Interaction of virulent and non-virulent Rhodococcus equi human isolates with phagocytes, fibroblast- and epithelial-derived cells |
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Authors: | P. Nordmann N. Zinzendorf M. Keller I. Lair E. Ronco M. Guenounou |
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Affiliation: | Laboratoire de Microbiologie, Hôpital Raymond Poincaré, Facultéde Médecine Paris-Quest, UniversitéParis 5, 104 Bd Raymond Poincaré, Garches, France;Laboratoire d'Immunologie, Facultéde Médecine, Universitéde Reims, Reims, France;Abteilung Mikrobiologie, Biozentrum der Universität Basel, Basel, Switzerland |
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Abstract: | Abstract Rhodococcus equi is a facultative, intracellular, Gram-positive coccobacillus, increasingly reported in pneumonia of AIDS-infected patients. We investigated killing resistance properties of human R. equi virulent and avirulent human strains. Avirulent β-lactam-susceptible strains had lower intracellular colony forming units after 45 min incubation in murine macrophages J774 and human monocyte-macrophage TPH-1 than those of virulent strains. Only virulent β-lactam-resistant strains persisted within macrophages for at least 18 min only. A β-lactam-resistant mutant was obtained from a β-lactam-susceptible strain after selection in a penicillin G-containing culture medium. This mutant strain, like the natural virulent strains, persisted within macrophages, harboured cell-associated appendages, produced phage-like particles and induced, after its intravenous inoculation, a chronic infection in BALB/c nude mice. Supernatant culture of virulent strains transferred partial macrophage-killing resistance properties to avirulent strains. The same supernatant was toxic for L-929, HeLa and Vero cell cultures. These supernatant effects were heat-inactivated, trypsin-inactivated and did not seem to be linked to phage-like particle presence. These data argue that virulence, β-lactam-resistance, and macrophage-killing resistance are associated in human R. equi isolates. Moreover, only virulent strains produced uncharacterized toxic factors. |
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Keywords: | Rhodococcus equi Virulence Macrophage |
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