Hi again,
I didn't know a thing about lichen sclerosus but thanks to you (sorry!) I have read something and oh boy! another postmenopausal joy?!!
Have you ever used cortisone to treat it? Sometimes it can be one of the ingredients of creams, emolients. If so maybe your immune response has decreased (locally) and that could have opened the way for the Streptococcus to reproduce.
Anyway, as Taz2 pointed out, your partner has to be treated as well. I'm assuming that the swab test has detected Strep A and not B, is that right?
Another article (more recent)
http://www.ijidonline.com/article/S1201-9712(14)01611-7/fulltextIn the Discussion you can see that in absence of HRT and low oestrogen levels postmenopausal women are more susceptible to have recurrent Strep A infections, so MAYBE your lichen sclerosus is actually a complication from vaginal atrophy and if so you could use local oestrogens rather than other types of cream, emolients?