Download Fungi

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)
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•
•
•
•
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?)