Horse question? Strangles?!?!?

So I got this horse from an auction hes been here for 3 weeks now, he got antibiotics he finished last week which appeared to be a 'cold' the shipper said it could of been strangles. We were going to wait longer to keep them separated but he hopped the fence, then got with my other horse. Do you think they be ok? He doesn't have strangles for sure, but came off antibiotics 5 days ago, and showing no signs of anything. If not what should I do?