Fungi(Chapter 28)

“a group of diverse and widespread unicellular and multicellular organisms,

lacking chlorophyll, usually bearing spores and often filamentous”

Fungal Infections

• last 10 years incidence of serious fungal infections has been increasing

• nosocomial in nature and impacting the immunocompromised

• need organic compounds and carbon: energy

• aerobic or facultatively anaerobic

Categories of Fungi

• Page 410• 1) yeasts

• 2) molds

• 3) dimorphic fungi

Yeasts• spherical or oval Figure 28-1

• “budding”: parent cell forms a protuberance• parent cell’s nucleus divides and one nucleus migrates

into the “bud”

• 1 yeast cell can produce up to 24 daughter cells by “budding”

• “buds” may form a short chain of cells

Molds

• thallus (body)

• hyphae (filaments)

• septa (cross-walls)

• septate hyphae: hyphae that contain septa

Dimorphic Fungi

• 2 forms of growth in pathogenic species– 1) mold– 2) yeast

• Mold: hyphae (multicellular)

• Yeast: buds (unicellular)

Dermatomycosis• Page 411

• caused by dermatophytes• infect the epidermis, hair, and nails• secrete enzyme: keratinase (degrades keratin,

protein found in hair, skin and nails)• direct contact, infected hairs and epidermal cells

(barber shop clippings, shower room floors)• 3 genera: Trichophyton, Microsporum,

Epidermophyton

Dermatomycosis (cont’d)

• 3 genera:• Trichophyton: infect hair, skin or nails• Microsporum: infects hair or skin• Epidermophyton: infects skin and nails• Examples of infection: tinea capitis tinea cruris tinea pedis• Color Plates: 67 and 68

Coccidioidomycosis

• respiratory disease caused by the fungus Coccidioides immitis (extremely virulent)

• Spores found in dry, alkaline soils in the American Southwest, Mexico and S. America

• wind carries the spores and transmits the infection (passing through endemic areas can lead to infection)

• AKA: Posada-Wernicke disease, cocciodioidal granuloma, Valley/California/San Joaquin fever, desert rheumatism, valley bumps,

Diagnosis

• spherules (spores) in tissues or fluids

• cultures of tissues or lesions

• laboratory workers: infectious aerosols

• increasing in California and Arizona– elderly population, droughts, HIV/AIDS

Histoplasmosis

• fungal infection of the respiratory system caused by Histoplasma capsulatum

• AKA reticuloendothelial cytomycosis, cave disease, spelunker’s disease, Darling’s disease

• highest incidence: Ohio, Missouri and Missippi Delta• found in bird droppings and bats• airborne spores enter ventilation systems• infected host asymptomatic, can become systemic

and fatal (COPD)

Candidiasis

• bacterial microbiota (genitourinary tract and mouth) usually suppress infection

• not affected by antibacterial drugs• changes in normal mucosal pH encourage

growth (antibiotic therapy)• Readings question #1: What microorganisms

cause candidiasis? How may this infection appear in infants? What is it called?

• Color Plate 69

Cryptococcosis

• Page 413 AKA fungal meningitis, cryptococcal meningitis due to Cryptococcus neoformans

• spherical cells that reproduce by “budding”• have thick polysaccharide capsules• found in soil, pigeon roosts and nests• transmitted by inhalation of dried droppings• Figure 28 – 2• usually subclinical unless “high risk” • if systemic: brain and meninges

Brain Tissue with Cavities

Aspergillosis

• Readings question #2: What is the causative fungus? Where is it found? How is it spread? What are the symptoms for the disease?

Pneumocystis Pneumonia(PCP)

• Page 415• caused by Pneumocystic carinii (P. jiroveci) found

in healthy human lungs• high infection rate in general population but “high

risk” have few or no symptoms• reside in lining of the alveoli• diagnosis: sputum samples (cysts from bronchoalveolar lavage)

Readings Question #3

• How is the disease PCP spread? What are its symptoms? Is it potentially fatal? (If yes, how does death occur?)