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Micro Lab Tests
Lab tests used for the identification of of a variety of microorganisms
| Question | Answer |
|---|---|
| What type of media is used in the Kirby-Bauer method of antimicrobial testing? | Mueller-Hinton II |
| Which method of testing takes into consideration the size of the zone of inhibition, molecular weight of the microbics, type of media, and the concentration of the bacterial culture when allowing lab results from one lab to another to be compared? | Kirby-Bauer Method |
| What is it called when a chemotherapeutic agent kills only the pathogen while leaving other bacteria unaffected? | Selective Toxicity |
| Compounds produced by several species of bacteria and fungi that serve to inhibit the growth of other bacteria are known as ___________. | Antibiotics |
| Overuse of antimicrobics that has led to the selection of resistant strains of bacteria that are immune to these substances is known as ___________. | Antibiotic resistance |
| What is done to identify an effective chemotherapeutic agent? | Susceptibility testing |
| What type of susceptibility testing is being used when a bacterial culture is spread over the surface of a plate of media and discs impregnated with various antimicrobics are placed on the plate? | Disc diffusion test |
| The size of the zone of inhibition is dependent on many variables which include ____________,_________________,and ____________. | Molecular weight of the antimicrobics, type of media, concentration of bacterial cultures |
| Which method of testing tests a single antimicrobic at varying levels of concentration and determines the minimal inhibitory concentration(MIC), or lowest level of a chemical that completely inhibits microbial growth? | Tube dilution test |
| What are two main reasons in which food contamination may occur? | Improper processing of vegetables containing endospores of clostridium botulinum allowing them to germinate & produce botulism toxins. Rupturing of the digestive tract during the processing of beef and poultry, releasing bacteria to be spread. |
| This type of media is both selective and differential. It is used for the isolation of Staphylococci from a mixed culture of bacteria. It used NaCl as a selective agent and phenol red to detect fermintation. | Mannitol Salt Agar |
| Which type of halophile is MSA selecting for? | Staphylococcus |
| Which color indicates that an organism ferments mannitol? | Yellow |
| If an organism in unable to ferment mannitol what color will the agar around that organism be? | Red |
| In a MSA test if there is little to no growth, no fermentation of mannitol, and inhibition by NaCl you would have to presume that the microorganism is _______________. | Not Staphylococcus |
| In a TSI test, what does a pH indication of yellow mean? | acidic |
| What are two main reasons in which food contamination may occur? | Improper processing of vegetables containing endospores of clostridium botulinum allowing them to germinate & produce botulism toxins. Rupturing of the digestive tract during the processing of beef and poultry, releasing bacteria to be spread. |
| This type of media is both selective and differential. It is used for the isolation of Staphylococci from a mixed culture of bacteria. It used NaCl as a selective agent and phenol red to detect fermintation. | Mannitol Salt Agar |
| Which type of halophile is MSA selecting for? | Staphylococcus |
| Which color indicates that an organism ferments mannitol? | Yellow |
| If an organism in unable to ferment mannitol what color will the agar around that organism be? | Red |
| In a MSA test if there is little to no growth, no fermentation of mannitol, and inhibition by NaCl you would have to presume that the microorganism is _______________. | Not Staphylococcus |
| In MSA, good growth, negative fermentation, and no NaCl inhibition or acid production indicates the inditification of _________. | Staphylococcus species |
| Staphylococcus aureus is able to grow in a high salt medium and ferment mannitol. If you were to look at a MSA plate, how would you be able to identify the Staphylococcus aureus from other strains of Staph or microorganisms? | There would be growth on the plate since it selects for Staphylococci and the color of the media would have turned yellow indicating the mannitol fermentation. |
