Microbiology Flashcards
(131 cards)
1
Q
Ascospores
A
The sexual spore of Ascomycetes
2
Q
Bacilli
A
Rod-shaped bacteria
3
Q
Basidiospores
A
The sexual spore of basidiomycetes
4
Q
Capnophilic
A
An organism that required high levels of carbon dioxide for growth or for the enhancement of growth
5
Q
Cocci
A
Bacteria with a round shape
6
Q
Conidia
A
An asexual fungal spore that is deciduous and formed by budding ir splitting off from the summit of a conidiophore
7
Q
Endospores
A
A dormant form of bacterium
Intracellular refractile bodies that are resistant to heat, desiccation, chemicals, and radiation
Formed by some bacteria when environmental conditions are poor
8
Q
Facultative anaerobes
A
Bacteria that do not require oxygen for metabolism but that can survive in the presence of oxygen
9
Q
Fastidious microbes
A
Bacterial species with complex growth or nutritional requirements
10
Q
Flagella
A
Long, thin, helical structures that function in cell motility
11
Q
Hyphae
A
The body of a fungus that is created as a result of the linear arrangements of cells and that forms multicellular or multinucleate growth
12
Q
Mesophiles
A
Organisms with optimal growth temps between 25°C and 40°C
13
Q
Microaerophilic
A
An organism that requires oxygen for growth at a level that is less than that found in air
14
Q
Mycelium
A
Branching web made up of hyphae
15
Q
Obligate aerobes
A
Bacteria that require oxygen to survive
16
Q
Obligate anaerobes
A
Bacteria that are killed in the presence of oxygen or those with growth that is inhibited in the presence of oxygen
17
Q
Prokaryotic
A
Organisms whose cells lack a nucleus and other organelles
18
Q
Psychrophiles
A
Organisms that demonstrate optimal growth at cold temperatures (between 15°C and 20°C)
19
Q
Spirochetes
A
Any bacterium genus Spirochaeta that is mobile and spiral-shaped with flexible filaments
20
Q
Thermophiles
A
Organisms that undergo optimal growth at elevated temperatures
21
Q
Yeast
A
Any unicellular (usually oval) nucleated fungus that reproduces by budding
22
Q
Zygospores
A
The spores that result from the conjugation of 2 isogametes as occurs with certain fungi and algae
23
Q
Describe general characteristics of bacteria
A
Prokaryotic
Have specific requirements for temp, pH, oxygen tension, and nutrition
Methods of identification are based on criteria such as size, shape, arrangement, and chemical reactivity
24
Q
Describe the general characteristics of fungi
A
Heterotrophs
Most are multicellular except for yeast
Eukaryotic
Have hyphae to help with food
25
Describe the general characteristics of viruses
26
Discuss bacteria growth characteristics
Contain a single DNA strand and reproduce by binary fission
4 distinct phases:
Lag phase-time when bacteria are adapting their metabolism to use resources found in their new media
Exponential growth phase-bacteria starts generating until essential nutrients are depleted, toxic waste products accumulate, or space becomes limiting
Stationary phase-time when the total number of cells show no net increase or decrease
Death phase-decline in growth with spore formation
27
Describe the characteristic shapes of bacteria
Coccus (pl. Cocci): spherical cells
Bacillus (pl. Bacilli): shaped like rods or cylinders
Spiral (spirochetes): usually occur singly and can be subdivided into loose spirals
Coccobacillus(pl. Coccobacilli): small rod-shaped bacteria
Pleomorphic: shapes range from cocci to rods
28
Describe the characteristic arrangements of bacteria
Single: occur singly
Pairs: occur in pairs
Clusters or branches: occur in clusters, bunches, or groups
Chains: short or long chains
Palisades: arranged in a palisade or "Chinese letter" pattern
29
Discuss the significance of spore formation in bacteria
The presence and location of spores can help with the identification of bacterial species
Are resistant to heat, dessication, chemicals, and radiation
30
Discuss the significance of spore formation in fungi
Reproductive cells of fungi
Fungi can be differentiated on the basis of the structure of the hyphae and the presence of spores
31
Describe the reproduction of fungal organisms
Rely on both sexual and asexual reproductive systems
Asexual spores are either sporangiospores or conidia
Sexual spores include ascospores, basidiospores, and zygospores
32
Differentiate the 4 groups of pathogenic fungi
1. Basidiomycetes: mushrooms or club fungi
2. Ascomycetes: cup fungi
3. Zygomycetes: molds
4. Deuteromycetes: also known as Fungi imperfecti because no known sexual stage occurs
33
Discuss the general methods for viral specimen collection and handling
34
List the methods for the evaluation of samples with suspected viral pathogens
35
Agar
A seaweed extract that is used to solidify culture media
36
Alpha-hemolysis
