Nasal swabbing using agar culture identified two-thirds of the total MRSA carriers who were diagnosed by multiple body site screening using agar plus nutrient broth culture. Nasal swab screening combined with culture on agar is a commonly applied method for detecting MRSA carriage.asal swabbing using agar culture identified two-thirds of the total MRSA carriers who were diagnosed by multiple body site screening using agar plus nutrient broth culture. Nasal swab screening combined with culture on agar is a commonly applied method for detecting MRSA carriage.