What are possible sources of error in performing serial dilutions?
What are possible sources of error in performing serial dilutions?
There are many potential sources of error. Examples include: incorrect measuring of the sample or diluent; insufficient mixing; not switching pipettes between each step of the serial dilution; contamination because of poor sterile technique; or inadequate mixing of sample and molten agar in the Petri dish.
What is the main disadvantage of the serial dilution technique?
Serial dilution processes face two major challenges. The first is error propagation across columns or rows. With each sequential serial dilution step, transfer inaccuracies lead to less accurate and less precise dispensing. The result is that the highest dilutions will have the most inaccurate results.
How do you solve a serial dilution problem?
In serial dilutions, you multiply the dilution factors for each step. The dilution factor or the dilution is the initial volume divided by the final volume. For example, if you add a 1 mL sample to 9 mL of diluent to get 10 mL of solution, DF=ViVf = 1mL10mL=110 .
What is dilution error?
Dilution errors are those errors associated with the sample preparation from the time a sample is gathered until the time the organisms are either counted or identified. Without proper training, the opportunity for error could be substantial, and the impact may vary from small to great.
How can dilution error be reduced?
The most common control strategies to prevent or reduce dilution error are analyst training and expanded use of liquid handlers [20]. However, analyst training is costly, time-consuming, variable in quality and inherently limited in its effect.
What is the major disadvantage of direct microbial counts compared with the serial dilution agar plate procedures?
What is the major disadvantage of microbial counts performed by methods other than the serial dilution-agar plate procedure? The serial dilution agar plate procedure only accounts for living viable cells while other methods count for both living and dead cells.
Are serial dilutions more accurate?
The more evenly spaced the calibration standards are over this range, makes the results of the analysis more reliable. Evenly spaced calibration standards are easier to prepare using serial dilution.
What are the advantages and disadvantages of the serial dilution agar plate?
The advantage of the serial dilution-agar plat-ing procedure is that the cell count represents only viable cells. The disadvantage of this method is that it requires an incubation period that precludes the ability to obtain immediate results.
What is serial dilution in microbiology PDF?
Serial dilution is a common technique used in many immunologic procedures. A small amount of serum or solute can be serially diluted by transferring aliquots to diluent. One of the most common series doubles the dilution factor with each transfer (1:2, 1:4, 1:8 …).
What is serial dilution method?
A serial dilution is the stepwise dilution of a substance in solution. Usually the dilution factor at each step is constant, resulting in a geometric progression of the concentration in a logarithmic fashion. A ten-fold serial dilution could be 1 M, 0.1 M, 0.01 M, 0.001 M …
How does dilution affect absorbance?
According to this law, absorbance and concentration are directly proportional to each other. If we increase the original concentration, the absorbance increases and if we dilute the solution (which means decreasing the original concentration), the absorbance will decrease in direct proportion.
What are the benefits of performing a serial dilution?
It helps to reduce a dense culture of cells to a more usable concentration.
What is the importance of serial dilution?
Purpose of Serial Dilution In microbiology, it allows for the estimation of the concentration (number of organisms, bacteria, viruses, or colonies) of an unknown sample by backtracking the measured concentration of the most diluted solution to the unknown concentration.
What is the major disadvantage of microbial counts performed by methods other than the serial dilution?
What are the disadvantages and advantages of viable plate count?
Despite its shortcomings, the viable plate count is a popular method for determining cell number. The technique is sensitive and has the advantage of only counting living bacteria, which is often the important issue. Any concentration of microorganism can be easily counted, if the appropriate dilution is plated.
Why is a series of dilutions more accurate and convenient?
Calibrations Solutions More Evenly Spaced The more evenly spaced the calibration standards are over this range, makes the results of the analysis more reliable. Evenly spaced calibration standards are easier to prepare using serial dilution.
What is the main advantage of counting the bacteria in a specimen using serial dilution?
We use serial dilutions to create decreasing concentrations of the original sample that are then plated so that a plate will be created with a low enough number of bacteria that we can count individual colonies. From that number, we can calculate the original cell density in the broth.
What are the disadvantages of dilution plating when using soil samples?
Dilution plating is a common, inexpensive, and simple method for bacterial enumeration, but it does suffer from several drawbacks. The soil should not be allowed to settle during dilutions, which could lead to biased growth. Some soil bacteria will not culture on the plates, or grow too slow to be observed.