Hi Kate
What sort of reading would you expect to get at 600nm for a 1:10 dilution?
I think what everyone is wondering is a fail safe method because of the timing issues, when you have the  final  growth on the plate your test may be not valid and you have to go throught the excercise again starting from the begining of growing your Aspergillus from scatch.
In one person lab when you need to be as efficient as possible there is a very little time for erorrs.
I grow my cultures on 2 SD slopes and use a 5mls of diluent to harvest it. My McFarland reader has a scale up to 5 and when it gets past it I use the suspension. I will try the 1;10 dilution to check if this may be more accurate estimate.
Kind regards
Agnieszka
 
-----Original Message-----
From: The Pharmaceutical Microbiology Forum Email List [mailto:[log in to unmask]] On Behalf Of Kate Ambrus
Sent: Thursday, 12 May 2011 5:37 a.m.
To: [log in to unmask]
Subject: Re: [PMFLIST] Aspergillus spore suspension

We used to use 600 nm. There were some discussion earlier where people use about 450 nm, but you can establish a workable absorbance range at whatever wavelenght works for you. Just remember that the spec reading is an estimate only - you still need to do a plate count method to establish the actual counts every time you use your suspension. And you need to read the 1:10 dilution of the suspension, otherwise it is too black to be read.
 
Good luck,
 
Kate Ambrus

--- On Wed, 5/11/11, alessandra garces <[log in to unmask]> wrote:


From: alessandra garces <[log in to unmask]>
Subject: Re: [PMFLIST] Aspergillus spore suspension
To: [log in to unmask]
Date: Wednesday, May 11, 2011, 5:39 AM


Hello Kate, Wicht is the wavelength that you use in your spectrophotometre
for fungus???
regards, aless


2011/4/30 Kate Ambrus <[log in to unmask]>

> Acording to USP/EP Guidelines. Grow for 7 days at 20-25C on Sabouraud
> Dextrose plate (we used to use a large 150 mm plate to get more spores),
> harvest with sterile saline solution containint 0.05% TWEEN 80 - scraping
> the surface of the growth with a sterile spreader  - all done in a hood,
> filter through a cell strainer set in a funnel (containing an additional
> layer of sterile gauze) - twice, and refrigerate in a test tube at 2-8C for
> up to 7 days. We used to check the suspension under a microscope to make
> sure there was no to little mycelium or spore heads present.
>
> In addition you can establish spectrophotometric readings that will assure
> that your suspension is in the 10E8 range - recommend diluting 1:10 before
> reading on spectophotometer - make sure to then use the original suspension
> and not the 1:10 for inoculation of samples.
>
> I hope these guidelines have not changed since 2009 when I retired.
>
> Kate Ambrus
>
> --- On Thu, 4/28/11, chaitu satyada ` <[log in to unmask]> wrote:
>
>
> From: chaitu satyada ` <[log in to unmask]>
> Subject: [PMFLIST] Aspergillus spore suspension
> To: [log in to unmask]
> Date: Thursday, April 28, 2011, 10:57 AM
>
>
> Hi
>
> can any one tell me how they are preparing  *Aspergillus* spore suspension
> for preservative efficacy test
>
>
> with regards.
> sk
>
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>
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