Praktikum Mikrobiologi: Percobaan 5 (Uji Aktivitas Dilusi Cair)

Summary

This video tutorial demonstrates a practical test for evaluating the antibacterial activity of chloramphenicol using the liquid dilution method. The experiment involves preparing bacterial suspensions, diluting the antibiotic into various concentrations, and testing its ability to inhibit bacterial growth. The minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) are determined by observing the turbidity in the test solutions. The process also includes controls for comparison. After incubation, the results are analyzed to see if any bacterial growth is inhibited, offering insights into the antibiotic's effectiveness.

Takeaways

• 😀 The purpose of the experiment is to test the antibacterial activity of chloramphenicol against *Staphylococcus aureus* using the liquid dilution method.
• 😀 The two key parameters to measure are the Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) of the antibiotic.
• 😀 Materials required include bacterial suspension, chloramphenicol solutions at various concentrations (2%, 1%, 0.5%, and 0.25%), and aquades (sterile water).
• 😀 The experiment uses a series of dilution steps to prepare different concentrations of chloramphenicol in separate tubes.
• 😀 The bacterial suspension is added to each chloramphenicol solution to test the antibacterial effect at different concentrations.
• 😀 The solutions are incubated at 30°C for 18-24 hours to observe bacterial growth inhibition.
• 😀 Control solutions, including aquades (without bacteria) and bacterial suspension (without chloramphenicol), are used for comparison.
• 😀 After incubation, clear solutions indicate the MIC, meaning the concentration of chloramphenicol that inhibits bacterial growth.
• 😀 To determine the MBC, a streaking test is performed by transferring some of the incubated solution to an agar plate and checking for bacterial growth.
• 😀 Unexpected results may occur, such as bacterial growth at higher concentrations, highlighting the variability of practical experiments.
• 😀 The experiment underscores the importance of precise handling and interpretation of results, as actual outcomes may differ from initial hypotheses.

Q & A

What is the objective of the antibacterial activity test discussed in the script?

The objective of the test is to determine the ability of a test substance or antibiotic to inhibit bacterial growth by identifying the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against the bacterial species being tested.

Which bacterium species was used in the test?

The bacterium used in the test is Staphylococcus aureus.

What is the purpose of the McFarland standard in the test?

The McFarland standard is used as a comparison solution to adjust the bacterial suspension to a specific turbidity, ensuring that the bacterial concentration is consistent for the test.

How are the different concentrations of the chloramphenicol solution prepared?

The chloramphenicol solution is prepared in various concentrations by first dissolving 30 mg of chloramphenicol in 1.5 mL of aquadest to make a 2% solution. Then, this solution is serially diluted to create concentrations of 1%, 0.5%, and 0.25%.

What is the role of the micro-pipette in the experiment?

The micro-pipette is used to transfer precise volumes of the chloramphenicol solution and bacterial suspension into the test tubes, ensuring accurate concentration and consistency across all samples.

How is the bacterial suspension introduced into the test solutions?

The bacterial suspension is introduced by pipetting 500 microliters of the suspension into each of the test tubes containing the different concentrations of chloramphenicol, ensuring that each tube has the same volume of bacteria.

What is the incubation condition for the test samples?

The test samples are incubated at 30°C for 18-24 hours to allow bacterial growth and to observe the effects of the chloramphenicol solution on the bacteria.

What do clear solutions indicate after incubation?

Clear solutions indicate that the concentration of chloramphenicol in that test tube has effectively inhibited bacterial growth, representing the minimum inhibitory concentration (MIC).

How is the minimum bactericidal concentration (MBC) determined in the experiment?

The minimum bactericidal concentration (MBC) is determined by streaking the inoculated solutions onto agar plates and observing whether any bacterial growth occurs, indicating the concentration that killed the bacteria.

What challenges are mentioned in the script regarding the experimental results?

The script mentions that experimental results may not always align with the initial hypothesis, as the test might show unexpected results, such as bacterial growth in what was expected to be an inhibitory solution.