Fungi and Parasites

Mycology

is the study of fungi

Fungi

are eukaryotic, nonmotile, non-photosynthetic organisms.

fungi

Most ______ are obligate or facultative aerobes.

nucleus

Like all eukaryotes, each fungal cell has at least one ___________ with a nuclear membrane, endoplasmic reticulum, mitochondria, and secretory apparatus.

chitin, mannan, and other polysaccharides

Fungi cells possess a rigid cell wall that contains...

Chemotrophs

obtain energy by the oxidation of electron donors in their environments

Chemotrophic

Fungi are ________________

- They secrete enzymes that degrade a wide variety of organic substrates into soluble nutrients

50

Approximately 80,000 species of fungi have been described, less than ______ are responsible for most of the fungal infections of humans and other animals.

Saprophytes

essential in breaking down and recycling organic (dead) matter

fungi

Most species of _______ are beneficial to humankind.

1. They reside in nature and are essential in breaking down and recycling organic matter (saprophytes).

2. are contributing to the production of some food including cheese, bread, and beer.

3. Some fungi are providing useful bioactive secondary metabolites such as antibiotics (eg, penicillin) and immunosuppressive drugs (eg, cyclosporine).

phytopathogens

fungi have a great economic impact as ____________________; the agricultural industry sustains huge crop losses every year as a result of fungal diseases of rice, corn, grains, and other plants.

Taxonomic Classification (Fungi)

Phylum Thallophyta (a division of the plant kingdom), which includes fungi, algae, and lichens

Thallophyta

The taxonomic classification of fungi is Phylum...

Fungi

has four classes:

Zygomycetes, Ascomycetes, Basidiomycetes, Deuteromycetes

Yeasts

single celled fungi

Molds

mycelial (filamentous) fungi

Dimorphic Fungi

exhibit a yeast phase (Y) and a mold phase (M). The fungi can switch from growth as a mycelial form at external cooler temperatures to growth as yeast at human body temperatures → called the Y-M shift

mycoses (mycotic diseases)

The diseases caused by fungi are called...

Fungal Infections

are subdivided into

I. Superficial mycosis

II. Cutaneous mycosis

III. Subcutaneous mycosis

III. Systemic mycosis

IV. Opportunistic mycosis

Superficial Mycoses

is limited to the outermost layers of the skin (the dead layers, stratum corneum), and hair shafts:

1. Pityriasis versicolor

2. Tinea nigra

3. Black Piedra

4. White Piedra

Pityriasis versicolor

superficial mycoses - pigmented lesion on the trunk of the body

Tinea Nigra

superficial mycoses - gray to black macular lesion on palms

Black Piedra

superficial mycoses - dark gritty nodules on hair

White Piedra

superficial mycoses - soft whitish granules along hair shaft

Cutaneous mycoses

Infections that extend deeper into the epidermis, as well as hair and nail and are caused by Dermatophytes.

→ Three genera of dermatophytes fungi cause tineas infections

1. Trichophyton - skin, hair and nail infections.

2. Microsporum - skin and hair.

3. Epidermophyton - skin and nails.

Trichophyton

dermatophyte that causes tineas infections (cutaneous mycoses) of the skin, hair and nails

Microsporum

dermatophyte that causes tineas infections (cutaneous mycoses) of the skin and hair

Epidermophyton

dermatophyte that causes tineas infections (cutaneous mycoses) of the skin and nails

Subcutaneous Mycoses

These involve the deeper layers of the skin (the dermis, subcutaneous tissue, muscle & fascia and even bone). Subcutaneous infections include:

1. Maduromycosis (Mycetoma)

2. Chromoblastomycosis

3. Sporotrichosis

Maduromycosis (Mycetoma)

subcutaneous mycoses - chronic granulomatous infection of subcutaneous tissue usually affects foot.

Chromoblastomycosis

subcutaneous mycoses - a chronic granulomatous infection caused by several different dematiaceous fungi (brown pigment-producing), resulting in the formation of slow-growing, warty plaques, cauliflower-like lesions.

Sporotrichosis

subcutaneous mycoses - nodular ulcerating disease of skin, most common subcutaneous mycotic disease, the disease, is an occupational hazard for florists, gardeners, and forestry workers.

Systemic Mycoses

are fungal infections affecting internal organs.

- Most systemic mycoses are acquired by inhalation of spores where the infection develops initially in the lungs; later, the skin and other organs may be involved.

- The spores of fungi, normally live in the soil or rotting vegetation.

- The fungi that cause systemic mycoses are dimorphic

dimorphic

The fungi that cause systemic mycoses are...

Coccidioidomycosis

systemic mycoses - spread in North and south America, caused by Coccidioides immitis.

Coccidioides immitis.

Coccidioidomycosis is a systemic mycoses - spread in North and south America, caused by...

