First, consider all of the information above. If you still want to culture this bottle and don't have a few bottles, do the following:
- Bring a stock pot of water to a boil and sterilize a propagation vessel (mason jar, glass peanut butter jar, 12 oz beer bottle, etc.)
- In a pot, mix a 10% malt extract solution (500 ml water, 50g light dme)
- Boil for 15 minutes
- Cover, cool and transfer to sterilized propagation vessel
- Swirl up the dregs of the bottle you wish to culture
- Pour the dregs into the vessel
- Either place foil over the top or an airlock with appropriate stopper or a loose fitting lid
Wait 2-3 days and you should see some sediment with a definitive layer of yeast. From there, you just need to either step up to a pitchable amount by feeding with more wort to the desired volume, or by transferring to your preferred yeast storage method (washing, slanting, freezing).
Hope this helps.