PEMBACAAN DAN PERHITUNGAN KOLONI UNTUK UJI ALT BAKTERI AEROB

Summary

This video script outlines the procedures for counting bacterial colonies in microbiology, detailing the types of colonies, counting rules, and special cases such as the 'PBUD' (too numerous to count). It covers the necessary steps for colony counting from agar plates, including dilution methods and adjustments for control plates. The script emphasizes the importance of accurate counting, calculation formulas, and reporting results in standardized units. It also provides guidelines for rounding and handling specific cases, ensuring reliable and reproducible results in laboratory experiments.

Takeaways

• 😀 Colony types are classified into three categories: chain, breaded, and rider. Each has distinct characteristics and should be counted as individual colonies based on their appearance and spread.
• 😀 Colonies in the range of 25-250 per petri dish are valid for counting. If a petri dish exceeds 250 colonies, it is labeled as 'PBUD' (too many to count).
• 😀 If a petri dish has too many colonies (>250), the colonies can be counted by multiplying one side of the petri dish and applying the appropriate factor, such as multiplying by four.
• 😀 If a petri dish has fewer than 25 colonies, it is treated as 'less than 25' and multiplied by the dilution factor to get the final count.
• 😀 Colony counts from control dishes (e.g., BFB, BCA) must be subtracted from the total count of experimental dishes to eliminate contamination effects.
• 😀 AELT (Adjusted Estimated Load of Total Bacteria) is calculated using the formula: n = ΣC / (1 × N1 + 0.1 × N2), where ΣC is the total valid colonies and N1, N2 are the respective counts of petri dishes.
• 😀 If all petri dishes in a dilution series show colony counts greater than 250, they are marked as 'too many to count' (PBUD).
• 😀 Results are rounded to two decimal places, with specific rounding rules based on the digit following the decimal point (e.g., rounding 2.72 to 2.7, and 2.78 to 2.8).
• 😀 For liquid samples, the colony count per milliliter is adjusted by multiplying the result by a factor of 10 to standardize it to 1 ml.
• 😀 If there is contamination in the test, such as when more than 10 colonies are present in the control, the entire test should be repeated to ensure accuracy.

Q & A

What is the general process for counting bacterial colonies on agar plates?

The process involves incubating the agar plates, counting colonies on each plate, and differentiating between small and large colonies, which are counted as one each. The total number of colonies is then calculated by summing up the counts from all the plates.

What are the three types of colony growth patterns identified in the script?

The three types of colony growth patterns are: 1) Chain colonies, where the colonies are connected, indicating bacterial clumping; 2) Breaded colonies, where the colonies grow in a layer between the agar and the dish surface; 3) Rider colonies, which grow along the sides of the plate.

How should chain colonies be counted?

If there is only one chain of colonies, it is counted as a single colony. If there are two or more chains originating from different sources, each chain is counted as a separate colony.

What should be done if the colony growth covers more than 25% of the plate surface?

If the colony growth, such as spider-like patterns, covers more than 25% of the plate surface, the test should be repeated to avoid inaccurate results.

What is the maximum number of colonies allowed on control plates before a retest is required?

The maximum number of colonies on control plates (e.g., control BFB and control BCA) should be 10. If more than 10 colonies are observed, the test must be repeated to avoid contamination during the experiment.

What is the purpose of subtracting the colony count on the control plates from the test plates?

The colony count on control plates is subtracted from the total count on test plates to eliminate the effect of background contamination, ensuring more accurate results for the test samples.

What is the range of colony counts that qualifies a plate for the CFU calculation?

Plates with a colony count between 25 and 250 colonies are considered valid for CFU calculation. Counts outside this range (either too few or too many colonies) are not included.

How do you handle plates with colony counts greater than 250?

If a plate has more than 250 colonies, it is considered 'too many to count' (PBUD) and should not be included in the CFU calculation. The final result is reported with the notation for 'PBUD'.

What method is used to calculate CFU when there are too many colonies on a plate?

In cases where colonies are too numerous to count, the plate can be divided into sections. The number of colonies on one section is counted, and the total is multiplied by the number of sections to estimate the total colony count.

What is the formula used to calculate the total CFU based on colony counts from multiple plates?

The formula to calculate CFU is: n = (ΣC) / (1 * N1 + 0.1 * N2), where ΣC is the sum of all plates with 25-250 colonies, N1 is the number of plates at the first dilution level, N2 is the number of plates at the second dilution level, and d is the dilution factor.