Microbiology Differentiation Media Quiz

Phenylethyl Alcohol Agar (PEA) is selective for Gram-positive (G+) organisms and inhibits most Gram-negative (G-) organisms. It must be compared to a control plate to interpret results accurately.

MSA is used to select for halophiles with high salt concentration and differentiate based on their ability to ferment mannitol, making it a differential and selective medium.

MacConkey Agar (MAC) is both selective and differential. It selects for Gram (-) organisms by inhibiting the growth of Gram (+) organisms through the presence of crystal violet and bile salts. It is also differential as it tests the ability of organisms to ferment lactose and produces distinguishable results based on lactose fermentation.

Eosin-Methylene Blue (EMB) media is used as selective & differential media to inhibit G+ bacteria and differentiate based on the ability to ferment lactose &/or sucrose.

The setup for an Oxidation-Fermentation Test involves using two tubes: one covered with mineral oil to promote anaerobic growth and fermentation, while the other tube remains unsealed. This setup allows for observation of color changes based on different metabolic pathways.

Fermentation of sugars leads to the conversion of sugar into acid, alcohol, and gas, particularly CO2. This process does not result in the production of water, formation of protein, or generation of light.

CHO fermentation in PR Carbohydrate Broth produces an acidic environment, resulting in a yellow color change.

The correct answer refers to a series of biochemical tests used in identifying certain bacteria based on their ability to perform specific metabolic reactions. The other options are not related to MR-VP tests.

The correct method for performing MR-VP tests involves splitting the culture into two tubes and adding specific reagents to each tube, followed by a waiting period for color change.

To perform an Oxidase Reaction, it is essential to follow the specific steps mentioned in the correct answer. Mixing oxidase reagent with water, heating the sample, or dipping a metal rod in the sample are not the correct methods for conducting an Oxidase Reaction.

The nitrate reduction test specifically looks for the presence of nitrate reductase activity in microorganisms.

The Citrate Test using Simmons Citrate Agar tests for citrate permease in the presence of citrate as the only carbon source. The growth or color change observed in the agar indicates a positive or negative result for citrate utilization.

In the decarboxylation test, mineral oil promotes fermentation, resulting in alkaline products that turn purple. If an organism is a glucose fermenter but does not have decarboxylase, the result is yellow (-), and no color change indicates a negative result.

In the Starch Hydrolysis Test, a blue/black color change when iodine is added to starch indicates a negative result, meaning that starch is present. Any other color change, such as yellow, no change, or red, would indicate a positive result for starch hydrolysis.

Casein hydrolysis is detected by testing for the presence of casease enzyme that breaks down casein in milk.

The correct temperature for gelatin hydrolysis is 25C. Incubating at higher temperatures like 37C or 45C can lead to incorrect results. Room temperature may vary and not provide the ideal conditions for gelatin hydrolysis.

When DNase is combined with toluidine blue during DNA hydrolysis, the result is a pink halo indicating the presence of DNA degradation.

Lipid Hydrolysis is primarily tested using lipase tests which involve assessing the enzyme activity related to lipid breakdown. The incorrect answers are not relevant to testing lipid hydrolysis.

The PYR Test is primarily used for the presumptive identification of group A streptococci and Enterococci by testing for L-pyrrolidonyl arylamidase.

SIM medium is primarily used for testing for sulfide production, indole production, and motility in bacteria. It is not used for testing lactose fermentation, citrate utilization, or starch hydrolysis.

The correct answer describes the main purpose of KIA, which is to identify G-bacteria in the family Enterobacteriaceae using anaerobic and aerobic conditions with specific pH indicators.