Hi Madam A Dtor:
A pH of <3.2 with sufficient quarantine time (temp controlled) is a kill step. You see it all the time in sauces and mayonnaise where folks don't want to use heat as a kill step. I've attached a couple of studies for you to review.
Not my area of expertise but for the general case, it's possibly not quite so simple as quoting a pH, eg -
(A Regulatory CCP/PRP ?)
(Microorganisms in Foods,Vol5,2005) (the current validity of above/EC comment [if applied in UK] needs to be checked)
Personally I prefer to avoid the word "kill" but it certainly appears there is agreement that various pathogens when added to specified mayonnaises do not "survive". eg -
Salmonella, E. coli O157:H7, E. coli, L. monocytogenes, Staphylococcus aureus, and Yersinia enterocolitica die when inoculated into mayonnaise and dressings.
It's also unfortunately true that "does not grow" cannot automatically be equated to "does not survive", eg the US peanut disaster.
PS - if interested to see a variety of, apparently, common (mis?)conceptions can try this -