Characterized by the partial destruction of blood cells on blood agar, which is evident as a greenish zone around the bacterial colony
37
Beta-hemolysis
The complete destruction of red blood cells on blood agar that creates a clear zone around the bacterial colony
38
Blood agar
An enriched medium that supports the growth of most bacterial pathogens
Usually composed of sheep's blood
39
Culture medium
A substrate for the growth of microbiology samples
40
Culturette
The trade name for a sterile swab in transport media that is used for collection of microbiology samples
41
Differential media
A bacterial culture method that allows bacteria to be differentiated into groups in the basis of their biochemical reactions on the medium
42
Enriched media
A type of culture media that has been formulated to meet the requirements of the most fastidious pathogens
43
Enterotubes
A commercially available modular system of culture media that contains media and reagents for numerous bacteriologic tests that can be performed simultaneously
44
Fastidious
A term used to describe a bacterial species with complex growth or nutritional requirements
45
Gamma-hemolysis
A term that describes a bacterial sample that produces no hemolysis on blood agar
46
Inoculating loops
a simple tool used primarily by microbiologists to take and transfer a small sample (inoculum) of a microorganism culture
47
MacConkey agar
An agar medium that contains peptone, lactose bile salts, sodium chloride, neutral red, and crystal violet that is used to differentiate lactose fermenter (coliforms) from non-lactose fermenter among enteric bacilli
48
Mueller-Hinton agar
A standard culture material that is used to evaluate the susceptibility of microorganisms to antimicrobial agents
49
Sabouraud dextrose agar
A type of agar growth medium containing peptones used to cultivate dermatophytes and other types of fungi
50
Selective media
A type of culture media that contains antibacterial substances that inhibit or kill all but a few types of bacteria
51
Thioglycollate
A liquid medium that is used to culture anaerobic bacteria to determine the oxygen tolerance of microbes
52
List the supplies needed for collecting and evaluating bacterial and fungal samples
Sterile cotton-tipped swabs
Dull scalpel blades
3- to 20-mL syringes and 21- to 25-guage needles
Sterile endotracheal tube or jugular or urinary catheter
Collection tubes and preservatives
Rayon swab in transport media
High-quality glass slides and coverslips
Inoculating loops or wires
Bunsen burner
Candle jar or anaerobe jar
A variety of culture media, including plates and broth
Antibiotic disks and dispensers
Gram stain or other stains needed
Scissors, forceps, and scalpel with blades
"Discard jar" containing disinfectant for contaminated instruments
Wooden tongue depressions for handling fecal specimens
Racks to hold tubes and bottles
Refrigerator "cold packs" and polystyrene shipping containers for samples that must be sent to reference laboratories
53
Discuss safety concerns related to the microbiology laboratory
All specimens should be treated as potentially zoonotic
Techs must wear PPE when handling specimens, including a lab coat, disposable gloves, and face masks
All PPE should be removed before leaving the lab
Contaminated materials must be decontaminated before disposal
No eating, drinking, smoking, handling contact lenses, or applying cosmetics when in the lab
54
Describes the types of media available for culturing bacteria
Transport media: designed to keep microbes alive while while not encouraging growth and reproduction
General purpose media:
Enriched media: basic nutrient media with extra nutrients added such as blood, serum, or egg
Selective media: contain antibacterial substances that inhibit or kill all but a few types of bacteria
Differential media: all bacteria to be differentiated into groups based on their biochemical reactions on the medium
Enrichment media: liquid media that contain nutrients that encourage the growth of desired organisms or that contain inhibitory substances that suppress competitors
55
List commonly used culture media and state the characteristics of the media
Blood agar: supports the growth of most bacterial pathogens
MacConkey agar: contain crystal violet (which suppresses the growth of gram-positive bacteria) to test for the primary identification of gram-negative bacteria
Mueller-Hinton agar: general-purpose medium that is used primarily for the performance of the agar diffusion antimicrobial sensitivity test
Dermatophyte test media: contains am indicator that turns red in the presence of most dermatophytes as well as antimicrobial agents to inhibit bacterial growth
56
Describe commonly available modular test media
57
Describe the culture media used for evaluation of fungal samples
