Staphylococci
If I remember my Latin, Staphylococci is a very broad term for the entire range of Staph infections. I'm not a vet, but here's what I do know about staph infections in general - and this is just from my own rescue dog's experience.
Staph infections are bacterial in nature and can be related to many common canine conditions such as puppy acne, demodectic mange, etc.
Secondary staph infections can also develop when there is excessive itching and scratching to the point where the skin surface is open, which enables the bacteria to wreak even more havoc on the animal. This was the case with our dog. He had sarcoptic mange and scratched himself raw and those damaged areas of his skin became very infected.
Staph infections can be a sign of a weakened immune system or some kind of parasitic infestation. I'd pump your vet for as much information as possible and ask for a thryroid profile. If your vet can't answer your questions then get a second opinion.
I don't know what you feed your baby, but check into adding probiotics to the diet or consider homecooking or BARF.
Staph infections are certainly treatable, so don't panic. Hang in there .
I hope this helps!
melissa & beasley