Well, you need that gelatin material as well, which you should have. I'd scrape the bathroom with some type of device - be sure to have gloves on....First, scrape the phone EVERYBODY uses. Then, scrape the bathrooms - and I mean good. Sinks, soap dispensers, etc. The floor is a good place where a lot of bacteria hang out, and anything that is rubber or squishy....stairwell railing is a good place as well. Doornobs, etc. Scrape all these things with different q-tips or wooden sticks, and then rub it on the gelatin at the bottom of the petri dish. It'll work.