58
Aspiration
The removal of fluids or gases from a cavity with the aid of suction
The removal of cells and tissue fluid from a lesion with the use of suction from a needle and syringe
59
Imprint
60
Swabbing
61
Discuss general guidelines for the collection of bacterial samples
1. A complete history and sufficient data must be obtained to help select the procedures most appropriate to isolate any organisms that may be present
2. The specimen must be collected aseptically
3. Multiple specimens must be kept separate to avoid cross-contamination
4. The specimen container is labeled
5. Adequate time should be taken to obtain accurate results
62
List the methods that can be used to collect samples for microbiology testing
Swabbing
Aspiration
Imprint
Biopsy
63
Describe the methods of collecting samples for fungal evaluations
Usually collected by plucking hairs and skin from the suspected lesion
64
List and describe aspects of sample collections for specific samples in a variety of sites
65
Acid-fast stain
A staining procedure for demonstrating the presence of microorganisms that not readily decolorized by acid after staining
This is a characteristic of certain bacteria
66
Capsule stain
A differential stain that is used to identify the cell capsules of pathogenic bacteria
67
Endospore stain
A differential stain that has been designed to identify the presence, location, and shape of spores in bacterial samples
68
Flagella stain
A differential stain to detect and characterize flagella if present on bacterial cells
69
Giemsa stain
A differential stain that is used for blood and bone marrow smears
Also used to visualize fungal organisms and mast cell granules
70
Gram stain
A differential stain that is used to classify bacterial samples in the basis of the chemical structure of their cell walls
71
Lactophenol cotton blue
A preparation of phenol, lactic acid, glycerin, distilled water, and cotton blue dye that is used to stain fungi in wet preparations
72
Potassium hydroxide
73
Simple stain
Typically used for yeasts
Ex. Crystal violet or methylene blue
74
Ziehl-Neelsen stain
One of the most widely used methods of acid-fast staining
It is commonly used during the microscopic examination of a smear of sputum that is suspected of containing Mycobacterium tuberculosis
75
List the stains that are commonly used for microbiology specimens
Gram stain
Ziehl-Neelsen (acid-fast) stain
76
Describe the components used in the Gram staining procedure
Primary stain (usually crystal violet)
Mordant: substance that fixes a dye to a structure (Gram's iodine solution)
Decolorizer (either 95% ethanol or acetone)
Counterstain (either basic fuchsin or safranin)
77
Describe the procedure for performing Gram staining
1. Place a drop of saline on the slide and transfer a small amount of the specimen
2. Allow the slide to air dry
3. Heat fix the slide
4. Place the slide over a staining rack
5. Pour the primary stain over the slide and let it sit for 30 seconds then rinse with water
6. Pour the mordant over the slide and allow it to sit for 30 seconds then rinse with water
7. Flood the slide with decolorizer until no more purple washes off then rinse with water
8. Add the counterstain and allow it to sit for 30 seconds then rinse with water
9. Air dry the slide or blot it dry with bibulous paper
78
Describe the use of potassium hydroxide when evaluating bacterial and fungal samples
Helps with bacterial classification when gram-variabke results are obtained
79
List and describe the staining procedures used for specific samples
80
Candle jar
A method of producing anaerobic conditions for the growth of anaerobic bacteria
81
Filamentous
82
Incubation
83
Mucoid
84
Presumptive identification
85
Quadrant streak
86
Rhizoid
Resembling a root or serving to anchor
87
Slant tube
88
Undulate
To have wavelike fluctuations or oscillations
89
Describe the general sequence used when identifying bacteria
1. Collect specimen
2. Direct Gram stain of specimen
3. Inoculate culture media
4. Incubate for 18-24 hours
5. Check for growth
A. Negative (no growth) - reincubate, recheck, then report as "no growth" if no growth is seen
B. Positive (colonies on media) - select representative colonies, perform Gram staining, then continue with identification procedures
90
Describe the quadrant streak method of inoculation
1. Use a sterile loop to remove a small amount of bacterial colony from the culture plate
2. Hold the loop horizontally against the surface of the agar to avoid digging into the agar when streaking the inoculum
3. Lightly streak the inoculating loop over one quarter (Quadrant A) of the plate using a back-and-forth motion
4. Pass the loop through a flame and allow it to cool
5. Place the inoculating loop on the edge of Quadrant A and extend the streaks into Quadrant B using a back-and-forth motion
