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Lab Exam 2
Pathogens
102
Microbiology
Undergraduate 3
11/28/2011

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Term
The process of identifying an “unknown” bacterium is a rational and sequential procedure.
What is the 1st step in attempting to identify the “unknown”?
Definition
Obtaining a pure culture
Term
What is the 2nd step in identifying an unkown?
Definition
Performing a gram stain
Term
List 3 pieces of information that can be determined from a Gram stain
Definition
1. Gram reaction
2. Cell shape
3. cell arrangement
Term
list the 4 genus mentioned in the lab manual that are able to fix nitrogen
Definition
Rhizobium, Azobacter, Cyanobacteria, Clostridium
Term
Symbiosis
Definition
Living together in the same environment
Term
Symbioants
Definition
organisms that live together in a particular environment
Term
name 2 enzymes that are involved in notrogen fixation
Definition
Nitrogenase and Transaminase
Term
name two end products of nitrogen fixation
Definition
Ammonia and Amino Acids(-> proteins)
Term
List 3 types of symbiotic relationships and describe each one
Definition
1. commensalism: the microbe benefits, the host is neither benefited or harmed
2. mutualism: the host and microbe both benefit each other
3. parasitism: the microbe benefits at the expense of the host
Term
Rhizobium and legume plants are an example of which type of symbiotic relationship? why?
Definition
Mutualism; because the Rhizobium cannot fix nitrogen without without a legume and it also obtains energy from carbohydrates synthesized by the plant, and the fixation gives the legume nitrogen that it can use for growth of plant parts
Term
what is the Gram reaction and cell shape of Rhizobium cells?
Definition
Gram-negative rods
Term
List 6 characteristcs of Staphylococci
Definition
1. Saprophytes and parasites of skin and mucus membranes
2. Gram-positive cocci arranged in clusters
3. Medium sized, off white or yellow colonies
4. faculative anaerobes
5. tolerant of high NaCl concentration
6. produces catalase
Term
Where are Staph found in the body?
Definition
skin and mucus membranes, especially nasopharynx and uppermost part of pharynx that is continuous with nasal passages
Term
Give one example of a pathogenic Staphylococcus
Definition
Staph aureus
Term
Give 2 examples of a Staph that is non-pathogenic
Definition
Staph epidermis and Staph saprophyticus
Term
what test can be used to differentiate between the pathogenic and non-pathogenic Staph?
Definition
the coagulase test
Term
List 4 diseases caused by Staph aureus
Definition
1. wound infections
2. pneumonia
3. toxic shock syndrome
4. food poisening
Term
List 7 characteristics of Streptococci
Definition
1. Saprophytes and parasites
2. Gram-positive coccie arragned in chains or pairs; small white colonies
3. More fastidious
4. faculative anaerobes
5. lactose fermenters
6. not catalse producers
7. no NaCl tolerance
Term
Streptococci are divided into 3 groups according to their type of hemolytic reaction. List and describe these groups
Definition
1. Alpha: hemolysins partially lyse red blood cells and reduce hemoglobin(red pigment) to methemoglobin(green pigment)
2. Beta: hemolysins completely lyse RBCs and decolorize the hemoglobin
3. Gamma: no lysis occurs
Term
3 characteristics of Hemolysins:
Definition
1. lyse RBCs
2. are produced by pathogenic bacteria
3. play a role in the virulence of the pathogenic organisms via aidning the infecting organism to escape some of the hosts productive mechanisms(such as blood clot formation)
Term
what is the function of the coagulase enzyme?
Definition
clots blood plasma without using thrombin
Term
How is the result of the mannitol fermentaion interpreted?
Definition
If mannitol is fermented, the agar turns from pink to yellow
Term
what is the correlation between the Mannitol Fermentation test and the Coagulase test?
