Microbiology Midterm Flashcards
1
Q
Fungi
A
- They are saprophytes (derive nourishment from dead material) or sometimes parasitic
- About 100 of the 250,000 known species are pathogens
- Slow growing eukaryotes (similar to us)
- Can produce a wide variety of toxins
- Heterotrophs (require a preformed carbon source for growth)
- Secrete degradative enzymes and then absorb released nutrients
- Love dead and decaying matter, however will colonize in humans
2
Q
Serious Fungal Infections in Healthy People are Very Rare, BUT…
A
- The population is aging
- There are more immunosuppressed people due to HIV, transplants, and chemo
- The development of antifungals has not kept up with need for treatment
3
Q
Fungi: Groups
A
- True Pathogens
a) Cutaneous infective agents
b) Sub-cutaneous infective agents
c) Systemic infective agents - Opportunistic Pathogens
4
Q
Fungi: Cellular Components
A
- Cell wall contains chitin, a polymer of N-acetylglucosamine (vs. peptidoglycan in bacteria)
- Cell membrane contains ergosterol (vs. cholesterol in mammals)
- Principle method of reproduction and spread is sporulation
5
Q
Fungi: Filamentous Molds
A
Cottony, fluffy colonies that grow up
Composed of…
-Mycelium: A vegetative body made of many threads, looks like cotton ball
-Arial hyphae: Tubes that grow up from the agar
-Vegetative hyphae: Tubes that grow into the agar
+Can be septate or non septet hyphae, depending on presence of internal dividers
6
Q
Fungi Reproduction: Asexual Sporulation
A
- Conidia (asexual spores) are formed by specialized hyphae called conidiophores via mitosis
- Disperse on air currents
7
Q
Fungi Reproduction: Sexual Sporulation
A
- Haploid nuclei from two compatible strains of the same species fuse to form a diploid
- Diploid undergoes meiosis to form ascospores
- Much rarer than asexual
- Spores tend to be distinctive to individual species and can be used to speciate samples
8
Q
Fungi: Unicellular Yeasts
A
- Creamy, pasty colonies
- More likely to cause damage in the body
- Exist in colonies of unconnected, single cells
- Commonly spherical
- Cells are 10X bacteria size
- Reproduce by budding
9
Q
Fungi: Cutaneous Mycoses
A
- Usually caused by the dermatophytes (3 different species - Trichophyton, Epidermophyton, Microsporun)
- Can be anthropophilic (prefer human skin), zoophilic (animal skin), or geophilic (soil)
- Dermatophytes use keratin as a source of nutrition
- They infect skin, hair and nails but do not infect the deeper, non-keratin containing tissues
- Produce itching, scaling skin patches that can become inflamed or weeping
- More than one fungi can infect a body part
- Remove infected skin and treat with topicals
10
Q
Athlete’s Foot
A
Tinea pedis
- Cutaneous mycoses
- Caused by Trichophyton rub, T. mentagrophytes, Epidermophyton floccosum
- Starts between the toes, spread to toe nails, which become yellow and brittle
- If skin is broken, bacterial infection can result
- Common in pools, gyms, public showers
11
Q
Ringworm
A
Tinea corporis
- Cutaneous mycoses
- Caused by Epidermophyton floccosum, several species of Trichophyton and Microsporum
- Lesions appear as annual rings with a scaly centre, frequently on non-hairy areas of the chest
- Outside of ring is where fungi are growing and producing inflammation
12
Q
Scalp Ringworm
A
Tinea wapitis
- Cutaneous mycoses
- Most commonly caused by Trichophyton and Microsporum
- Infected areas can range from small scaly patches to entire scalp
- Can result in hair loss
- If Microsporum infects hair shaft, a Woods lamp (long wave UV) will make hair glow green
13
Q
Jock Itch
A
Tinea cruris
- Cutaneous mycoses
- Caused by E. floccosum and T. rubrum
- Similar to ringworm, but occurs in moist groin area
- Can spread to thighs and genitalia
- Common in young adult males
14
Q
Onychomysosis
A
Tinea unguium
- Cutaneous mycoses
- Usually caused by T. rubrum
- Toenails become thick, discolored and brittle
- Need to treat for months until the uninfected portion of the nail grows out
- Common in older people
15
Q
Fungi: Subcutaneous Mycoses
A
- Infections of the dermis, subcutaneous tissues and bone
- Results from puncture wounds
- No person to person transmission
- Common in those who have close contact with soil and vegetation, but do not wear gloves
