It's quite difficult to find anything on this (I've tried before), as most stability studies tend to focus on stability in physiological salt conc or dextrose solutions which are used for antibiotic administration, rather than trying a range of salt concentrations per se.
I work on bacterial response to antibiotics in environments with high salt concentrations. Most of the articles in this field focus on the influence of high salt concentrations on the bacterial response to antibiotics, on the bacteria physiology and it feels to me like the influence of high salt concentrations or the antibiotic stability itself doesn't get enough attention.