What Causes Sore Throat?

Question : HI, Recently I attended a conference with 5500 people from 7 different countries. It was 4 days, 13 hours a day in a cold environment. A lot of high 5ing, hugging, and general close quarters with a lot of people. Factor in that I also was drinking a lot, and not getting much sleep. I flew home, with a very mild sore throat, which I attributed to a lot of yelling we were doing at the conference. It should be noted that my tonsils, normally are +4, and have been for most of my life. After about 4 days, I woke up with a fever, 102, and a terrible sore throat, and sinus pressure. No cough or sneeze, just some post nasal drip. I went to the ER, and they gave me a rapid test, which came back and said Moderate growth of Normal throat flora isolated. What does that mean? They gave me penicillin, and sent me home, but after 24 hours, I felt a little better, but still didn't feel 100%, the ER Doc said it was an upper respiratory infection. I went to my primary who said that I needed IV antibiotics and that I needed to be admitted to the hospital, which I was. The IV antibiotics worked like a charm! They diagnosed me with Accute Tonsillitis, gave me a 10 day script for Agumentin, and Medryldosepack and I have been fine since, actually had my tonsils out. I'm trying to figure out how it was Bacterial (since antibiotics worked) with the results of that rapid strep test I got in the er. Please help.

Thank you for your prompt response! So then Moderate growth of Normal throat flora isolated, DOES in fact indicate strep throat is what you are saying? The Doctor in the ER kept trying to test for Viris, which is what threw me off as I Know antibiotics don't work in Viral infections. And also, I didn't have any spots or pus on the tonsils at all.