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Vet. Res.
Volume 38, Number 5, September-October 2007
Page(s) 685 - 696
Published online 23 June 2007
How to cite this article Vet. Res. (2007) 685-696
Vet. Res. 38 (2007) 685-696
DOI: 10.1051/vetres:2007026

Staphylococcus aureus leucotoxin LukM/F' is secreted and stimulates neutralising antibody response in the course of intramammary infection

Pascal Rainard

INRA, UR1282 IASP, 37380 Nouzilly, France

(Received 8 December 2006; accepted 30 March 2007 ; published online 23 June 2007)

Abstract - Leucotoxins are regarded as virulence factors of Staphylococcus aureus, but data supporting their importance in infection are scarce. Experimental infections of the mammary glands of six goats with a leucotoxin-producing strain were used to investigate in vivo production of leucotoxin. Leucotoxin M/F' was monitored in milk as well as antibodies to LukM/F' in serum and milk. Leucotoxin antigen was detected by ELISA in milk samples of two goats. The appearance of neutrophils in these samples showed similarity with the altered appearance of neutrophils incubated with purified LukM/F' leucotoxin. Leucotoxic activity was found in the milk samples of these two goats, in particular those of the only goat which developed gangrenous (necrotic) mastitis, and this activity was inhibited by antibodies to LukM/F'. Increases in specific antibody titers occurred in the serum and milk of infected goats, and neutralizing titers increased in serum. The results indicate that the lukM and lukF' genes were functional in vivo, and actively transcribed and translated in the course of mammary infection. These results suggest that LukM/F' can interfere with neutrophil defense activities during infection, and they prompt further studies to investigate the contribution of leucotoxins to staphylococcal mastitis.

Key words: Staphylococcus aureus / leucotoxin / mastitis / ruminants

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© INRA, EDP Sciences 2007