Bacteriological culture for diphtheria is performed for the purpose of laboratory diagnosis of diphtheria infection, identification of the source of infection and confirmation of epidemiological links. Culture is performed when diphtheria is suspected, for which swabs are necessarily taken from the throat and nose.

The causative agent of diphtheria is the bacterium Corynebacterium diphtheriae (Leffler's bacilli). These are gram-positive bacteria that are capable of producing diphtheria toxin.

Diphtheria is transmitted by airborne droplets. The source of infection is sick people or carriers of the bacteria.