Q: I took my 6-year-old to the doctor because she had a sore throat with white patches — strep, I assumed. So I figured the doctor would take one look at her and prescribe an antibiotic. But he took two throat swabs, did an office strep test on one — which he said was negative — and sent the other sample to a lab. When those results came back, it turned out it was strep after all. Then the doc gave her amoxicillin. But I wonder, is this doctor incompetent?

MURPHY A., NEW CITY, N.Y.

A: Actually, quite the opposite. Your doctor was following the latest guidelines recommended by the American Academy of Pediatrics and the Infectious Diseases Society of America. The last thing your daughter needed was an antibiotic to treat tonsillitis caused by a virus. (Antibiotics are designed to knock out bacteria, but are 100 percent useless against viral infections.) The Rapid Antigen Detection Test (or RADT, which he did in his office) is usually pretty good, but it’s not 100 percent accurate. So your doctor was smart to go with the gold standard and have a lab determine if your daughter had a bacterial infection or not.

Because of the increase of antibiotic-resistant bacteria, it’s getting more and more important for doctors to prescribe antibiotics only when they’re called for. Doctors who follow the same guidelines as your doctor cut their erroneous antibiotic prescription rate in half — from 28 percent to 14 percent. Antibiotic-resistant bacteria are becoming a bigger health problem every day, and your doctor was doing a very good job of dispensing the proper antibiotic at the right time. Penicillin has saved a lot of lives, and if it’s overused it could someday lose its effectiveness.

The You Docs — Mehmet Oz, host of “The Dr. Oz Show” and Mike Roizen of Cleveland Clinic — are authors of “YOU: Losing Weight.” To submit questions, go to www.RealAge.com. A King Features syndicate.