PHMP (MIDTERM): P1 Mycology

Mycology

branch of biology that deals with the study of fungi,

including genetic and biochemical properties, taxonomy as well as pathogenesis and toxicity

Fungi

Eukaryotic microorganisms that occur ubiquitously in nature in the domain Eucarya

50,000

200

kingdom fungi (Mycota) has over ___ different species but only ___ have been identified as human pathogens.

Study table pg.1

Chitin

fungal cell walls

Chitin

a polysaccharide composed of long chains of N-acetylglucosmine and plenty of polysaccharides such as

β- glucan

β- glucan

a long polymer of D- glucose

Medically important ( site of echinocandin action)

echinocandin

B-glucan synthesis inhibitor

Ergosterol

- Fungal Cell membrane

- alternative in human cholesterol

- Site of action of Ampothericin B and Azoles

Amphotericin B

Most powerful antifungal given parenteral

Yeast

mold

Two types of Fungi

Yeast

single cell that reproduce through budding

Molds

Grow as long filaments (hyphae) and form a mat (mycelium)

Hyphae

long, threadlike filaments that make up the mycelium (body) of a fungus.

Septate hyphae

hyphae for Transverse walls

nonseptate hyphae

No transverse wall

Dermatophytes

Morphology: Classifications:

causes infection of the keratinized (skin) tissues

Yeast

Morphology: Classifications:

single cells

Molds:

Morphology: Classifications:

grow in filamentous structures

Dimorphic fungi

Morphology: Classifications:

They exist as molds in the environment at ambient temperature and as yeasts (or other structures) in human tissues at body temperature

Can be molds or yeast

Hypha

Morphology:

basic element of filamentous

fungi with a branched, tubular structure,

2-10lm in width.

Mycelium

Morphology:

web or matlike structure of hyphae

Substrate mycelia

(specialized for nutrition) penetrate into the nutrient substrate.

Aerial mycelia

(for asexual propagation) develop above the nutrient medium

Fungal thallus

Morphology:

entirety of the mycelia and is also

called the fungal body or colony

Yeast

Morphology:

basic element of the unicellular fungi.

-round to oval and 3- 10 micrometer in diameter.

- Several elongated yeast cells chained together and resembling true hyphae are called pseudohyphae

Dimorphism

Morphology:

some fungal species can develop either the yeast or the mycelium form depending on the environmental

conditions,

a property called dimorphism.

Dimorphic pathogenic fungi

take the form of yeast cells in the parasitic stage and appear as mycelia in the saprophytic stage

carbon heterotrophs

Obligate aerobes

Metabolism:

All fungi are ___

- Dependent on exogenous nutrient substrates as sources of organic carbon, and with a few exceptions,

- fungi are obligate ___.

- None are obligate anaerobes

• Thermophilic

• Psychrophilic

• Acidophilic

• Halophilic

Known Metabolic Types: (4)

Sexual reproduction

• They reproduce sexually by mating and forming sexual spores

Zygospores

Sexual reproduction:

single large spore with thick walls

Ascospores

Sexual reproduction:

Formed in a sac called ascus

Basidiospores

Sexual reproduction:

Formed externally on the tip of the pedestal called basidium

Asexual reproduction

Some Important Conidia:

•Formation of conidia (__spores) from the sides or the ends of specialized structures

Arthrospore

Asexual reproduction:

arises by fragmentation of the ends of the hyphae( mode of transmission of Coccidiodes immitis)

Chlamydospore

Asexual reproduction:

rounded, thick-walled and quite resistant.

Blastospores

Candida albicans

pseudohyphae

Asexual reproduction:

- formed by budding process of yeast

• Some yeast ( ___, can form

multiple buds that do not detach, thus producing sausage-like chains called ___

Sporangiospores

Asexual reproduction:

formed within a sac (sporangium) on a stalk by molds such as Rhizopus and Mucor

•Superficial mycoses

•Cutaneous mycoses

Subcutaneous mycoses

•Deep Mycoses

- Systemic mycoses:

- Opportunistic mycoses:

Important Fungal Diseases

Medical Mycoses according to site of infection: (4) + 2

Systemic mycoses

• Fungi that are able to cause systemic infection

• Primarily involve the respiratory system

Opportunistic mycoses

• Systemic infection caused by normal flora that become opportunistic in immunocompromised patients

supericial Mycoses

These are limited to the stratum corneum and essentially elicit no inflammation.

Pityriasis versicolor

1.) a common superficial mycosis,

characterized by hypopigmentation or hyperpigmentation of skin of the neck, shoulders, chest, and back.

Malassezia furfur (CA of Anan)

Malassezia globosa

Malassezia restricta,

Pityriasis versicolor is due to (3)

,which involves only the superficial keratin layer.

Black piedra

Piedraia hortae

2.) Superficial Mycoses:

superficial mycosis due to __

which is manifested by a SMALL FIRM BLACK NODULE involving the HAIR shaft.

