wow wow people, its dangerous to do a diagnosis bases on history alone on what he says. As he said he already did a swab, took a course of antibiotics and had a 2nd opinion at another clinic, where they told him he is recovering.
Further more he is apparently stressed. Personally I would tell him to chill out, if they did a swab at the clinic, mean they know exactly what he got and gave him the medication accordingly. I would say that the redness remaining is some slight inflammation remnant after the infection.
What i would suggest is to take some vitamins to boost up your immune system vit C tablet [and or oranges or other fruit rich in vic c] and vit D, which you can get from cod liver oil capsule, and if you want something rich in antioxidant like green tea. That's all.
If really you dont feel well after a couple of week more just visit your doctor do another swab and, take your medication accordingly, because sometimes after an infection, due to the fact that your immune system taking a hit, you can develop a secondary infection.
But remember its dangerous to just ask him to take any drugs based on history alone.