To diagnose S. aureus, a sample is obtained from the infection site and sent to a microbiology laboratory for testing. If S. aureus is found, the organism should be further tested to determine which antibiotic would be effective for treatment.
Doctors often diagnose MRSA by checking a tissue sample or nasal secretions for signs of drug-resistant bacteria. Current diagnostic procedures involve sending a sample to a lab where it is placed in a dish of nutrients that encourage bacterial growth (a culture). It takes about 48 hours for the bacteria to grow. However, newer tests that can detect staph DNA in a matter of hours are now becoming more widely available. This will help healthcare providers decide on the proper treatment regimen for a patient more quickly, after an official diagnosis has been made.
In the hospital, you might be tested for MRSA if you show signs of infection, or if you are transferred to a hospital from another healthcare setting where MRSA is known to be present. You also might be tested if you have had a previous history of MRSA.