MICROBIOLO NU440/NUR4-Identification of Unknown Bacteria Notes

MICROBIOLO NU440/NUR4-Identification of Unknown Bacteria Notes Identification of Unknown Bacteria Notes: Which of the following would be most valuable to confirm the identification of microorganisms isolated during a food poisoning outbreak? Identification of microorganisms using microscopic, cultural, and physiological characteristics. What three main approaches can be used by microbiologists to identify microorganisms? Genetic, immunologic, phenotypic. Which method used to identify a microorganism causing an infection rely on the response of the host, rather than observation of the microorganism’s properties? Immunologic methods Genotypic identification methods examine the sequence of an organism, whereas Immunologic identification method uses antibody-antigen reactions to identify microorganisms. Which of the following is an example of a morphological characteristic that could be used in the bacterial identification process? Cell shape A particular microorganism can be distinguished from several closely related microorganisms by determination of its preferred growth temperature. This is an example of a cultural characteristic that can be used for identification. Which of the following are examples of physiological (biochemical) characteristics that could be used in the bacterial identification process? Ability to ferment glucose, ability to break down lipids, presence of specific enzyme. FALSE: Bergey’s Manual is an excellent resource for the identification of fungi and viruses as well as bacteria. TRUE: Bergey’s Manual contains information on the identification of bacteria only. FALSE: Bergey’s Manual of Determinative Bacteriology contains information related to the identification of only pathogenic bacteria. Bergey’s Manual of Determinative Bacteriology contains information regarding the identification of all types of culturable bacteria. Which of the following methods could be used to isolate bacteria from a mixture? Serial dilution followed by spread plating, loop dilution pout plating, streak plating Bergey’s Manual of Determinative Bacteriology first categorizes bacteria based upon which of the following characteristics? Cell shape, gram stain reaction TRUE: Multiple bacterial species can have similar staining reactions and microscopic morphology. What is the internationally recognized reference for bacterial classification and identification? Bergey’s Manual The ninth edition of Bergey’s Manual of Determinative Bacteriology was designed solely for identifying bacteria that have already been cultured and phenotypically examined. Which of the following types of media might be particularly helpful in the isolation of a single bacterial species from mixed bacterial culture? Differential, selective Which of the following is the quickest way to isolate bacteria from a mixture? Streak plating Which of the following would be a good starting point for identifying an unknown bacterium? Gram staining Identification of a bacterium can not be made on microscopic morphology alone because many microorganisms have a similar microscopic morphology. The name of the reference book that provides information about staining properties, morphology, and biochemical reactions of all known bacterial species is Bergey’s Manual. FALSE: A standard set of biochemical tests is used to identify all types of bacteria, regardless of morphological and cultural characteristics. Which of the following are advantages of using multi-test media or systems? Reduction in media usage, improved efficiency, reduction in time required for identification. A dichotomous key is a flowchart that can be used to identify an organism by making a series of choices until you arrive at one possibility. According to this flowchart, what test is most useful for distinguishing between Escherichia coli and Vibrio cholerae? Oxidase test How do you determine the strain of an sd? You use multiple biochemical tests and pre-existing knowledge to classify the bacteria. When choosing a biochemical test to perform on an unknown bacterium, you should consider which of the following? Choose an easy, rapid test that is applicable for its main group of bacteria Which of the following media tests can provide information on more than one biochemical characteristic? Kligler’s iron agar (KIA), SIM tubes Which of the following biochemical tests can be performed on a well-isolated colony and can provide immediate results without further incubation? Oxidase test Which of the following biochemical tests involve growth of an organism in a specific broth medium? Nitrate reduction test, phenol red, methyl red Which of the following media allows for the observation of multiple biochemical properties? SIM Inoculation of which tests involves stabbing the organism into the medium with an inoculating needle? SIM, KIA Which of the following is an agar plate that can indicate whether an organism ferments lactose? MacConkey medium Which of the following media allows for observation of several different biochemical properties? KIA The oxidase test determines the presence of cytochrome oxidase enzyme. This enzyme functions as part of the electron transport chain. Citrate = carbon source Ammonium - nitrogen source Bromothymol blue = pH indicator E. coli is positive on the nitrate reduction test after the addition of the first two reagents. This means E. coli reduces nitrate to nitrite. If an organism produces stable acids as an end-product of glucose fermentation, the methyl red test will be positive. Phenol red carbohydrate broths with Durham tubes can detect fermentation, acid production, gas production. Which of the following is true of a bacterial species that produces pink colonies when grown on MacConkey agar? They are lactose fermenters, they must be gram-negative bacilli. What causes the color change in a positive urease test? The production of ammonia from urea A KIA tube was inoculated with a bacterial isolate and incubated for 24 hours. At the end of incubation, the tube had a red slant and a yellow butt. What does this indicate about the biochemical properties of this bacterial species? Glucose was fermented, lactose was not fermented. What properties of a bacterial isolate can be detected using SIM medium? Indole production, hydrogen sulfide production, motility. Pseudomonas aeruginosa is an example of a bacterial species that is typically oxidase - positive. An organism can utilize citrate as its sole carbon source and ammonium salts as its sole nitrogen source. What change would you expect to see in a citrate slant inoculated with its organism? Color change from green to blue An organism has been inoculated into a nitrate broth and incubated for 24 hours. The nitrate reagents have been added but there was no color change. After the addition of zinc dust, the color changed to a bright red. Which of the following is the correct interpretation of these results? The organism did not reduce nitrate. Which of the following is detected by the methyl red test? Mixed acid fermentation Acid production in a phenol red carbohydrate broth is indicated by a color change from red to yellow. The color of lactose-fermenting colonies on MacConkey agar is dark pink-purple. An organism produces urease enzyme. Which of the following describes the color change expected in the test medium for this enzyme? Changes from yellow to bright pink. What biochemical properties can be detected using KIA medium? Hydrogen sulfide production, lactose fermentation, glucose fermentation Which of the following is a product of nitrate reduction that is directly detected via the nitrate reduction test? Nitrite Which of the following correctly describes E. coli? Would be pink on MacConkey agar plate after incubation, can move using its flagella, possesses the enzyme for tryptophan breakdown. E. coli would appear red in color and rod shaped under microscopic examination. Which of the following tests could have been used to determine that E. coli is a lactose-fermenter? Kia test, MacConkey agar Oxidase test  Blue = positive , White = Negative Phenol Red Broth  Yellow = positive, Red = negative MacConkey  Purple = positive, brown = negative Methyl red Broth  Red = positive, yellow = negative Sim agar  if red on top, little sediment, and then yellow = H2s neg --indole pos --motility pos  POSITIVE INDOLE// ring of brown, clearish-brown, ring of browh, dark brown all the way down = H2s Pos, indole - neg, motility - pos// brown ring, clearish-brown, ring of fading brown, swirls of brown down below = all negative = NEGATIVE