White piedra

Trichosporon beigelii

3) Superficial Mycoses:

due to ___

is characterized by a larger, softer and yellowish nodules on hair

Tinea nigra

Hortaea werneckii

4) Superficial Mycoses:

most typically presents as a brown to black silver nitrate-like stain on the palm of the hand or sole of the foot

and caused by ___

Dermatophytoses:

1.) Cutaneous Mycoses:

caused by fungi (dermatophytes) that infect only superficial keratinized structures (skin, hair, and nails), not deeper tissues.

Microsporum

Trichophyton

Epidermophyton

Dermatophytoses 3 important genera

Microsporum

Infects hair and skin but not the nails

Trichophyton

Infects hair, skin and nails

Epidermophyton

Infects skin and nails but not the hair

Dermatomycoses:

2) Cutaneous Mycoses:

cutaneous infections due to other fungi, the most common of

which are Candida spp

Tinea pedis (athlete's foot)

1. Dermatophytes:

: affects the feet

Tinea unguium (Onchomycosis)

2. Dermatophytes:

: affects the fingernails and

toenails

Tinea corporis (ringworm)

3. Dermatophytes:

affects the arms limbs and trunk

Tinea cruris (jock itch)

4. Dermatophytes:

: affects the groin area

Tinea manuum

5. Dermatophytes:

affects the hand and palm area worse than tinea pedis

Tinea capitis

6. Dermatophytes:

: affects the scalp

Tinea barbae/Barber's Itch

7. Dermatophytes:

affects the facial hair

Tinea faciei (Face fungus)

8. Dermatophytes:

: affects the face

Subcutaneous Mycoses

☐These include range of different infections characterized by infection of the SUBCUTANEOUS TISSUE usually at the point of traumatic inoculation

☐An inflammatory response

develops in the SUBCUTANEOUS TISSUES frequently with EXTENSION

into the EPIDERMIS.

☐Chromoblastomycosis

☐Mycetoma

☐Sporothricosis

Subcutaneous Mycoses

3 general types

Chromoblastomycosis

1.) Subcutaneous Mycoses:

- Subcutaneous mycosis

characterized by VERRUCOID LEDIONS of the skin (usually of the lower extremities);

- Histological examination

reveals MURIFORM CELLS (with perpendicular septations) or so-called

"copper pennies" that are

characteristic of this infection.

Chromoblastomycosis

2.) Subcutaneous Mycoses:

- Generally limited to the

subcutaneous tissue with no involvement of bone, tendon, or

muscle.

1. Fonsecaea pedrosoi

☐ Pedroso's disease

2. Fonsecaea compacta

☐ Fonseca's disease

3. Cladophialophora carrionii,

☐ Cladosporiosis

4. Rhinocladeiella aquaspersa

5. Phialophora verrucosa.

(5) most common causes of

chromoblastomycosis

Mycetoma (Madura foot)

3.) Subcutaneous Mycoses:

- suppurative and granulomatous subcutaneous mycosis, which is destructive of contiguous bone, tendon, and skeletal muscle.

- characterized by PRESENCE OF DRAINING SINUS TRACTS from which small but grossly visible pigmented

grains or granules are

extruded.

eumycotic and actinomycotic mycetoma

causes of mycetoma

are more diverse but can be

classified as ____ and ___

☐ Eumycotic mycetoma

Pseudallescheria boydii

☐Actinomycotic mycetoma

Nocardia brasiliensis.

2 most common agent of MYCETOMA

Dematiaceous (melanized) Fungi

dematiaceous hyphal

Fungi causing mycetoma

• Pigmented brown to black.

• melanin pigment is deposited in the cell walls of these organisms.

• These fungi may produce range of infections from superficial to subcutaneous to deep (visceral) infection characterized by the presence of ____ and/or yeast-like cells in tissue.

phaeohyphomycosis

Such deep infections due to dematiaceous fungi are termed ___.

Sporotrichosis

3) Subcutaneous Mycoses:

• infection is due to Sporothrix schenckii and involves the subcutaneous tissue at the point of traumatic inoculation.

• The infection usually spreads along cutaneous lymphatic channels of the extremity involved.

Systemic Mycoses

respiratory tract

1.) Deep Mycoses:

- primary pathogenic fungi are able to establish infection in a normal host

• The primary deep pathogens usually gain access to the host via ___

Coccidioides immitis

Histoplasma capsulatum

Blastomyces dermatitidis

Paracoccidioides brasiliensis.

primary systemic fungal pathogens (4)

Common to immunocompromised px

Coccidioidomycosis

1.) Deep Primary Mycoses:

Known as the "Valley Fever"

- The arthrococonidia of Coccidioides immitis are inhaled and convert in the lung to spherules.

- Most cases of are clinically occult or mild infections in patients who inhale infective arthroconidia.

- Some patients have progressive pulmonary infection and also may suffer dissemination to the brain, bone, and other sites.

Coccidioides meningitis

is a life-threatening infection requiring lifelong treatment.

