MicrobeHunter.com Microscopy Forum

high school teacher here....new microbio course....with all these gram stain slides i have....do i have to autoclave and toss them all in trash?
If i soak in soap will the heat set bacteria come off enough that i can autoclave and reuse them? I hate to waste them! thank you!

I would clean and reuse them. Why would you autoclave them?

Peter.

I'd leave them in bleach for a couple of days.

Of course you can reuse the slides. We tossed them into Hazardous Waste in the hospital lab, but that was because of the glass, not the organisms. In a hospital it is rarely cost effective to wash things like slides. Labor costs too much, particularly when you're doing 50-100 gram stains a day. School budgets being what they are, washing and reusing slides makes perfect sense.

No need to autoclave - though you can if you want - it won't hurt the slides. The gram stain process should kill everything, but if you're worried, soak them in 5% household bleach for a couple of hours, then wash them in dish detergent or Alconox.

Tom

For high school, I would say use a mix of vinegar and original formula dawn dish detergent. When I ran a microbiology and mycology lab, we would put slides in a 2 liter container with the vinegar/dawn mix and let it sit until full. We then cleaned them all and let them dry. The stronger the acetic acid the better, so if you can find the 20% vinegar that is sometimes sold in grocery stores that would be good. Vinegar removes a lot of stains used in a microbiology lab. Though, usually you need the concentration to be above 50% to quickly clean stains.

MNMyco

For the final cleaning of slides a dish washer is useful: You take the plastic inlet of a 50 or 100 slide box and drill big holes in the bottom with a hole cutter. Depending on your dish washer and the type of plastics you may have to remove it before the final drying step. For some preparation techniques like blood smears the surface of the slide is important. This can often be optimized by drawing the slide through the flame of an alcohol burner.

Bob