Clean machines

Joseph Webster J.Webster at
Mon Feb 24 18:38:31 EST 1997

At 11:44 AM 24/02/97 +0000, Arnold Pizzey wrote:
>        I would question the efficacy of using 70% ETOH alone as a
>sterilization agent specifically in flow as well as generally in the
>laboratory. Although ETOH has some bactericidal activity against common
>water-borne contaminants such as the pseudomonads and the like I would
>imagine that most airborne contaminants that float into the sheath tank
>would be of the Gram-positive persuasion and as such quite resistant to the
>effect of ETOH.

This is a very useful & timely warning for people like me with
mechanical/engineering background rather than lab/biology trained.
I've always been led to believe that 70% ETOH will knock off anything
of interest in this context.
Anyone else (microbiology types?) like to comment?

>	As for swabbing down external surfaces with 70% ETOH, I would
> regard this as an excellent strategy for mobilizing bacterial aerosol.

Could you please expand on this Arnold?
Maybe we're not talking the same language; To me, "swabbing down"
means "take some material (paper towel, tissue etc), douse it with
some solvent (70% ETOH) and wipe the area or object to be cleaned
with the solvent-wet material."

This to me specifically excludes splashing or spraying, and I'm
not able to equate this activity with creating or mobilising
any aerosol.

>On the few occasions when I have had to carry out sterile sorting, my
>strategy is as follows:
>	Clean sort nozzle/flow cell /sheath tank with a proprietary detergent and
>rinse in sterile H2O.
>	Wash the sort collection area down with a proprietary detergent
>	Bypass the in-line sheath filter, Then flush system with following:
>	1)H2O
>	2)Surface active agent e.g. 0.1% DECON 90
>	3)Sterile H20
>	4)Sterile sheath fluid
>	5)Fit new sterile in-line sheath filter.

Maybe I'm missing something (as I often do!) but you have not
included anything that I recognise as a sterilising agent.
Which of these steps is intended to kill pre-existing bugs?

Many thanks for your tolerance of my ignorance, this old dog
would like to learn some new tricks.

	Regards, Joseph.

Joseph Webster
Flow Cytometry Facility
Centenary Institute

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