Can salmonella contaminate your garbage disposal?

Yes. The drain, and plug of kitchen sink can get quite funky. Studies confirm high bacterial counts (comparable to a toilet) no reason to think disposal any "cleaner". Disinfect: run cold water for several minutes; pour 1- 2 cups of chlorine bleach into drain, let sit for 10m, hot water for 2m; disposal?: turn it on during flush. 2x/wk. Clean out debris daily; plug in dishwasher; liquid soap.
Suppose it's possibl. Salmonella enterica can be found in poultry & produce (like lettuce leaves) or so the CDC says. If u have an in-sink garbage disposal, I suppose small bits of food containing Salmonella could act as a contamination reservoir. However, any food in contact w/ the garbage disposal should not be eaten; wash your hands with soap & water if you touch the disposal & before eating to prevent transmission.