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

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. Staphylococcus aureus / leucotoxin / mastitis / ruminants

LukMF′ is the major secreted leukocidin of bovine Staphylococcus aureus and is produced in vivo during bovine mastitis

“…LukMF′-negative strains, such as Newbould, also cause mastitis in cattle, showing that LukMF′ is not a prerequisite for S. aureus to cause an intramammary infection and that other toxins or virulence factors also play a role in the pathogenesis of mastitis. However, whereas the LukMF′-negative strain Newbould causes mostly mild clinical symptoms38, infections with the LukMF′-positive isolates RF122 and Ch122 are characterised by severe forms of mastitis3839. In accordance with our results, Rainard et al 39.…”

Ultrasound and histopathological investigations of experimentally induced Staphylococcus aureus mastitis in goats

“…During that period however, clinical signs of inflammation have appeared (painfulness, hyperaemia, skin that feels warm to the touch, swelling), which became more pronounced by post infection hour 48. Similar results in goats were observed by other authors after experimental induction of mastitis with high doses of S. aureus (Reinoso et al, 2002;Ma et al, 2007;Rainard, 2007).…”

“…They have used various infection doses depending on the research goal (van Herwijnen, 2010). In goats, clinical S. aureus mastitis was reproduced with doses of 18 × 10 3 (Rainard, 2007), 1 × 10 4 and 1 × 10 8 cfu (Ma et al, 2007). Lasagno et al (2012) have followed the course of experimentally induced subclinical mastitis in goats, inoculated with Streptococcus uberis at a dose of 1.7 × 10 8 cfu.…”

The Bicomponent Pore-Forming Leucocidins of Staphylococcus aureus

“…Purified recombinant LukMF= is toxic to bovine neutrophils and macrophages and is capable of binding to murine neutrophils, macrophages, and T cells (123,237,238). It is the most potent leucocidin on cells of bovine origin and can be isolated from the mammary glands of cows with severe mastitis (239). Infected cows can elicit an immunological response to LukMF=, as antibody can be isolated from serum during the course of infection (239).…”

“…It is the most potent leucocidin on cells of bovine origin and can be isolated from the mammary glands of cows with severe mastitis (239). Infected cows can elicit an immunological response to LukMF=, as antibody can be isolated from serum during the course of infection (239). Whether these associations indicate that LukMF= plays a significant role in the pathogenesis of mastitis remains to be determined.…”