How long does bacteria live outside for? In summer, on plants or grass or patio,eg:salmonella or feaces?

I've got cat poo on my lawn and patio which I picked up the bulk but there's still marks and a bit of cacky stuff where it remains in the grass/mud and a smudge Mark on patio slab! How can I make it safe enough for my toddler to go out and play ? Thanks x