Definition
if one is positive, the other one will be too
Term
Describe the Bile-Esculin test
Definition
Group D Strep can hydrolize bile-esculin into eculectin and glucose. Esculectin can be visualized by adding gerric citrate, which forms a black/grey complex
Term
Explain the principle of the NaCl tolerance test
Definition
Group D Strep arethe only group of strep resistant to Salt
Term
How is the NaCl tolerance test interpreted?
Definition
Positive result= turbidity in NaCl broth and/or deep purple color change to light purple
Term
List 7 characteristics of the enteric organisms
Definition
1. Gram (-)
2. faculative anaerobes
3. oxidase negative
4. catalse (+)
5. non-spore forming
6. ferment glucose
7. rod shaped
Term
What 2 diseases are caused by genus Escherichia?
Definition
Typhoid fever and acute gastro enteris
Term
which 3 genuses are frequently found in Urinary Tract infections but not GI tract?
Definition
Hafnia, Morgonella, Providencia
Term
Coliform
Definition
Gram-negative, non-spore forming, faculatively anaerobic rods that can ferment lactose
Term
Differential media
Definition
contains ingredients designed to elicit a specific biochemical of physiological response, allowing different groups to be differeintiated
Term
List 3 examples of differential media and what the differentiate
Definition
1. MacConkey Agar- lactose fementers
2. Bile Esculin Agar- Esculin hydrolysis
3. Mannitol Salt Agar- mannitol fermentation
Term
Selective media
Definition
contains components that inhibit growth of unwanted bacteria, thus selecting bacteria that are resistant to the components
Term
some media are both selective and differential, give 2 examples
Definition
MacConkey Agar and Mannitol Salt Agar
Term
TSI(Triple Sugar Iron) agar can detect:
Definition
1. glucose, sucrose, lactose fermentation
2. gas production
3. H2S production
Term
A yellow butt in the TSI agar indicates:
Definition
glucose fermentation
Term
a yellow TSI slant indicates:
Definition
sucrose/ lactose fermentation
Term
IMVIC is a combination of which 4 tests?
Definition
Indole, Methyl-Red, Vogues-Proskauer, Inorganic Citrate
Term
The enterotube has 12 chambers and can perform how many tests simultaneously?
Definition
15
Term
The enterotube can identify the level of...
Definition
species
Term
Non-invasive organisms
Definition
do not invade the tissues and cause damage, instead they reside on the surface
Term
opportunists
Definition
can cause disease of the host defenses are lowered of if the balance between bacteria and normal flora is disrupted
Term
pathogenic organisms
Definition
sometimes invade the body and cause disease of they can get past defenses
Term
What is the one weakness of the Kirby-Bauer Disc method?
Definition
it does not determine if an organism is bacteriostatic of bacteriocidal
Term
Bacteriostatic organism
Definition
inhibits growth but does not kill
Term
Bacteriocidal organism
Definition
inhibits growth and induces killing
Term
List the 9 factors that affect the size of inhibition zones
Definition
1. Sensitivity or organism
2. molecular size
3. concentration of agent
4. density of culture
5. rate of diffusion of agent
6. size of inoculum
7. time of incubation
8. temperature of incubation
9. interactions between agent and medium
Term
Name two antibiotics that are small in size
Definition
Pecicillin and ampicillin
Term
Name 2 antiobiotics that are large in size
Definition
Poolymyxin B and bacitracin
Term
MIC (minimal inhibitory concentration)
Definition
lowest concentration that prevents visible growth but not killing
Term
MBC (minimal bacteriocidal concentration)
Definition
lowest concentration that prevents visible growth and induces killing
Term
Bacteriolytic
Definition
lyses cells and is observed as a decrease in cell number or turbidity
Term
Synergism
Definition
the antimicrobial effect of two drugs used simultaneously is greater than tha of the drugs when used seperately
Term
antagonism
Definition
combination of two drugs interferes with each other's mechanisms and renders them ineffective
Term
Citrate Utilization

-how does the medium change and why?
-what is the indicator?
