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Cytotoxicity of Mycoplasma mycoides subsp. mycoides Small Colony Type to Bovine Epithelial Cells

Institute of Veterinary Bacteriology, Vetsuisse Faculty, Universität Bern, Länggass-Strasse 122, Postfach, CH-3001 Bern, Switzerland,¹ INRA, Université de Bordeaux 2, UMR1090, 71, avenue Edouard Bourlaux, F-33883 Villenave d'Ornon, France,² Institute of Veterinary Virology, Vetsuisse Faculty, Universität Bern, Länggass-Strasse 122, Postfach, CH-3001 Bern, Switzerland³

Received 10 July 2007/ Returned for modification 7 September 2007/ Accepted 29 October 2007

The cytotoxicities of various strains of Mycoplasma mycoides subsp. mycoides small colony type (SC), the agent of contagious bovine pleuropneumonia (CBPP), were measured in vitro using embryonic calf nasal epithelial (ECaNEp) cells. Strains isolated from acute cases of CBPP induced high cytotoxicity in the presence of glycerol, concomitant with the release of large amounts of toxic H₂O₂ that were found to be translocated into the cytoplasms of the host cells by close contact of the Mycoplasma strains with the host cells. Currently used vaccine strains also showed high cytotoxicity and high H₂O₂ release, indicating that they are attenuated in another virulence attribute. Strains isolated from recent European outbreaks of CBPP with mild clinical signs, which are characterized by a defect in the glycerol uptake system, released small amounts of H₂O₂ and showed low cytotoxicity to ECaNEp cells. M. mycoides subsp. mycoides SC strain PG1 released large amounts of H₂O₂ but was only slightly cytotoxic. PG1 was found to have a reduced capacity to bind to ECaNEp cells and was unable to translocate H₂O₂ into the bovine cells, in contrast to virulent strains that release large amounts of H₂O₂. Thus, an efficient translocation of H₂O₂ into host cells is a prerequisite for the cytotoxic effect and requires an intact adhesion mechanism to ensure a close contact between mycoplasmas and host cells.

Published ahead of print on 12 November 2007.

Editor: F. C. Fang