6. Pass the loop through a flame and allow it to cool
7. Place the inoculating loop on the edge of Quadrant B and extend the streaks into Quadrant C using a back-and-forth motion
8. Pass the loop through a flame and allow it to cool
9. Place the inoculating loop on the edge of Quadrant C and extend the streaks into Quadrant D using a back-and-forth motion
91
Describe the procedure for the inoculation of slant tubes
1. Use a sterile bacteriologic needle to remove a small amount of the bacterial colony from the culture plate or to take a loop full from a broth culture
2. Stab the needle directly into the center of the agar and push the needle all the way down to the bottom of the tube
3. Withdraw the inoculating needle through the same path in the agar
4. Streak the slant using a back-and-forth motion starting at the bottom of the slant
92
Presumptive identification vs. Definitive identification
Presumptive identification relies on the color, colony morphology, growth on selective media, Gram stain and other enzymatic reactions to identify a bacterium, yeast or mold
Definitive identification of microorganisms is defined as identification to the genus or species lever that require additional tests (eg, biochemical panels, slide cultures)
93
Discuss aspects of the incubation of culture plates
94
List colony characteristics that are evaluated on bacterial colonies
Size (in millimeters or described as pinpoint, medium, or large)
Pigment
Density (Ex. Opaque, transparent)
Elevation (Ex. Raised, flat, convex, droplike)
Form (Ex. Circular, irregular, rhizoid, filamentous, undulate)
Texture (Ex. Glassy, smooth, mucoid, buttery, brittle, sticky)
Odor (Ex. Pungent, sweet)
Any hemolysis (Ex. Alpha, beta, gamma)
95
Describe methods for the culture of anaerobes
96
Antimicrobial disks
Paper disks impregnated with antibiotic agents and used during the performance of the antimicrobial sensitivity test
97
Antimicrobial susceptibility test
An in vitro test of the effectiveness of selected antimicrobial agents against microorganisms
98
Kirby-Bauer technique
A type of antimicrobial susceptibility test in which agar plated are inoculated with a standardized suspension of microorganisms and then antibiotic-containing disks are applied to the agar surface
99
Beta-lactamase
Enzyme produced by bacteria that are resistant to beta-lactam antibiotics
100
Direct sensitivity testing
An antimicrobial sensitivity test that involves the application of undiluted samples (Ex. Urine) directly to the Mueller-Hinton plate
101
Indirect sensitivity testing
An antimicrobial sensitivity trdt that involves the application of diluted samples (Ex. Urine) directly to the Mueller-Hinton plate
102
McFarland suspension
103
Minimum inhibitory concentration
The smallest concentration of an antibiotic that regularly inhibits growth of bacterium in vitro
104
Zone of inhibition
An area of no bacterial growth around an antimicrobial disc that indicates some sensitivity of the organism to the particular antimicrobial
105
Discuss the indications for performing antimicrobial sensitivity testing
Determines the resistance or susceptibility of bacteria to specific antimicrobials
106
Describe the procedure for performing an antimicrobial sensitivity test with the agar diffusion method
1. A pure culture inoculum is needed.
2. A sterile swab and 1 ml of sterile saline are needed.
3. A slightly cloudy suspension is made in the saline, using a small amount of isolated microorganism collected on a special inoculator wand that picks up a controlled number of microbes. This makes a cloudy suspension of a known density.
4. A sterile swab is used to streak the suspension evenly over the entire surface of the plate.
5. After the plate is dry, antibiotic discs, which are 2-mm diameter discs that have had antibiotics added to them (one antibiotic to a disc), are placed on the plate and spread apart from each other with a disc dispenser (a tool used to put the discs on the plates).
6. A sterile loop, needle, or forceps is used to lightly tap down on each individual disc. Once the disc has touched the agar, it shouldn’t be moved.
7. The plate is incubated overnight at 35° C (95° F) and read in the morning.
8. The area around the disc in which the bacteria didn’t grow is called the zone of inhibition. This zone’s diameter is measured, and it includes the diameter of the disc. There should be almost confluent growth between the zone of inhibition to the disc diameter.
9. If only one to two colonies grow, the inoculum is too light, and the plate needs to be restreaked.
10. Results for each antibiotic are measured in millimeters, compared to a standard chart, and rated as susceptible, intermediate, or resistant.
