You're concerned about three A's and a B-?  No offense, but this is classic pre-allo SDN.  Take a deep breath and send the grades...not sending them is far more conspicuous, and you have NOTHING to be ashamed of!  A B- in Microbiology probably won't turn adcoms off to you, and you'll get plenty more of the subject later on.  I think you're in good shape...good luck!