Histoplasmosis

2.) Deep Primary Mycoses:

- primary pulmonary infection resulting from inhalation of conidia of Histoplasma capsulatum which convert in vivo into the blastoconidial (budding yeast) form

- Dissemination to hilar and mediastinal lymph nodes, spleen, liver, bone marrow, and brain may be life-threatening in infants and other immunocompromised patients.

- Common in AIDS

intracellular growth

Histoplasmosis (like tuberculosis) is characterized by __ of the pathogen in macrophages and a granulomatous reaction in tissue.

fibrosing mediastinitis

Histoplasma capsulatum

Histoplasmosis also may be associated with a chronic inflammatory process known as ___

where scar tissue (formed in response to ___) encroaches on vital structures in the mediastinum (mid chest area)

Blastomycosis (North American Blastomycosis)

CA: Blastomyces dermatitidis

3.) Deep Primary Mycoses:

- Similar to histoplasmosis, is a primary pulmonary infection resulting from inhalation of conidia from the mycelial phase of Blastomyces dermatitidis which convert in vivo to the parasitic yeast phase.

- In the blastoconidial phase also causes a primary pulmonary infection.

- This may cause chronic pneumonia

- organism elicits a granulomatous reaction often associated with a marked fibrotic reaction.

Disseminated Blastomycosis

spread of the fungi to the skin, bones and prostate in male

Paracoccidioides brasiliensis

4) Deep Primary Mycoses: Paracoccidiodes

AKA South American blastomycosis.

- causes paracoccidioidomycosis

- dimorphic fungus that exists as a mold in soil and as a yeast in tissue. The yeast is thick-walled with multiple buds, in contrast to B. dermatitidis, has a single bud

- This fungus grows in the soil and is endemic in rural Latin America.

Disease occurs only in that region

Paracoccidioides

yeasts with multiple buds resembling a "ship captain's wheel."

Stain: Methenamine silver stain

Deep Opportunistic Mycoses

Opportunistic fungi causing deep mycosis invade via the respiratory tract, alimentary tract, or intravascular devices.

Opportunistic pathogens

require a compromised host in order to establish infection (e.g., cancer, organ transplantation, surgery, and AIDS).

1. Cryptococcus neoformans

2. Candida spp.

3. Aspergillus spp.

4. Penicillium marneffei

5. the Zygomycetes

6. Trichosporon beigelii

7. Fusarium oxysporum

opportunistic fungal pathogens (7)

Candidiasis

1.) Deep Opportunistic Mycoses:

(due to C albicans and other Candida spp.) is the most common opportunistic fungal infection.

Candida albicans

is the most common cause of candidiasis.

Superficial candidiasis

may involve the epidermal and mucosal surfaces, including those of the oral cavity, pharynx, esophagus, intestines, urinary bladder, and vagina

Deep (or visceral) candidiasis.

The alimentary tract and intravascular catheters are the major portals of entry

The principal risk factors predisposing to deeply invasive __ are protracted courses of broad spectrum antibiotics, cytotoxic chemotherapy, corticosteroids, and vascular catheters.

kidneys,

liver,

spleen,

brain,

eyes,

heart,

and other tissues

major organ sites involved in deep or visceral candidiasis (6)

Interdigital candidiasis

Cutaneous candidiasis

Nappy rash

Diaper candidiasis

- infection between the digits of the hands and feet, either scaling or maceration evident on a red base

- Singit

- in infant that spreads in the mouth

- that resembles tinea

Aspergillosis

Aspergillus fumigatus

respiratory tract

2.) Deep Opportunistic Mycoses:

Invasive __ most frequently involves the lungs and paranasal sinuses.

•The fungus, ___may disseminate from the lungs to involve the brain, kidneys, liver, heart, and bones.

main portal of entry ___

Rhizopus,

Rhizomucor,

Absidia,

Mucor species

3.) Deep Opportunistic Mycoses:

Zygomycosis due to (3), or other members of the class of Zygomycetes, also causes invasive Sinopulmonary infections.

Mucormycosis

rhinocerebral syndrome

An especially life-threatening form of zygomycosis (also known as ____), is known as the ____, which occurs in diabetics with ketoacidosis, this disease is highly lethal

Cryptococcosis

Cryptococcus neotormans

4.) Deep Opportunistic Mycoses:

- an encapsulated yeast that is most typically an opportunistic fungal infection that most frequently causes pneumonia and/or meningitis.

- Defective cellular immunity, especially that associated with the acquired Immune deficiency syndrome, is the most common risk factor for Developing cryptococcosis.

- CA ___

Phaeohyphomycosis

5.) Deep Opportunistic Mycoses:

- an infection by brown to black pigmented fungi of the cutaneous, superficial, and deep tissues, especially brain.

- These infections are uncommon, life-threatening, and occur in various

immunocompromised states.

Hyalohyphomycosis

6.) Deep Opportunistic Mycoses:

opportunistic fungal infection caused by any of a variety of normally saprophytic fungi with HYALINE HYPHAL elements.

hyaline hyphal elements

• fungal agent with septate hyphae and nonpigmented (hyaline)

• Traditionally, the disseminated and corneal forms of hyalohyphomycosis have been most commonly identified