Definition
Produce NH3(alkaline) --> Simon citrate slant medium changes green to blue due to a rise in pH. Bromothymol blue is the indicator
Term
How does Carbohydrate Fermentation and Gas Production in Durham tubes? What is the indicator?
Definition
the tube changes from green to yellow due to a drop in pH. BTB is the indicator
Term
Indole Production Test
Definition
indole--> intermediate metabolite in breakdown of tryptophan(amino acid)
-presence of enzyme tryptophase
-Kovac's reagent--> reacts with indole-->red
Term
Methyl Red Test
Definition
tests for mix acids production from glucose fermentation. Turns red at pH below 4.4. Large acid: alcohol ratio. equal C02:H2 ratio. MR-VP medium-->add methyl red--> red is positive result. indicates the fermentation of glucose
Term
Vogue-Proskauer Test (Butanediol Fermentation)
Definition
also indicates fermentation of glucose to 2,3 butanediol and ethanol. detects the presence of acetoin. high alcohol:acid ratio. large amount of gas is produced, large C02:H2 ratio. MR-VP medium, add Barritts A and B--> wait for 20 minutes--> pink/red = positive
Term
3 Categories of Biological and Enzymatical Reactions Used to Identify Bacteria
Definition
1. Nutrient Requirements
2. Metabolic Intermediate or End Products
3. Presence of Specific Enzymes
Term
2 Tests Used to Determine the Nutrient requirements of a Bacterium
Definition
1. Citrate test
2. sugar fermentation test
Term
Citrate test
-what does it determine?
-what is the medium?
-what is the indicator?
-how are results interpreted?
Definition
-tests for the ability to use citrate as the sole source of carbon
-Simon agar is used
-Bromothymol Blue is the indicator
-Change from green to blue (bc of pH increase) is a positive result
Term
Sugar Fermentation test
-what does it determine?
-what is the medium?
-what is the indicator?
-how are results interpreted?
Definition
-tests for Carbohydrate fermentation and gas production in a Durham tube
-tube changes from green to yellow (+ result) due to decrease in pH
-Bromothymol blue is the indicator
-if gas is produced, it is shown by a trapped bubble
Term
3 Tests that Determine the Metabolic Products of an Organism
Definition
1. Indole test
2. Methyl Red test
3. Vogues-Proskauer test
Term
Indole Test
-what does it test for?
-what reagent is used?
Definition
-tests for the production of indole from tryptophan (an amino acid)
Tryptophase breaks down tryptophan into indole, pyruvic acid, and ammonia. Indole is what is what is being tested for, but it implactes the presence of tryptophase
-the presence of indole is seen by adding Kovac's reagent, which reacts with indole and creates a red complex
Term
Methyl Red test
-what does it test for?
what is the indicator? Medium?
-how are results interpreted?
Definition
-tests for strong acid production from fermentation. Methyk red organisms produce large amounts of lactic, succinic, and acetic acid --> low pH. the produce small amount of ehtanol --> large acid:alcohol ratio
-if an organism has formic hydrogenase, then equal amounts of CO2 and H2 are produced.
-indicator methyl red turns red at or below pH 4.4
-MR-VP broth is used (a glucose broth)
Term
Vogues-Proskauer Test
-what does it indicate?
-what does it detect?
-what medium is used? reagent?
-how are the results interpreted?
Definition
-indicates fermentation of glucose to 2,3 butanediol and ethanol
-detects presence fo acetoin
-high alcohol: acid ratio
-large amounts of gas produced, large CO2:H2 ratio
- MR-VP medium used
-add Barrits A and B --> wait 20 minutes --> pink/red= positive
Term
3 tests that indicate the presence of specific enzymes
Definition
1. Oxidase test
2. Catalase test
3. Urease test
Term
Oxidase test
-what does it determine?
-what dye is used?
