Coliform test sensitivity

[SKA]

Is this test more sensitive when it comes to detecting bacteria compared to the Resazurin and Methylene blue reduction tests?

[theprof]

Err in view of our discussion last night, I think you'd better rephrase this question as it doesn't make a lot of sense.

You cannot directly compare the two. Furthermore you're not making it clear if you're talking about coliforms or bacteria in general.

[SKA]

We did a practical on raw and pasteurised milk doing s
Methylene blue reduction test
Resazurin
Coliform test and
an aerobic plate count

the results for the first two tests were similar so they were expected but the coliform test had bubbles in the pasteurised milk and the plate count for it was quite high. So I was thinking is the coliform test more sensitive then the first two tests but I don't understand the high plate count either!!

[theprof]

OK. The high plate count is undoubtedly due to the presence of other anaerobes. I'm assuming you weren't given the opportunity to identify them.

Sensitivity doesn't really come into it as both EMB Agar and nutrient broth will grow other anaerobes in the right circumstances. This sort of thing can also happen if you try to take shortcuts in the coliform test techniques.

[SKA]

I don't understand why the pasteurised milk which passed the methylene blue test and resazurin had bubbles in the coliform tube and a high amount of colonies on the aerobic plate?

[SKA]

could it mean that the pasteurised milk wasn't pasteurised properly or was about to go off?

[theprof]

You've beaten me to it. That's exactly what I was about to suggest. The most likely scenario is that the milk was about to go off.

[SKA]

aww thank you so much for all your help don't know what I'd do without you!!