Shaph overgrowth is usually due to an underlying allergy, most of often food. There are individuals that are also sensitive to the microbe itself, but this is very rare. If treating for staph infections, please do so under the advisory of a Vet with a culture and sensitivity test. If treating empirically, you can create a larger more dangerous problem like MRSA. This is not something to mess around with. Some common antibiotics actually increase the instance of mutation in some microbes; if you don't know for sure what you are doing, you can exasperate the problem. I just saw such a case with a UTI. Now the E Coli infecting is resistant to almost everything, due to empirical antibiotic use.