Salmonella is everywhere in nature.  It is in my body and your body.  Likely in our hair, on our skin, everywhere.
The danger is when an environment is right for it to multiply and breed voraciously, such as in meats and foods.  It is real.
That said, exercise normal precautions and safe practices of hand washing, of course.  
Chicken litter/manure is a fabulous material used our production gardens. I could not garden without it.  Our soil is far too poor without it.  It far surpasses chemical fertilizers in quality.  Again, follow the guidelines of manure application and/or composting.  Chicken poop is pure gold.