Last lab exam

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Manitol salt agar (MSA) is —–for staphylococci
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selective and differential. MSA allows any staph to grow on it and the agar around the staph will turn yellow.
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Coagulate test is considered definitive for testing—
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S. Aureus, this in the only one that is coagulase positive.
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The role of coagulase in the pathogenesis S. Aureus
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coagulase creates the fivrin clot for a barrier against the immune system.
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What does Alpha toxin do in the pathogenesis of S. aureus?
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Alpha toxin causes the cell lysis of RBC’s.
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lysis
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loosening,destruction, break up
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What are nasocomial infections?
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hospital infections
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Why are the staphylococci among the leading causes of nosocomial infections?
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because staph is found on 30% of us at all times.
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Why are staph infections becoming increasingly difficult to treat?
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They are becoming multi drug resistant
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What precautions are taken in nosocomial settings to prevent staphylococcal infections?
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Wash hands, antiseptics, sanitization and sterilization of equipment.
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Why might hospital staff be tested for nasal carriage of S. arueus?
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to let the hospital know which staff members may spread the infections to patients.
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When bacteria from a throat swab are streaked on blood agar, why is the agar stabbed several times with the loop?
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stabbing the agar makes the hemolysis look better.
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Differentiate between alpha and beta hemolysis…
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Alpha is partial hemolysis and will look green. Beta is complete memolysis and will create a clear halp around the organism.
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hemolysis
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Destruction of red blood cells
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What was Rebecca Lancefields contribution to the study of streptococci?
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Rebecca Lancefield cdivided the strep based on serological groups.
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serological
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different capsular types can be identified by ________ testing
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A throat swab is typically performed on an indivudual suspected to have streptococcal pharyngitis, or strep throat, On a blood agar what type of hemolysis would be expected in an individual with streptococcal pharyngitis?
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B hemolysis, a clear halo around the organism.
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What species causes streptococcal pharyngitis?
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streptococcal pharyngitis is usually caused by streptococcus pyrogenes.
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Why is it important to first confirm the presence of this species before administering any therapy?
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It may not be caused by a bacteria but by a virus and would not require antibiotics.
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Bacteria are isolated from the blood of a patient with septicemia. You would like to determine whether they are Streptococcus pyogenes or Staphylococcus aureus. What characteristics do the two species share?
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Both streptococcus pyogenes and staphylococcus aureus are gram positive.
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What tests would be useful for the differentiation of the two species, staph and strep?
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Staph are catalase positive and Strep are catalase negative.
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Name three test that are useful for the differentiation of S. pyogenes and S. agalactiae….
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Bacitracin suseptibility: pyrogenes is suseptible and agalactiae is not. Camp reaction: pyrogenes is negative and agalactiae is positive. Lancefield groups: pyrogenes is A and agalactiae is B.
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Name two tests that are useful for the differentiation of pneumococci and oral viridans streptococci?
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Optochin: pneumococci are susceptible and Viridans are not. Bile solubility: pneumococci are positive and Viridans are negative.
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What test can be performed to differentiate the enterococci from other group D streptococci?
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6.5% NaCl broth is used to differentiate enterococci (+) from group D strep (-).
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Name three enteric pathogens of primary medical importance.
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Salmonella, Shigella and some strains of E. Coli.
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What precautions can me taken to prevent infection and illness caused by enteric pathogens?
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Wash your hands and proter food handling.
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What selective agents are added to media to preferentially grow enterobacteria for study?
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Bile salts.
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What type of growth is inhibited from bile salts in media?
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Gram positive bacteria.
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What characteristic separates Salmonella and Shigella from most of the other enterobacteria?
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Salmonella and Shigella do not ferment Lactose.
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What media can be used for this differentiation between Salmonella and Shigella from most of the other enterobacteria?
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Glucose, Lactose and sometimes sucrose.
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What two characteristics separate Salmonella from Shigella?
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Salmonella are motile and produce hydrogen sulfide and Shigella are negative for both.
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What media can be used to differentiate between Salmonella and Shigella?
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SIM media for motility and looks black if H2S production.
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Which coliform bacteria are the most difficult to distinguish from the SS pathogens?
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Proteus
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What is the primary characteristic used to differentiate them?
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Proteus is positive for urea and the other two are negative
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Why is it important to complete morphological and cultural characterizations before pursuing physiological testing?
