Locus of Mammary Gland Infections of Corynebacterium bovis

Abstract

Corynebacterium boris was shed in 33.5 and 38% of aseptically drawn milk samples from two university dairy herds. Individual quarters were examined to determine locus of infection. C. boris was cultured from only 5 of 20 samples drawn by syringe from the teat cistern but was in each of the 20 samples drawn through the streak canal. Counts of C. boris averaged 23,000 from cross sections of streak canal of about 1 mm thickness. Numbers of C. boy,s were fewer in Furstenberg's rosette and none was recovered from sections of the teat cistern. C. boris was microscopically visible in ultralthin sections of streak canal and appeared closely associated with keratinaceous tissues. Numbers were greater than those enumerated by the broth method. There was no microscopic evidence of damage to streak canal tissue from C. boris in infected and noninfected tissues after staining with hematoxylin and eosin. Results suggest that C. boris is not established past Furstenberg's rosette.