Micro Lab Quiz 2

MacConkey agar (MAC) is most commonly used for the selective isolation of (a.)_____________ and differentiate them based on (b.)____________ resulting in a color change.

b. Lactose fermentation a. Gram negative species

In the serial dilution procedure of this laboratory exercise the dilution was increased with each transfer to the next tube by a factor of________?

10

In a serial dilution, the final dilution factor performed was 1:100,000. After 48 hours incubation @ 37oC there were 190 colonies counted on the plate. What was the concentration of bacteria in the original undiluted sample?

19,000,000 cfu/mL

A fundemental technique important in the laboratory and used by Microbiologists for a variety of procedures such as, transferring cultures, inoculating media and isolation of pure cultures is known as?

Aseptic technique

Differential media is a type of specialty media which?

Contain specific dyes that cause a color change as different bacteria grow and produce waste products.

This agar plate has only one species of bacteria growing on it. This type of agar can best be described as___________?

Differential

When performing a serial dilution, a student forgot to change the pipette and used the same pipette for every .5 mL transfer of the solution from tube to tube. Would these results be accurate and what would you predict the outcome would be?

These results would be inaccurate because the extra culture on the inside and outside of the pipette would increase the concentration of the next tube beyond the factored amount.

After performing a serial dilution a student counted 9 colonies on the 1:100,000 plate and 21 colonies on the 1:10,000 plate. Was this an accurate serial dilution? Why or why not?

This was not an accurate serial dilution because the number of colonies counted on the 1:100,000 plate was not within the target window and the difference in the count between the two plates was not close to a factor of 10.

Aseptic technique is a fundamental and important laboratory skill in the field of microbiology. Choose some examples of how or why aseptic technique would be used in a laboratory.

-Aseptic technique prevents microbes used in the laboratory from accidentally being released into the environment and/ or infecting people working in the laboratory. -Proper aseptic technique prevents contamination of cultures from foreign bacteria inherent in the environment. -Using proper aseptic technique can greatly minimize or even eliminate the risk of contamination.

List 4 protocols that must be followed for the collection of a biological specimen in order to obtain a timely and valid laboratory result.

-Samples must be collected using proper collection techniques. -It must be collected in the proper container. -It must be collected in the presence of the patient and labeled with 2 identifiers (such as patient name and number). -Collected samples must be transported to the laboratory as soon as possible.

The amount of growth indicated by the arrows on this agar plate could best be described as (zone A)___________ and (zone B)___________?

zone A = 4+ growth zone B = 1+ growth

This specialty media was inoculated with 3 different species of bacteria (one type in each zone). Based on these results________________.

-the color change occurred due to a dye or indicator that was added to the media during preparation. -a growth inhibitor was used and resulted in no growth of one of the species.

Lysis of red blood cells occurs but the iron in the RBC is not consumed as a food source

Alpha

The appearnce of a greenish color with bacterial growth on blood agar

Alpha

In this type of hemolysis a clear zone is left behind in the agar

BETA

This is the complete lysis of red blood cells on blood agar where all of the contents of the cell were consumed as a nutritional source

Beta

This is due to the lysis of red blood cells, in Blood Agar, and the complete absorbance of the nutrients from the red blood cells, leaving behind a clear zone on the agar.

Beta hemolysis

Identify the type of hemolysis with the appropriate letter.

C- Gamma A- Beta B- Alpha

Patient samples, after specimen collection, that were transported promptly but inaccurately labeled will be tested anyway.

FALSE

Bacteria is growing on the agar but there is no change in the appearance or color of the blood agar and no lysis of red blood cells

Gamma

Concerning the inoculation techniques discussed in this lab, one difference between the "Spread Plate Method" and the "Streak Plate Method of Isolation" is___________ and one similarity is_________?

One difference between the two techniques is that the "Spread Plate Method " is used to evenly distribute the bacteria across the entire plate and a similarity is the end result should produce pure colonies in both methods.

An agar that contains a dye and/or indicator and a growth inhibitor as part of its ingredients can best be described as.

Selective and Differential

Zone 1, 2 and 4 on this plate demonstrate 4+ growth. There is no growth on zone 3. Based on the results of this agar plate, this type of media could best be described as?

Selective and Differential

A method used to dilute a substance in a stepwise manner into a solution with a constant dilution factor is known as?

Serial dilution