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Definition
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Term
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Definition
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Term
| Three ways fungi may be beneficial to humans: |
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Definition
i. Involved in the decay of dead plants and animals
ii. Involved in the manufacturing of various industrial and food products
iii. Involved in the production of many common antibiotics
iv. May be eaten as food |
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Term
| Three ways they may be harmful: |
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Definition
i. Damage wood and fabrics
ii. Spoil foods
iii. Cause a variety of plant and animal diseases including human infection |
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Term
| Describe the typical appearance of a yeast cell and its usual mode of reproduction. |
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Definition
- Oval or spherical fungi
- Reproduce asexually by budding
o A bud forms on the outer surface of a parent cell, the nucleus divides with one nucleus entering the forming bud, and cell wall material is laid down between the parent cell and the bud. |
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Term
| Describe yeasts in terms of their oxygen requirements |
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Definition
| - Yeast are facultative anaerobes – can obtain energy from both aerobic respiration and anaerobic fermentation |
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Term
| State two ways the yeast Saccharomyces is beneficial to humans |
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Definition
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Term
| Name three yeasts that commonly infect humans. |
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Definition
a. Candida
b. Cryptococcus neoformans
c. Pneumocystis jiroveci |
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Term
| Name four common forms of candidiasis. |
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Definition
a. Candida albicans
b. Candida glabrata
c. Candida parapsilosis |
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Term
| Describe two conditions that may enable Candida to cause severe opportunistic systemic infections. |
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Definition
a. Antibiotic therapy
b. Cytotoxxic and immunosuppressive drugs
c. Immunesuppressive diseases such as diabetes, leukemia , and AIDS |
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Term
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Definition
| filament like structure produced by budding yeast that do not break off |
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Term
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Definition
| long branching filament lacking complete septa |
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Term
| describe blastoconidia (blastospores) |
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Definition
| asexual spores , develop in clusters along the hypae often at the points of branching. |
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Term
| describe chlamydoconidia (chlamydospores) |
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Definition
| thick walled survival spores |
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Term
| state the usefulness of Saboraud Dextrose agar |
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Definition
| inhibits bacterial growth and promotes fungal growth |
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Term
| state the usefulness of Mycosel agar |
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Definition
| contains chloramphenicol which inhibits bacteria and cycloheximide which inhibits most saprophytic fungi. Mycosel agar is selective for pathogenic fungi. |
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Term
| state the usefulness of Rice Extract agar |
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Definition
| has polysorbate 80 which stimulates the formation of hyphae , blastoconidia and chlamydoconidia which are structures unique to Candida albicans |
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Term
| State how Cryptococcus neoformans is transmitted to humans, where in the body it normally infects, and possible complications. |
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Definition
- Inhalation of the yeast in dried bird feces
- It normally infects the lungs
- In an immunosuppressed person it may spread through the blood to the meninges and other body area often causing cryptococcal meningoencephalitis |
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Term
| 12. State the primary method of identifying Cryptococcus neoformans when causing cryptococcal meningoencephalitis. |
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Definition
| - Can be identified by preparing an india ink or nigrosin negative stain of suspected sputum or cerebral spinal fluid in which the encapsulated, budding, oval yeast cells may be seen. |
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Term
| 13. State what disease is caused by Pneumocystis jiroveci and indicate several predisposing conditions a person is normally seen to have before they contract the disease. |
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Definition
- Causes Pneumocystis pneumonia (PCP)
- AIDS, late stage malignancies , leukemias |
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Term
| 14. Name an infection caused by Malassezia globosa. |
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Definition
| - Superficial skin infection called tinea vesicolor |
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Term
| 15. Describe the appearance of Saccharomyces cerevisiae and Candida albicans on Saboraud Dextrose agar and on Mycosel agar. |
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Definition
- Candida albicans has a creamy white growth on both agars
- Saccharomyces cerevisiae has a creamy white growth only on SDA agar and does not grow on Mycosel agar |
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Term
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Definition
| a branching, tubular structure from 2- 10 micrometers in diameter and is usually divided into eukaryotic cell like units by crosswalls called septa |
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Term
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Definition
| the total mass of a hyphae |
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Term
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Definition
| the portion that produces asexual reproductive spores |
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Term
| define vegetative mycelium |
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Definition
| The portion of the mycelium that anchors the mold and absorbs nutrients |
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Term
| 2. Describe the principle way molds reproduce asexually. |
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Definition
- Molds reproduce primarily by means of asexual reproductive spores such as conidiospores , sporangiospores and arthrospores
- These spores are disseminated by air, water. Animals or objects and ipon landing on a suitable environment germinate and produce her hyphae |
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Term
| 3. State the main criteria used in identifying molds. |
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Definition
The form and manner in which the spores are produced
- Appearance of the hyphae and mycelium |
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Term
| 1. Describe conidiospores and sporangiospores and name a mold that produces each of these. |
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Definition
- Conidiospores – borne externally in chains on an aerial hypha called a conidiophores. Finger like projections
o Produced by penicillin and aspergillus
- Sporangiospores – produced within a sac or sporangium on an aerial hypha called a sporangiophor.
o Produced by Rhizopus |
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Term
| 1. Define dermatophyte and list three common genera of dermatophytes. |
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Definition
- Group of molds that cause superficial mycoses of the hair, skin and nails and utilize the protein keratin.
