<prompt> Investigation of choice of diphtheria carrier is:-Throat Swab CultureGrams stainAlbe stainZeihl Neelsen stain  <response>: Investigation of choice of diphtheria carrier is throat swab. Carriers are detected by cultural methods - swabs are taken from nose and throat and it is examined by culture methods for diphtheria bacilli. Source of infection: Carriers 95 are more common source of infection than cases 5. Types of Carriers: Temporary persists for a month Chronic persists for a year Nasal carriers are more dangerous due to frequent shedding than throat carriers. Option 2, 3: Gram Stain and Albe stain aids in identification of C. diphtheriae but not the Investigation of choice of diphtheria carrier. Option 4: Zeihl Neelsen stain: for Mycobacterium species. 