107
Describe the procedure for measuring the zone of inhibition and the significance of the measurement
The plates should be read after overnight incubation
The diameter of each inhibition zone is measured and recorded to the nearest millimeter
The zone sizes are divided into resistant or susceptible
108
Discuss the methods that are used to perform colony counts
After the colonies are incubated on a blood agar or another bonsekective agar plate, the colonies are counted and multiplied by 100 to determine the number of colony-forming units (CFUs) per mL of urine
109
California Mastitis test
An indirect test for bovine Mastitis that is based on the presence of a high leukocyte count in Mastitic milk
110
Catalase
An enzyme that catalyzes the breakdown of hydrogen peroxide into oxygen and water
111
Coagulase
A molecule produced by some bacteria that allows for the adhesion of fibrinogen to the cell surface
112
Hanging drop
A method of preparing specimens to evaluate motility
113
Indole
a crystalline organic compound with an unpleasant odor
114
Kovac's reagent
A substance used in bacteriology to detect the ability of bacteria to produce indole
115
Motility media
a semisolid media that is used to demonstrate motility in microorganisms
116
Oxidase
An enzyme that is present in some groups of bacteria and that is involved with the reduction of oxygen during normal bacteria metabolism
117
List and describe the methods for testing the motility of bacteria
Hanging drop prep
Wet prep
Motility media
118
List and describe the commonly performed biochemical tests
Catalase - is used to detect the presence of catalase enzyme by the decomposition of hydrogen peroxide to release oxygen and water; this test differentiates Staphylococcus from Streptococcus
Coagulase - Various strains of Staphylococcus can be distinguished from one another by incubating the microorganism in a test tube containing coagulase rabbit plasma
Oxidase - is used to determine if an organism possesses the cytochrome c oxidase enzyme; this test is used to assist in the identification of Pseudomonas, Neisseria, Alcaligens, Aeromonas, Campylobacter, Vibrio, Brucella and Pasteurella
119
Describe the procedure for performing the California Mastitis test
To perform the CMT:
1. Approximately 2mLs of milk is placed in four cups on the CMT paddle and an equal amount of reagent is added
2. The paddle is gently rotated for approximately 10 seconds un a circular pattern to mix
3. A score is then assigned for each quarter according to the chart of grading and interpretation
120
Describe each of the types of hemolysis
Complete hemolysis (beta-hemolysis): a clear, colorless zone surrounding the colony
Beta hemolysis: associated with pathogenic streptococci
Incomplete hemolysis: caused by partial destruction of red blood cells (alpha hemolysis)
Double zone of hemolysis: consists of an inner zone of clear hemolysis and an outer zone of partial hemolysis (delta hemolysis); very typical of coagulase-positive Staphylococcal isolates
No hemolysis: also referred to as gamma hemolysis
121
Dermatophyte test medium
A differential culture medium designed to support the growth of cutaneous fungal organisms and to inhibit bacterial growth
122
Potassium hydroxide
123
Ringworm
A group of fungal skin diseases that are caused by dermatophytes of several kinds
124
Sabouraud agar
Standard medium for isolating fungi
125
Wood's lamp
An ultraviolet light source that may be used to help diagnose fungal infections
126
Describe the procedure for preparing dermatophyte cultures
After the agar is inoculated, the top of the DTM plate should he left loose for air exchange
The culture should be incubated at room temp in the dark and observed daily for up to 2 weeks for growth and color change
127
Describe the procedure for microscopic evaluation of dermatophyte cultures
Direct mounts are prepared by mixing a small portion of the material in 2 or 3 drops of potassium hydroxide on a microscope slide (India ink can be added to the KOH solution to help with visibility)
A coverslip is placed over the wet mount and the slide is examined for the presence of hyphae in skin scales or the presence of spores on the outside surface of infected hair
128
Discuss the culture methods for nondermatophytes
Usually streaked out on blood agar or Sabouraud dextrose agar
129
List the characteristics of yeasts of veterinary importance
- Malassezia pachydermatis is frequently found in cases of external otitis. It’s seen in Gram-stained smears as an oval, budding yeast.
- Cryptococcus neoformans has abundant capsular material. Negative staining with India ink provides a black background that outlines the clear capsule. This yeast is sometimes the cause of nasal infections.
- Candida albicans is an opportunistic fungal pathogen; infections frequently involve mucous membranes. In wet mounts, unicellular budding yeasts without a capsule are present.
130
List the general characteristics of the systemic dimorphic fungi
Blastomyces dermatitidis- unencapsulated yeasts with thick, refractile double walls, 5-20 ųm in diameter
Coccidioides immitis- sphenules 10-100 ųm in diameter with doubly refractile cell walls and containing endospores, 2-5 ųm in diameter
Histoplasma capsulatum - tiny, ovoid, budding yeasts with narrow bases, 2-4 ųm in diameter
131
Describe the methods used to detect ringworm
Wood's lamp - look for fluorescence
KOH preparation - look for ectothrix spores or hyphae in skin scales
Culture - look for color change in the medium and colony growth
