Staph aureus

I had a doe that had bitter tasting milk. I had it cultured & it came back no growth. Then she started having some blisters on her teats. One came to a head & it had some pus. She started getting more of these and some felt more internal than external. Eventually she got mastitis and that culture revealed Staph A. 2 of my other does now have one or 2 similar blisters. At the first sign for all of them I began washing the affected areas with chlorhexidine. I'm not really milking any of them. The first one wouldn't let her kids nurse normally so I would put her on the milk stand and let her kids nurse her empty that way. The other 2 are first fresheners and their kids are able to keep them milked out. So basically I am wondering what to do to prevent the 2nd two from getting mastitis and if there is a way to prevent these blisters in the first place. My 4 other milking does have not had this issue and I'm just not sure what to do. Thanks!