Histoplasmosis

systemic mycoses - a disease of the lungs caused by Histoplasma capsulatum. It is common among poultry farmers, spelunkers, and bat guano miners

Histoplasma capsulatum

Histoplasmosis - systemic mycoses - a disease of the lungs caused by ______________________. It is common among poultry farmers, spelunkers, and bat guano miners

Blastomycosis

systemic mycoses - caused by Blastomyces dermatitidis

- The initial infection begins in the lungs.

- It often spreads to the skin, where cutaneous ulcers and abscess formation occur

Blastomyces dermatitidis

Blastomycosis - systemic mycoses - caused by...

Paracoccidioidomycosis

systemic mycoses - caused by Paracoccidioides

- usually affects the lungs and skin

- it most often affects men who work outdoors in rural areas

Paracoccidioides

Paracoccidioidomycosis - systemic mycoses - caused by...

Opportunistic Mycoses

Other systemic mycoses only infect those who are already sick or with an immunodeficiency disorders. Repeated infection may occur.

- Risks for systemic mycoses include:

1. Serious illness and debility

2. Cancer or leukemia

3. Diabetes mellitus

4. Transplant

5. Massive doses of antibiotics

6. Parenteral nutrition

7. Drug addiction

8. Infection with human immunodeficiency virus (HIV)

Candidiasis

- Caused by Candida albicans, a classic opportunistic pathogen

- Part of the endogenous microbiota (Skin, Gut, Mucosal surfaces) → Most infections are due to a person's own flora

- Oral candidiasis

- Angular stomatitis (with denture wearers)

- Candida intertrigo: infection with body intertrigo (moist folds)

- Genital candidiasis: commonly presents as a sore itchy vulvovaginitis

Candida albicans

Candidiasis is caused by __________________, a classic opportunistic pathogen

Aspergillosis

infection results only when healthy immune functions deteriorate.

- The major portal of entry for Aspergillus spp. is the respiratory tract (Inhalation of spores)

Aspergillus fumigatus

is the species commonly involved in pulmonary aspergillosis

- Pulmonary infection may result in the development of an aspergilloma → fungal colonies form within the lungs and develop fungus balls (consisting of a tangled mass of hyphae)

Allergic aspergillosis

individuals develop an immediate allergic response and suffer asthma attacks when exposed to fungal antigens.

- It also causes superficial infection

Invasive aspergillosis

In some cases, invasive disease of immunosuppressed patients results when pulmonary infection disseminates to the brain, kidney, liver, bone, or skin.

- ___________________ has a mortality rate of 50 to 100%

less

Treatment of fungal infection is _______ successful than that of bacterial infections

Antifungals

Many drugs that inhibit or kill fungi are quite toxic to human cells.

▪ Many fungi have a detoxification system that modifies many antifungals, probably by hydroxylation.

- So the antifungal drug becomes more fungistatic (most of the antifungals) → Repeating application may maintain high levels of the unmodified drug.

fungistatic

most antifungals are...

parasite

A living organism that acquires some of its basic nutritional requirements through its intimate contact with another living organism.

→ may be simple unicellular protozoa or complex multicellular metazoan

protozoa

unicellular organisms

metazoa

multicellular organisms (i.e. helminths) and arthropods

Endoparasite

a parasite that lives within another living organism

- e.g. the causative agent of malaria (Plasmodium), or Giardiasis (Giardia lamblia)

Ectoparasite

a parasite that lives on the external surface of another living organism

- e.g. lice, ticks

Host

the organism in, or on, which the parasite lives and causes harm

defensive host

the organism in which the adult or sexually mature stage of the parasite lives

intermediate host

the organism in which the parasite lives during a period of its development only.

vector

a living carrier (e.g., an arthropod) that transports a pathogenic organism from an infected to a non-infected host.

- A typical example is the female Anopheles mosquito that transmits malaria.

Malaria

is one of the widespread protozoal disease caused by the genus Plasmodium.

- Human malaria is caused by five species of Plasmodium. In descending order of incidence, they include: P. falciparum, P. vivax, P. malariae, P. ovale, and P. knowlesi.

- The vector of plasmodium is the female Anopheles mosquito

Plasmodium

malaria is one of the widespread protozoal disease caused by the genus...

female Anopheles mosquito

The vector of plasmodium (causative agent of malaria) is the...

Amebiasis (amebic dysentery)

is caused by the amoeba Entamoeba histolytica

- Infection occurs by ingestion of fecally contaminated water, food, or hands.

- E. histolytica Infect the gastrointestinal tract system also may invade and produce lesions in other tissues, especially the liver, to cause hepatic amebiasis.

Entamoeba histolytica

Amebiasis (amebic dysentery) is caused by the amoeba...

Leishmaniasis

are a group of human diseases caused by over 20 species of Leishmania parasites.

- The most common forms are cutaneous, mucocutaneous, and visceral (affecting liver, spleen, and blood).

- are transmitted from animals (rodents and canines) to humans, or between humans, by female sand flies

Leishmania parasites

Leishmaniasis are a group of human diseases caused by over 20 species of...

female sand flies

what is the main vector of Leishmania?