I'm in the medical field with a patient load of over 350 patients each day and YES...we don't prescribe anti biotics until we get a positive test. Nowadays we do in house strep and mono tests that take 5 minutes. We get cultures back in 24 hours. We will call in the script ONLY with a positive culture.
In case you have not been reading the papers lately, MRSA staph super bugs are spreading here exactly because broad spectrum meds are dispensed before a correct diagnosis is made. And IF broad spectrum meds are given and taken, then a blood test culture test 24-48 hours later is now void and not valid.