Answers. Best Answer: Sulfa antibiotics such as Bactrim do NOT cover for the strep infections. They do cover most bacterium that cause sinusitis, however. If you truly think you have strep throat, you should see your doctor for a throat culture and emperic starting of a penicillin, omnicef, or keflex. Source(s): harley_pa · 6 years ago. Thumbs up.