Doctors tend to err on the side of caution and prescribe antibiotics whenever a cold or sore throat manifests itself. In my husband's case, they tried to overmedicate him everytime he sneezed because of his history. He contacted endocarditis as a result of extensive dental work, even though he was medicated. The infection was not diagnosed for 3 months. As a result, he was hospitalized for two weeks and on IV home therapy for three more weeks. Some months later, he had to have his mitral valve replaced. Over the past 12 years, he's been on most of the antibiotics you can imagine and had difficulty with some. He also has other health problems.
Now that he is being followed by a new internist, he does not take antibiotics for minor sore throat or symptoms of a cold. However, they do test for strep with sore throat....done that three times and all three were negative. There can be terrible, life threatening interactions with some of the potent antibiotics, such as Z-max and Levaguin. Amoxicillin seems to work well for him without huge INR swings, but the INR still does go up nonetheless because all antibiotics attack bacteria in the intestines.
There are three kinds of Vitamin K. There's the K that you get from veggies, especially the green ones; there's synthetic K, the kind they give you in the hospital if the INR must be lowered for emergency procedures; and there's the K that is manufactured in your gut from the bacteria found in your GI tract. When you take antibiotics, they wipe out the harmful bacteria and the "friendly" bacteria in the intestines that is needed for the production of vitamin K. Less vitamin K translates to a higher INR. I quess you could conclude that the more potent the antibiotic, the more "friendly" bacteria gets eliminated. It's rather like using a sledge hammer to pound in a thumb tack.
Wouldn't it be nice if one size really did fit all? This is my totally NOT-expert opinion.