bacterial infection
"I love this stuff! I am a smoker so am prone to getting bronchitis more.  Getting sick stinks but when i get bronchitis which is almost every year i get this med and by the 2nd or 3rd day am feeling much better and by day 4 I don't really feel like am sick anymore but you need to finish the meds! That is the must.  A have also been told that it might not work the first time around so you need to take a 2nd round of the meds. I call it the miracle drug!"