What is the difference?
Ong Peik Looi
I'd like to know the difference between MPN, CFU & PFU/100ml in the tests for fecal coliform and coliform. From the likes of it, I don't think that they are from similar test methods. Can I compare them numerically? Is there an equation to convert either one of them to the other? Right now, I have one sample in MPN/100ml and the other in CFU/100ml. What is my basis for comparison?
Would appreciate any information or references. I'd like to thank you in advance for your response.
David L. Rosen
>
> I'd like to know the difference between MPN, CFU & PFU/100ml in the
> tests for fecal coliform and coliform.
CFU is Colony Forming Units." The colony appears as
spots. Usually, each colony represents a founder. This is
usually applied to bacteria.
PFU is "Plaque Forming Units." A colony of orginisms
appears as a hole in a colony of cells. The microorganism is
killing some other form of life, leaving a hole. Each hole
represents a founder. This is usually applied to viruses.
Viruses are so small, that even a colony of viruses can never
be visible to the naked eye. The damage a colony does, however,
the "plaque," can be monitored visually.
Mike Steven
In article <586961E274B1D111883308002BA60B6697445C@MAIL8>, Ong Peik Looi
<CPL...@ntu.edu.sg> wrote:
> I'd like to know the difference between MPN, CFU & PFU/100ml in the
> tests for fecal coliform and coliform.
MPN (most probable number) uses the multiple tube fermentation method and
is based on a statistical estimation - you need to calculate 95%
confidence limits for this result as it is only an estimate.
CFU/100mL is colony-forming units - thus the count of bacterial colonies
produced on agar plates. if you did duplicates you can also calculate 95%
conf. limits for this. As the media used is different the results will
not be comparable. However if both media aimed to isolate the same
species eg E. coli the cls should overlap.
PFU/100mL is plaque-forming units thus counting bacteriophage and totally
non-comparable with the first two. However they are used as "indicators"
of water quality and in this regard should vaguely relate to the others if
natural water is being tested (as opposed to a lab-made sample used for
instructional purposes)
Hope this helps
Vicki
Francois
MPN/100ml is a statistical probability of the number of organisms per 100ml.
CFU/100ml is an actual count from the surface of a plate, like in total
plate counts.
As reference try and find: Standard Methods for the Examination of Water and
Waste Water.
Edited by Andrew D. Eateon et al. Publication Office: American Public
Health Association.
Check out the chapter on Microbiological Examination.
It describes the different methods for examination of faecal coli's and
coliforms by the MPN technique and the membrane filter count procedure. It
explains the interpretation of the counts for both as well.
Hope that helps
Francois
Ong Peik Looi wrote in message
<586961E274B1D111883308002BA60B6697445C@MAIL8>...
I'd like to know the difference between MPN, CFU & PFU/100ml in the
Ong Peik Looi
I wish to thank all of you for your prompt reply and information. I wanted to have an expert opinion about these two tests.
Has anyone performed a comparison between these two counting methods? What is the order of magnitude difference between MPN and CFU for the same sample? Also do you have any references or information of any kind, where the sampling of fecal coliform were performed in tropical waters ( where temperatures are almost constant throughout the year; varying within a range of say, 28 to 32 deg. C) at different depths. I came across a paper by Evison and James comparing E.Coli in the waters of UK and South Africa in 1973. Not much luck after that.
I would really appreciate it if you can put me through somebody who is researching or an expert in tropical waters. Would like to get an idea of the range of die-off rate for fecal coliform & E.Coli.
fieldb...@gmail.com
simone.giac...@gmail.com
> Hello! I've read your answer about the CFU and MPN. I would like to ask if it's possible to convert MPN to CFU and if it's possible, what is the formula? I really appreciate the answer you're giong to give me. Thank you so much.
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.220.2828&rep=rep1&type=pdf