease, rheumatoid arthritis

latent illness

the infection never goes away and can be reactivated later in life, example: shingles, herpes, HIV, hepatitis B (HBV)

Koch’s Postulate

how to prove that a certain pathogen is the cause of a disease.

1. the microbe must be present in every case

2. the microbe must be isolated as pure culture from the diseased host

3. the same disease must occur when introduced to a susceptible experimental host

4. the microbe must be recovered from the experimental host

virulence factor

anything that a microbe produces that allows it to cause disease by infection, examples: toxins, enzymes, surface structures

molecular Koch’s Postulate

1. virulence factor should be found in pathogenic strain

2. a cloned virulence gene should make a non-pathogenic strain become pathogenic, and disrupting the virulence gene should reduce pathogenicity

3. virulence genes have to be expressed during disease

4. antibodies and immune cells against virulence gene should be effect at disrupting disease

mechanisms of pathogenicity

ways that pathogens are able to evade the immune system, examples: attaching to host cells, intracellular survival, invasion, toxin production, immune evasion (capsules or antigenic variation)

fungi

eukaryotic, single-celled or multinucleate organisms, eat through decomposing and absorbing organic material in which they grow

types of fungi

yeast, mold, mushrooms

clinical mycology overview

1. identification of pathogenic fungi

2. cultures are held for 4 weeks

3. macroscopic and microscopic observations are done

macroscopic observations of fungi

growth rate, colony structure, surface and reverse color

microscopic observations of fungi

1. lactophenol cotton blue staining to observe hyphae, spores, phialides, budding yeast

2. KOH prep to make fungi more observable

3. india ink for cryptococcus (can’t penetrate the capsule)

yeast overview

1. unicellular

2. budding

3. white and round colonies

4. found on fruit or skin

5. used for alcohol and baking

6. can cause infections

mold overview

1. has multicellular filaments (hyphae)

2. can make sexual or asexual spores

3. fuzzy colonies with many differing colors

4. found in dark humid places

5. cheese production

6. antibiotic production (penicillium)

7. can cause allergic reactions and respiratory illness

yeast budding

1. bud = blastospore

2. pseudohyphae = long chains of blastospores that are attached

3. bud scars form

mycelium

the root-like structure of fungi, made up of thin branching filaments called hyphae

mushroom

when conditions are right mycelium can form fruiting bodies which are referred to as the mushroom

vegetative mycelium

non-reproductive part of mycelium that grows underground or in organic matter to absorb nutrients

aerial mycelium

reproductive and asexual spore-forming, it grows above the substrate surface

hypha

a long, branching filamentous cell, many hyphae make the mycelium, it is the basic cellular unit of filamentous fungal structures

classification of hyphae

1. septate or nonseptate

2. morphology: nodular, root-like (rhizoid), racquet, pectinate, or spiral

what type of hyphae is this

nodular

what type of hyphae is this

rhizoid

what type of hyphae is this

racquet

what type of hyphae is this

pectinate

what type of hyphae is this

spiral

dimorphic fungi

a type of fungi that can exist as either mold (filamentous form) or yeast, typically depending on temperature, carbon dioxide, or nutrients

thermal dimorphism

pathogenic fungi that change form based on temperature, mold in cold (soil) and yeast in warm (human body), examples: histoplasma, coccidioides, blastomyces

subcellular structures of fungi

1. capsule (in some)

2. cell wall

3. cell membrane

4. cytoplasm

5. nucleus

6. nuclear membrane

7. nucleolus

8. ER

9. mitochondria

10. vacuoles

capsule

made of polysaccharides and found in some fungi, antiphagocytic, Cryptococcus neoformans (encapsulated yeast), virulence factor that can cause chronic infections

cell wall

antigenic (can trigger immune response), multilayered (90% polysaccharides and 10% proteins and glycoproteins), provides shape and strength (protection from osmotic shock)

major polysaccharides of fungal cell wall

polymer = chitin, monomer = N-acetyl glucosamine

cellular membrane

bilayered, phospholipids and sterols (ergosterol and zymosterol), protects cytoplasm, controls solute concentrations, facilitates capsule and cell wall synthesis

types of spores

sexual, asexual, parasexual (genetic exchange)

types of sexual spores

1. zygospore

2. ascospore

3. basidiospore

4. oospore

what type of sexual spore is this

zygospore

zygospore

fusion of 2 haploid cells, diploid nucleus, thick-walled, can remain dormant for extended times, mating between + and - hyphae

what type of sexual spore is this

ascospore

ascospore

like a bag of spores, formed in an ascus (sac-like cell)

what type of sexual spore is this

basidiospore

basidiospore

spores formed at the ends of club-shaped cells called basidium

what type of sexual spore is this

oospore

oospore

thick-walled, egg-like

asexual spores

1. sporangiospores

2. arthrospores

3. blastospores

4. chlamydospores

5. macroconidium

6. microconidium

sporangiospores

endogenous, formed within a sporangium, the protoplasm cleaves around the nuclei

conidia

exogenous, mostly at the tip of supporting hyphae called conidiophores

blastic conidia

1st cell enlarges, 2nd septum forms

thallic conidia

1st septum forms, 2nd cell enlarges

what type of asexual spore is this

arthrospore

what type of asexual spore is this

blastospore

what type of asexual spore is this

chlamydospore

what type of asexual spore is this

macroconidia

what type of asexual spores is this

microconidia

what type of asexual spore is this

sporangiospore

arthrospores

formed by fragmenting specialized hyphal cells, rectangular

blastospores

budding in yeast, like Candida

chlamydospores

thick-walled, single celled, long-surviving, formed when vegetative cells contract

macroconidia

multi-celled, can have irregular shapes

microconidia

single-celled

mycosis

fungal infection

types of mycoses

1. superficial mycosis

2. cutaneous mycosis

3. subcutaneous mycosis

4. systemic (disseminated) mycosis

5. others

   1. dermatophytosis (skin, hair, nails)

   2. zygomycosis

   3. yeasts

   4. opportunistic mycosis (contaminants)

   5. pneumocystosis

superficial mycosis

outermost layers of epidermis called the stratum corneum

cutaneous mycosis

in the dermis layer (underneath epidermis)

subcutaneous mycosis

in deeper layers of connective tissue, under the skin, hypodermis layer

systemic (disseminated) mycosis

spread from the respiratory system to multiple organ systems

specimen from humans

sputum (phlegm), vaginal, urine, tissues, blood, exudates, pus, drainage, skin, hair, nails

direct specimen staining/examination

1. india ink preparations

2. gram stain procedure/calcofluor white

3. periodic acid-Schiff, hematoxylin and eosin, calcofluor white

4. gomori methenamine silver GMS stain

5. giemsa stain

india ink

distinguishing encapsulated yeast (Cryptococcus neoformans) in CSF, blue

what specimen are gram stain/calcofluor white used for

analyzing materials from mucous membranes, body fluids, urines, pink or purple

calcofluor white stain

observing fluorescent fungal elements in tissue, sputum, body fluids, skin scrapings, and corneal scrapings, example: C. albicans germ tubes

periodic acid-Schiff (PAS) stain

detects polysaccharides and therefore fungal walls, skin scrapings and tissue sections, pink color

gomori methenamine silver GMS

outlines fungi in deep black and the background green, on tissue sections, historically used with Pneumocystis jiroveci