Characterization of United Kingdom Isolates of Corynebacterium pseudotuberculosis Using Pulsed-Field Gel Electrophoresis

Caseous lymphadenitis is a chronic suppurative disease caused by Corynebacterium pseudotuberculosis and is responsible for serious economic losses to the sheep and goat industry. Caseous lymphadenitis was first reported for goats in the United Kingdom in 1990 and for sheep in 1991. Recent evidence suggests that the prevalence of the disease within the national flock is increasing. Fifty isolates of C. pseudotuberculosis from the United Kingdom comprising sheep and horse isolates, the original goat outbreak strain, and the type strain were characterized by biotyping, antimicrobial susceptibility, production of phospholipase D, and genotyping by pulsed-field gel electrophoresis using SfiI and SmaI. All of the isolates were confirmed as C. pseudotuberculosis, and all produced phospholipase D but none reduced nitrate. Restriction with SfiI generated 16 to 18 bands between 48.5 and 290 kb and differentiated six pulsotypes. We conclude that 80% of the strains tested were epidemiologically related to the outbreak strain and that the equine profile was distinct both phenotypically and genotypically.