Pic Level 191:  Drop the first bomb and then work diagonally up the inside of the black bubbles using your rainbow bubbles if needed.  This will stop the virus from touching  black bubbles. If you cannot drop the second bomb just patch it with different colored bubble to stop it ticking. Next work on dropping the sides and black bubbles.

Pic 191b:  Work around the virus and shadow bubbles now to clear your way to drop the ceiling, try to get green spiders before it comes down to boost your points.  Tip:  Hitting shadow bubbles with rainbow will prevent bubbles from emptying from cauldron.  Also If you use 3 holes in ceiling potion the virus bubble is sometimes eliminated .