Resistance of Rhodococcus equi to acid pH

Rhodococcus equi is an important gram-positive intracellular facultative pa thogen in foals of less than 3 months of age, that causes suppurative bronc hopneumonia, lymphadenitis and/or enteritis. The disease in young foals mai nly occurs in spring and summer when weather conditions are favorable for s urvival and multiplication of the bacteria in the environment. R. equi is w idespread in the environment of horsebreeding farms: it has been isolated f rom the soil of paddocks and from the feces of adult horses and foals. Aero sol infection via dust of paddocks seems to be the major route of foal infe ctions. The molecular mechanisms associated with the pathogenesis an not we ll understood and little is known about the markers or factors associated w ith virulence of R. equi. However, the discovery of a large plasmid in viru lent strains and its association with virulence in mice and in young foals was reported. In this report, we studied the acid resistance of virulent R. equi in comparison with its avirulent plasmid-free isogene. (C) 2000 Elsev ier Science B.V. All lights reserved.