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This gets you started in the right direction and which test to use to determine your unknown.
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In regards to taxonomic classification of bacteria, what is the relationship between physiological and genetic differentiation of bacteria?
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Physiology is a display of what proteins and enzymes they are producing which comes from their genes.
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What is the function of bacterial exoenzymes?
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Exoenzymes breakdown macromolecules to smaller molecules that they can take into the cell body and use for metabolites.
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anabolism
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Anabolism is biosynthesis fo cell constituents. , Process of building up complex materials (proteins) from simple materials, The process that synthesizes a complex molecule from simpler compounds, thus requiring energy.
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Catabolism
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produce energy, carry out the breakdown of food materials., breakdown of more complex substances into simpler ones with release of energy
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fermentation
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the process by which cells break down molecules to release energy without using oxygen, a process in which an agent causes an organic substance to break down into simpler substances
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Why is the catalase test useful for the defferentiation of staphylococci from streptococci?
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Staph is catalase (+) and strep is catalase (-)
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How is acid or alkaline detected in a culture medium as an end product?
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a ph indicator such a phenol red in the broth or agar.
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Name two test for reactions that produce acid end products…
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KIA and fermentation of carbohydrates
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name two tests for reactions that produce alkaline end products…
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Urea hydolysis and litmus milk.
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What types of gases can be produced as a result of sugar fermentation?
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CO2
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How are these gases detected in fermentation reactions?
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Can be collected in a Durham tube.
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Name a nonfermentative test in which gas production indicates a positive test result…
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Nitrate reduction.
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A starch test you must add iodine to see if the starch was broken down. You should see……
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a halo for a positive result.
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A casein test should produce…
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a clear halo in the milk for a positive test result.
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A test for Triglycerides shoul turn….
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dark blue.
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Name two test that demonstrate hydrolysis of proteins or proteolytic digestion besides casein hydrolysis test.
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The Tryptophan to indole test and the Litmus milk test.
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Kligler’s iron agar and SIM are multiple test media, What test do these media have in common?
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Both test for cystein to hydrogen sulfide.
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What components of the media are included for this test?
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They both contain cystein and Iron Sulfate.
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Both Kligler’s iron agar and SIM are stabged but for different reasons, WHY?
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For Kligler’s it is to test for the fermentation of the sugars. For SIM it is to test for motility.
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What difficulties does one encounter when trying to differentiate bacteria on the basis of physiological tests?
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Contamination can give a false positive.
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In addition to the morphological, cultural, and physiological tests performed on an unknown, what tests can be conducted to further assist in it’s identification?
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DNA analysis.
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Kligler’s iron agar test media
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carbohydrate fermentation, hydrogen sulfide production
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MR-VP test medua
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2,3-butanediol fermentation, mixed – acid fermintation
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Phenol red lactose test media
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carbohydrate fermentation
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SIM medium test media
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hydrogen sulfide production, tryptophan degradation
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Simmon’s citrate agar media
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citrate utilization
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Skim milk agar media
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casein hydrolysis
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spirit blue agar media
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triglyceride hydrolysis
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alpha-naphthol reagent
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2,3-butanediol fermentation
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dimethyl-alpha-naphthylamine reagent
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nitrate reduction
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ferric chloride reagent
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phenylalanine deamination
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Gram’s iodine reagent
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starch hydrolysis
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hydrogen peroxide reagent
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catalase test
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Kovac’s reagent
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Tryptophan degradation
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Methyl red reagent
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mixed-acid fermentation
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N,N,N’,N’-tetramethyl-p-phenylenediamine dihydrochloride reagent
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oxidase test
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sulfanilic acid reagent
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nitrate reduction
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amylase enzyme
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starch hydrolysis
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cysteine desulurase enzyme
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hydrogen sulfide production
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lipase enzyme
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triglyceride hydrolysis
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protease enzyme
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casein hydrolysis
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tryptophanase enzyme
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indole
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urease enzyme
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urea hydrolysis
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2.3-butanediol product
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Voges-Proskauer test
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ammonia product
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phenylalanine deamination, tryptophan degradation, urea hydrolysis
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fatty acids product
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triglyceride hydrolysis
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indole product
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tryptophan degradation
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molecular oxygen product
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catalase
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phenylpyruvic acid product
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phenylalanine deamination

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