Changes in ovine erythrocyte morphology due to sphingomyelin degradation by Corynebacterium pseudotuberculosis phospholipase D.

Corynebacterium pseudotuberculosis produces a sphingomyelin-specific phospholipase D exotoxin that is a major determinant in the pathogenesis of caseous lymphadenitis. We assessed the changes induced in the morphology and sphingomyelin concentration of ovine erythrocytes after incubation with broth culture filtrates or purified exotoxin. Sphingomyelin was hydrolysed nearly in parallel with shape change. Morphologically, spherostomatocytes were seen initially, and later these contained numerous vacuoles at the periphery. Vacuoles seen in thin sections with transmission electron microscopy appeared as pits with scanning electron microscopy. Pitting became progressively worse with time, leading to extensive scalloping of the membrane surface. Chemically, significant decreases (P less than or equal to 0.05) in erythrocyte membrane sphingomyelin content and significant increases (P less than or equal to 0.05) in the content of glycerophospholipids (i.e. phosphatidylglycerol) were observed in erythrocytes incubated with broth culture filtrates or purified exotoxin. These alterations may contribute to the pathophysiology of acute infections induced by C. pseudotuberculosis.