Why doesn't stomach acid kill E. Coli and Salmonella?

E. coli (like Shigella which causes bacterial dysentry) are acid resistant, so no problem, Salmonella depends on being ingested while on foodstuff, preferably containing a lot of protein, so are transmitted as food poisoning. read more

No it doesn't kill them all. Some bacteria are more resistant to changes pH than others, some have ion pumps for dealing with changes in pH, others can form spore coats very resistant to changes in pH, others still can make toxins that survive the trip through the stomach (S. aureus for example). read more

stomach. An egg with Salmonella in it could easily harbor a million times a million organisms. By cooking (but not through) you may have reduced that to 100,000 organisms. The stomach may kill 99%, still leaving 1000 organisms. That is sufficient for an enteritis. It all depends on the infectious dose of a particular organism. read more

first of all, you should know that the acidity of the stomach is not constant. A full stomach, just after a big meal, finished with a huge glass of milk may be hardly acidic, and is nothing compared to an empty, hungry stomach, ready for food. So bacteria 'sneek in' with the food. read more