4 replies to this topic

[mmcgill]

Here is the deal: I changed the medium on some cells recently. When I checked them under the microscope immediately after, there were a couple of thick stringy floating "fibers." Not a lot, just a few fibers in a couple of wells. No cloudiness, no other obvious signs of contamination, and the cells looked very healthy.

Here is the puzzling thing: I had JUST filtered the added medium through a 0.22 um syringe filter before putting it on the cells. I'm a guy with hairy arms and I had my sleeves rolled up in the culture hood to avoid dipping in the medium, so I'm wondering if it could be very very small hairs from my arms? Or maybe fibers from the filter?

Any opinions or similar experiences?

Thanks.

[bob1]

If you could provide pictures, that would be a help.

Occasionally you will find plastic fibers or precipitates from FBS in your medium.  The FBS ones don't look much like hairs though, more like crumpled up sheets of plastic.

If the fibers don't proliferate, then they aren't fungus.

Ideally you would be using a lab coat with which you could use gloves to cover the openings of the sleeves (similar to how a surgeon gloves up) - this helps prevent contaminations/worries of this sort

Edited by bob1, 18 October 2011 - 05:28 PM.

[hobglobin]

From the description I also would say it is a lint or fluff, i.e. some sort of fiber. The hair cuticle usually has a distinctive structure, i.e. the surface looks like made of scales. But you need to use a microscope to see it.
The diameter of hair is around 10 µm to 100 µm...so most hair would be too large.

[mmcgill]

Thanks for the suggestions.

You are right that hair would have a distinct appearance, so that is not likely to be it. Also, I can only see these fibers with a microscope - they are not visible to the naked eye. Initially, I just thought that it could be very very fine hairs, but I can't see anything that looks like a root.

I also can't make out any discernable growth. If these fibers do grow (like a fungus) then it is so slow as to be imperceptible over the course of a couple of days.

Another possibility I've considered is that these are fibers coming loose from my sterile filters (I sterile filter the medium immediately before putting it on the cells). I suppose that could be it.

Any additional suggestions/thoughts?

Thanks.

[mmcgill]

Thanks for suggestions.

It turns out that it probably is a fungus. The growth has been very slow, but today I checked a few wells and it seems as though more has sprung up overnight. Macroscopically, there are transparent film-like growths in the medium. Under the microscope, these growths look like networks of fibers. I'm pretty certain it is fungal contamination.

I'm planning to disassemble the incubator, autoclave the shelves, and wash the walls with bleach and then EtOH. I'll also wipe down my hood the same way and probably autoclave the working surface of the hood.

Thanks again.