Corynebacterium ulcerans (toxigenic C. ulcerans) produces the diphtheria toxin, 
which causes pharyngeal and cutaneous diphtheria-like disease in people, and 
this bacterium is commonly detected in dogs and cats that are reared at home. It 
is considered dangerous when a carrier animal becomes the source of infection in 
people. To investigate the carrier situation of toxigenic C. ulcerans of cats 
bred in Japan, bacteria were isolated from 37 cats with a primary complaint of 
rhinitis in 16 veterinary hospitals in Osaka. Toxigenic C. ulcerans was detected 
in two of the cats. By drug sensitivity testing, the detected bacterium was 
sensitive to all investigated drugs, except clindamycin. It appears necessary to 
create awareness regarding toxigenic C. ulcerans infection in pet owners because 
this bacterium is believed to be the causative organism for rhinitis in cats.