| This type of agar contains bile salts and cystal violet to select for Gram-negative bacteria and lactose. | MacConkey Agar |
| What does MacConkey agar differentiate between? | Lactose fermenters and non-lactose fermenters |
| On a plate of MacConkey agar, what would indicate if there are organisms that are lactose fermenting? | The formation of colonies with pink to red centers. |
| White or translucent colonies on a plate of MacConkey agar would indicate what type of species? | Non-lactose fermenting species |
| The bacterial growth on a plate of MacConkey Agar should indicate that the bacteria is which of the following, Gram-positive or Gram-negative. | Gram-negative |
| This agar is selective for the isolation of Gram-negative enteric bacteria. | Eosin Methylene Blue Agar |
| Gram-positive bacterial growth is inhibited by which two dyes? | Eosin and Methylene Blue |
| Eosin Methylene Blue Agar is both selective and differential. What does it differentiate between? | Lactose fermenting bacteria and non-lactose fermenting bacteria |
| Blue-black colonies indicate ________ and colorless-amber colonies indicate ____________ in an Eosin Methylene Blue Plate. | lactose fermenting bacteria;non-lactose fermenting bacteria |
| What type of bacteria does Hektoen Enteric Agar select for? | Gram-negative enteric bacteria |
| What are two types of Gram-negative enteric bacteria that Hektoen Enteric Agar specifically selects for? | Salmonella and Shigella |
| What is used to inhibit the growth of Gram-positive bacteria in HEA? | Bile Salts |
| Which carbohydrates are included in the HEA media which are used to differentiate fermentative from non-fermentative bacteria? | Lactose, sucrose, and salicin |
| What color will e.coli appear on a HEA plate if they ferment any of the three carbohydrates? | Yellow to pink |
| Shigella bacteria, which do not ferment sugars in a HEA media will produce what color colonies? | Blue-green |
| S. Typhi does not ferment the sugars in HEA , therefore producing blue-green colonies. What would black centers in the colonies indicate? | Hydrogen sulfide production |
| Blood agar is used to observe what type of reactions? | Hemolytic |
| In beta hemolysis, what color is the zone around the bacteria? | clear |
| This is a combination differential media used to differentiate bacteria based on the reduction of sulfur, production of indole, and motility. | SIM Medium |
| In SIM Medium, bacterial growth that spreads from the central innoculation line, leading to cloudiness throughout the media indicates _________. | Motility |
| What has been produced when there is evidence of a black precipitate in the media in a SIM test? | Hydrogen sulfide |
| A positive reaction for Sulfur reduction | Black precipitate |
| A positive reaction for Indole production | Red ring |
| A positive reaction for motility | Growth radiating from stab line |
| What Reagent is used in a SIM Medium test? | Kovac's Reagent |
| TSI-Triple Sugar Iron Agar is a differential media used to evaluate fermentation of which three sugars? | sucrose, glucose, and lactose |
| Besides sugar fermentation, TSI also tests for _______ and __________. | Hydrogen sulfide and gas production |
| What does a crack in the media indicate? | Gas formation |
| Red slant/red butt | No fermentation |
| Yellow butt/red slant | glucose fermentation only |
| Black butt | hydrogen sulfide formation |
| Yellow slant | other sugar fermentation |
| yellow slant/yellow butt/crack | glucose, sugars, and gas formation |
| Which test determines if a bacterium is capable of a mixed acid fermentation? Methyl Red or Voges-Proskauer | Methyl Red |
| Which type of intestinal bacteria do the Methyl Red and Voges-Proskauer tests help indentify? Gram-positive or Gram-negative | Gram-negative |
| What does IMViC stand for? | Indole, methyl red, Voges-Proskauer, and citrate |
| This test detects the presence of the enzyme catalase, which catalyzes the breakdown of hydrogen peroxide to water and oxygen gas. | Catalase Test |
| The Catalase test helps in the differentiation of which two microorganisms? | Staphylococcus and Streptococcus |
| Starch agar is used in this type of test to distinguish bacteria that can hydrolyze starch from those that cannot. | Starch Hydrolysis |
Created by:
amykkey
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