Chapter 12

Single- or multi-cellular eucaryotic organisms that require organic compounds for nutrition. Saprophytic Primarily soil dwellers and plant pathogens; a few medically important parasites. Aerobes, facultative anaerobes, and a few anaerobes.

Morphology, Classified on basis of gross and macroscopic appearance.

Non-filamentous, unicellular fungi. Round or oval shape. Reproduce by fission or budding.

Thallus (body) consists of long filamentous cells (hyphae) that may or may not have septae (crosswalls). A growing, intertwining mass of hyphae is a mycelium.Reproduce by forming spores (sexual or asexual) or by fragmentation of hyphae.

Multiple forms. A few medically important fungi can grow as a mycelium(mold) or as yeast,depending on temperature and/or nutrition.

Fungal disease. Five major groups of infections.

Little or no reaction to infection. Essentially no pathology. No cellular response, remote from living tissue.

Superficial infection: Common inhabitants of skin, restricted to the stratum corneum.Causes discolored (depigmented) areas of skin on the chest, abdomen, back and arms (tinea versicolor).

Superficial infection: Causes tinea nigra. Brown to black scaly macules on palms and feet.

Cutaneous infections: Fungal infections with specific groups of fungi (Dermatophytes).

Colonize keratinized tissues (nails, hair, and stratum corneum). Non-invasive pathogens that produce an allergic, inflammatory response to metabolic products. Normally found in man, animals and soils.

Infections beneath the skin, but usually limited to the site of inoculation.Primary mode of entry is traumatic implantation of fungus through the skin. Little tendency to spread. Causative agents are usually normal soil inhabitants.

Caused by dematiaceous (pigmented) fungi, commonly found in rotting wood anddecaying forest litter. Phialophora spp., Fonsecaea spp., and others.

Sporothrix schenckii- causes a wide spectrum of chronic diseases. Most are nodules andulcers, limited to local area. Occasionally: spreads to bones and meninges, or (rarely) lungs. Grows on roses.

True pathogenic fungi. Route of infection almost always respiratory. Primary infection is asymptomatic in 90-95% of all cases.Strong immunity develops. Less than 5% of infections result in a respiratory disease, and a few cases result indisseminated disease, which is rare but very severe.-Disease can result any time the inoculum is of sufficient size.-The saprophytic (mycelial) form occurs in nature and is highly infectious.The yeast form grows in infected individuals and is not-infectious (unless directly inoculated).-Usually geographically restricted.

A soil inhabitant, endemic to Midwestern US. Infection is by inhalation of conidia. Appears in tissue as intracellular yeast (in macrophages).

Seen in North and Central America, and in Africa.Infective form is conidia. Seen in tissue as budding yeasts. Systemic spread may result in chronic granulomatous lesions of the skin and other organs. Found in bird guana.

Infection is by inhalation of sporesfrom soil. Appears in tissues as thick walled yeast cells with multiple buds. Survives in macrophages.

Soil fungus, endemic to southwestern US. Infectious form isarthrospores from fractured hyphae. Appears in tissues as spherules. Initial respiratory infection may be followed by flu-like disease, hypersensitivity reactions and pulmonary lesions ("valley fever" syndrome).

May be systemic, but these are not true pathogens.-Causative agents are of low inherent virulence. Patient's defenses must be abrogated before infection isestablished. Formerly very rare, but now much more common due to AIDS, use of antibiotics, and immunosuppressive drugs. Most opportunistic fungal infections can be attributed to a few species.-Some are present in small numbers as normal gut inhabitants and proliferate rapidly when the balance ofbacterial flora is upset. Some may gain entry to the body when a "barrier break" occurs.-tend to have a very wide distribution, but dimorphism is not seen.-Recovery does not give specific immunity. If defenses are weakened again, another outbreak can occur.

Oval budding yeasts. Normal flora of mucous membranes of respiratory,GI, and female GU tracts. May become dominant and cause disease locally. May become systemic in debilitated or immunosuppressed patients. Causes a wide variety of inflammations. Vaginal yeast infection, pseudohyphae.

Thick carbohydrate capsule. Occurs widely in nature, oftenassociated with pigeon feces. Highly opportunistic in humans. Infection via respiratory tract.

Agent of PneumoCystis Pneumonia (PCP). Most common infectious cause of death in AIDS patients. An extremely immunosuppressive yeast infection.

Single-celled eukaryotes. Mostly aerobic, water-dwelling heterotrophs.Some are normal microbiota; a few cause disease. Parasitic forms must get from host to host. Reproduction: asexual (fission, budding, schizogony) or sexual (conjugation, gametocyte formation).

Form a protective capsule (cyst); allows survival under adverse conditions.

is the vegetative (actively feeding and reproducing) form. Has to be in cyst form to infect. Has to be kind of wet to do it.

has undergone significant change recently (still not completed). Traditionally, the primary basis of " " of medically important species was means of locomotion. Recently, rRNA sequencing has provided a more accurate picture of evolutionary relationships, but has shuffled previously recognized groups.

Lack true mitochondria (mitosomes). Flagellates.

vaginitis, urethritis. Host to host transfer, no cyst form.

enteritis (inflammation of small intestines) from ingestion of cysts in contaminated water.

Obligate intracellular parasites that lack mitochondria and microtubules.

Diarrhea and keratoconjunctivitis(eye infection) in AIDS patients

Amoebas. Move by extension of pseudopodia

amoebic dysentery from ingestion of cysts

primarily corneal infections. Central nervous system in the immunocompromised.

May be highly invasive, but mature forms are non-motile, intracellular parasites.

malaria, transmitted by mosquitoes (the definitive host) to man (the intermediate host).

invade and reproduce in tissues after ingestion of oocysts. Associated with domestic cats; very dangerous to pregnant women

potentially lethal respiratory and gall bladder infections in the immunosuppressed.Oral transmission (feces or contaminated water).

ciliates

Ingestion of cysts leads to dysentery. Organism is occasionally invasive.

hemoflagellate sub-group

African sleeping sickness (Trypanosomiasis).Transmitted by tsetse fly.

Chagas disease, (American trypanosomiasis). Transmitted by kissing bug.Naegleria fowleri (dinoflagellate and amoeboid forms)