Definition
-determines if organisms have Cytochrome C. Oxidase
-use a colorless dy: p-phenylenediamine dihydrochloride as an artificial electron donor
-->dye is oxidized--> blue/black color
Term
Catalase test
Definition
-catalase converts hydrogen peroxide to oxygen and water
-usually facultative aerobes and obligate aerobes have catalase
-add H2O2, ifi t bubbles, catalase is present
Term
Urease Test
Definition
-determine ability of organism to hydrolyze urea
-urease converts urea broth into ammonia and CO2
-hot pink color (due to pH increase) indicates positive result
Term
Cysteine Desulfurase Test
Definition
-detection of H2S production
-Kligler's iron agar (KIA) is used
-dark precipitate indicates H2S production
-if yellow
Term
phages
Definition
bacterial viruses
Term
essential constituents
Definition
nucleic acid and proteins- basic structure --> capsid or shell which encloses the nucleic acids (either DNA or RNA)
Term
2 major qualities of a virus
Definition
1. possesion of its own genetic material, which, on its own, behaves as part of the host cell
2. possesion of extracellular infective state, represented by specialized onjects, the virions, which are produced in the cell under genetic control of the virus itself and serve as vehicles for introducing the viral genome into other cells
Term
plaque
Definition
a clear spot on a bacterial lawn that contains no bacteria bc all the cells have been lysed
Term
3 different viral shapes
Definition
-helical: spring shaped
-polyhedral: many sided
-binal: polyhedral head w/ helical tail(nucleic acid in head)
Term
3 types of T type coliphages
Definition
a. T even phages: similar in geneitc constitution and serologic properties
-->pyrimidine, 5-hyroxymethylcytosine replaces cytosine
b. T5: resembles T even phages except has regular cytosine
c. T1, T3, T7: seroligically an genetically unrelated to both one another and the T-even phages
Term
5 Stages of phage infection
Definition
1. adsorption to specific receptor sites on bacterial cell
2. penetration of phage nucleic acid into bacterial host, protein coat remaining outside
3. intracellular development: phage replication, biosynthesis
4. maturation
5. lysis --> release
Term
Lysogeny
Definition
viral nucleic acid persists in host for many generations(or indefinitely). bacterial host functions normally, viral nucleic acid is transmitted successively through many bacterial generations
Term
temperate phages
Definition
bacteriophages that cause lysogeny
Term
lysogens/ lysogenic strains
Definition
bacterial hosts of lysogeny
Term
prophage
Definition
latent, non-infectious form which is carried in lysogenic bacteria
Term
Rhizobium
Definition
gram(-) rods
symbiotic organism that invades root hairs
nitrogen fixing
Term
symbiosis
Definition
living together
Term
2 enzymesi nvolved in notrogen fixation
Definition
transaminase & nitrogenase
Term
2 final end products of Nitrogen fixation
Definition
Amino Acids & proteins
Term
whati s the shape and gram reaction of Staphylococci?
Definition
Gram (+) cocci
Term
what is the arrangement and color of Staphylococci colonies?
Definition
golden/ off white clusters
Term
Is Staph tolerant of NaCl?
Definition
yes, high NaCl (7.5%)
Term
where is Staph found?
Definition
skin follicles and mucus membranes
Term
Staph's oxygen requirement is...
Definition
facultative anaerobe
Term
pathogenic Staph
Definition
Staph. aureus
Term
non-pathogenic staph
Definition
Staph epidermidis and Staph saprophyticus
Term
what test is used to differentiate between pathogenic and non-pathogenic Staph?
Definition
coagulase test
--> (+)test = pathogenic
-->coagulase converts fibrinogen to fibrin and clots plasma
Term
S. aureus causes which diseases?
Definition
wound infections, pneumonia, toxic shock syndrome, food poisening
Term
S. epidermidis causes...
Definition
hospital acquired infections
Term
S. autotrophyticus causes...
Definition
urinary tract infections (UIT)
Term
what is the gram reaction and shape of Streptococci?
Definition
Gram (+) cocci
Term
Strep is catalase...
Definition
negative
Term
Staph is catalase...
Definition
positive
Term
is Strep NaCl tolerant?
Definition
nope (excpet in group D)
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