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Incubator contamination - red swipe from incubator interior (Sep/04/2008 )


I think there's some kind of contamination in my incubator (fan-assisted, 5% CO2, 3%O2, water added to the bottom reservoir). The cells I'm growing (HEK293) appear ok. There's no turbidity and no change of phenol red color in the cell culture media. But sometimes there's excessive debris in my culture plates. Some appear like large fiber, some appear like tiny black speckles. They don't seem to swim around and they don't seem to replicate either (or their replication is very very slow). I did DAPI stain, and my cells seem clean.

But when I was cleaning my incubator, some fungus-like growth can be clearly seen on metal trays around the edge of the holes. When I was wiping the interior walls with 70% ethanol, I noticed red stain on my wiping tissue paper.

Can someone tell me what kind of contamination this could be. I'm very interested in finding out the name/species of this contaminant, because it might have changed my experimental result in a very interesting way. I am suspecting that this growth of contaminant in my incubator could have increased oxidative stress in my cell culture. Perhaps toxin or gas released by the contaminant caused this phenomenon in my experiment.

Please help, thanks a lot in advance.



In relation of cleaning you incubator always use 70% alcohol and 10% bleach and change your water at least twice a month to ensure a complete decontamination. In relation to the identification of the culprit I suggest that you take an agar plate or broth and take a sample. Then locate a mycology dept, near you and have them help you with the identification.
Sometimes when you are working with cultures such as yours, everything in the air (from the transportation to opening the cells in the hood, from opening a new box of tips nearby) can get into your flask. A way of controling this is to set up everything before you bring your cells into the hood and UV it (exept the medium of course), and also, be sure there's not many people around (I was once working with a cell line and someone in the room sneezed and there went my cells; they got completely comtaminated even though I was in biohood).
Remember, when you are handling cultures you can never be over-meticulous in your cleaning and handling

Good Luck!!!