- Microsporum , Trichophyton and Epidermophyton |
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Term
| 2. Name four dermatophytic infections and state how they are contracted by humans. |
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Definition
a. Tinea capitis – skin of the scalp , eyebrows and eyelashes
b. Tinea barbae – infection of the beared areas of the face and neck
c. Tinea faciel – infection of skin of the face
d. Tinea corportis – infection of skin regions other than the scalp, groin, palms and soles
- Acquired by contact with fungal spores from infected humans, animals or objects |
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Term
| 3. Describe macroconidia and microconidia. |
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Definition
- Macroconidia – large leaf or club shaped asexual spores
- Microconidia – small spherical asexual spores |
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Term
| 4. Describe how the following may be used to identify dermatophytes: potassium hydroxide preparations of tissue scrapings, DTM, and SDA. |
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Definition
- DTM –turns from yellow to red due to the alkaline end products being produced
- SDA – microconidia and macroconidia under a microscope they produce yellow to redish colonies |
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Term
| 1. Define dimorphic fungi and state how humans usually contract them. |
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Definition
| - Exibit two different growth forms. Grow as mold outside the body and as yeast inside. Inhaling spores from the mold form |
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Term
| 2. Name three common dimorphic fungal infections found in the United States, state how they are transmitted to humans, and indicate where they are found geographically. |
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Definition
a. Coccidioidomycosis – southwestern united states – inhalation
b. Histoplasmosis – great lakes region and the Mississippi and ohio river valleys. Inhalation
c. Blastomycosis – great lakes region and the Mississippi and ohio river valleys |
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Term
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Definition
| viruses that infect only bacteria |
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Term
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Definition
| small clear area on an agar plate where the host bacteria have been lysed as a result of the lytic life cycle of the infecting bacteriophages |
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Term
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Definition
| known bacteriophages are used to identify unkown bacteria by observing whether or not the bacteria lysed |
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Term
| 2. Describe the structure of the bacteriophage coliphage T4 |
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Definition
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Term
| 3. Describe the lytic life cycle of bacteriophages |
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Definition
a. Absorption
a. attachment sites on the bacteriophage tail absorb to receptor on the cell wall of a susceptible host bacterium
b. Penetration
a. A Bacteriophage enzyme drills a holein the bacterial cell wall ans the Bacteriophage injects its genome into the bacterium
c. Replication
a. Enzymes coded by the Bacteriophage genome shut down the bacteriums macromolecular synthesis. The Bacteriophage genome replicated and the bacteriums metabolic machinery is used to synthesize bacteriphage enzymes and Bacteriophage structural components
d. Maturation
a. The Bacteriophage parts assemble around the genome
e. Release
a. A Bacteriophage – coded lysozyme breaks down the bacterial peptidoglycan causing osmotic lysis of the bacterium and release of the intact bacteriophages
f. Reinfection
a. From 50 – 200 Bacteriophage may be produced per infected bacterium and they now infect surrounding bacteria |
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Term
| 4. Define viral specificity |
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Definition
| - A specific strain of Bacteriophage will only absorb to a specific strain of susceptible host bacterium. |
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Term
| 1. Name the bacterial family to which the most commonly encountered organisms isolated from clinical specimens belong. |
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Definition
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Term
| 1. List five characteristics used to place bacteria into the family Enterobacteriaceae |
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Definition
- Gram negative rods
- If motile they possess a peritrichous arrangement of flagella
- They are facultative anaerobes
- Most are oxidase negative
- All species ferment the sugar glucose
- Most reduce nitrates to nitrites |
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Term
| 3. State what infections are caused by Salmonella and by Shigella and how they are transmitted to humans. |
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Definition
a. Salmonella
a. Salmonellosis - transmitted to humans through inproperly refrigerated, under cooked or uncooked poultry, eggs, meat, dairy products, vegetables or fruit contaminated with animal feces.
b. Shigella
a. Shigellosis - |
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Term
| 5. Name five genera of Enterobacteriaceae considered as common opportunistic pathogens, state their normal habitat, and list four common types of opportunistic infections that they all may cause. |
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Definition
- Normal habitat – intestinal tract
o E. coli
o Proteus
o Enterobacter
o Klebsiella
o Citrobacter
o Serratia
- Urinary tract infections, wound infections, pneumonia and septicemia |
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Term
| 1. Name the most common non-fermentative gram-negative rod that infect humans and list five types of opportunistic infections it may cause. |
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Definition
- Pseudomonas aeruginosa
o Urinary tract infects
o Wound infections
o Pneumonia
o Septicemia
o Burn infections |
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Term
| 2. State 3 infections being caused with increased frequency by Acinetobacter |
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Definition
- nosocomial wound infections
- pneumonia
- septicemia |
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Term
| 1. State the usefulness of MacConkey agar and Cetrimide agar for the isolation of Enterobacteriaceae and Pseudomonas. |
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Definition
Mac Conkey agar
- selective medium used for isolation of non fastidious gram-negative rods
- crystal violet dye which inhibits growth of gram positive
- cetrimide
- inhibits growth of most bacteria other than Pseudomonas
- Different Pseudomonas turn it different colors or fluorescent |
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Term
| 1. State how to differentiate Pseudomonas aeruginosa from the Enterobacteriaceae using the following tests: |
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Definition
a. oxidase test
- taxo-N disc – if it turns pinkish in a few seconds then it is oxidase positive
o Pseudomonas aeruginosa is oxidase positive and most Enterbacteriaceae are oxidase negative
b. production of pigment and fluorescent products
- none of the Enterbacteriaceae produce pigment , Pseudomonas aeruginosa produces a green to blue water soluble pigment called pyocyanin. Pseudomonas aeruginosa also produced fluorescein that will fluoresce under short wavelength UV light
c. odor
- Enterobacteriaceae have a foul smell. Pseudomonas aeruginosa produces a fruity/grape juice like smell. |
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Term
| 1. Briefly describe the Enterotube® II. |
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Definition
| - Contains 12 different agars all in one tube. |
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