What is the primary purpose of performing a Most Probable Number (MPN) test on a food or water sample?

Question

BlackTom AI · Accepted Answer

MPN estimates the concentration of viable (culturable) bacteria in a sample when conventional plate counts cannot be used easily or reliably.

Relevant knowledge points and concepts:
- MPN (Most Probable Number) is a statistical, culture‑based method that uses serial dilutions and replicate liquid media tubes or wells to detect presence/absence of growth at each dilution.
- It yields an estimated concentration of viable organisms (not viruses, dissolved solids, or an exact spore count) with confidence limits, based on probability theory (binomial/Poisson) and lookup tables or maximum‑likelihood calculations.
- MPN is suited for samples that are turbid, particulate, contain clumping organisms, have low organism density, or where plating is impractical.

Step‑by‑step reasoning process:
1. Prepare serial dilutions of the sample (for example 10^0, 10^-1, 10^-2) and inoculate several replicate tubes/wells at each dilution.
2. Incubate under appropriate conditions and record which tubes show growth (positive) versus no growth (negative).
3. Count the number of positive tubes at each dilution and form a pattern (e.g., 3–1–0 positives at successive dilutions).
4. Use an MPN table or an MPN calculator (maximum‑likelihood estimation) to convert the pattern of positives into an MPN estimate expressed as viable organisms per unit volume, often with confidence intervals.
5. Interpret result as an estimate, not a precise colony count; MPN relies on the probability that an inoculated aliquot contained at least one viable organism.

Why the correct answer is correct:
MPN directly estimates viable bacterial concentration by detecting growth in liquid media across dilutions; it is specifically designed for situations where plate counts are impractical or unreliable.

Why the other options are incorrect:
- Detect virus particles: viruses require cell culture, molecular assays (PCR), or plaque assays, not standard bacterial MPN.
- Determine total dissolved solids: this is a physicochemical measurement (gravimetric) unrelated to microbial culture.
- Count fungal spores precisely: fungal spore counts typically use microscopy, spore traps, or plating; MPN gives statistical estimates for culturable organisms and is not a precise spore‑count method.

Conclusion: The primary purpose of MPN is to estimate viable bacterial concentration when plate counts are impractical, which matches the provided answer.

What is the primary purpose of performing a Most Probable Number (MPN) test on a food or water sample? 多项选择题

类似问题

6. What are the general characteristics of most probable number (MPN)?

Which of the following statements is False regarding the post-closing trial balance?

A closing entry may include a Blank ______.

Earnings per share is reported at the Blank ______ of the income statement.

Table 3 shows the short-run production costs for a car wash: [table] Costs | Cost per month ($) Land lease | 4,000 Workers’ wages | 2,600 Car wash machines | 3,000 Water | 1,500 Cleaning chemicals | 900 [/table] In the short run, calculate the car wash's fixed costs in Table 3.

During the closing process, the closing entry to reduce the sales revenue normal account balance to requires the revenue account be debited.

As of December 31, $2,500 of interest expense has accrued on a $50,000 note payable. The note payable and the accrued interest will become due and payable next year. How will the interest affect the adjustments at the end of the period?

Positive economic profit is the same as?

更多留学生实用工具

智能学习助手

风格化写作助手

论文查重助手

文献引用助手

课堂转译助手

课堂笔记助手

Quiz搜索助手

学校历年真题

智能刷题助手

智能匹配练习

希望你的学习变得更简单