In the present study, 17 Rhodococcus equi isolates from animals and 13 R. equi isolates from humans were correctly identified by the use of the API Coryne-test system. The biochemical characteristics revealed no significant differences between isolates from animals and humans. Heat extractions at acid p H or autoclave extractions of the bacteria and the use of monospecific antisera against type antigens 1-7 allowed the serotyping of the bacteria. The majority of the R. equi isolates reacted with serotype 1 and serotype 2-specific antisera, extracts of two human isolates reacted with serotype 5 and serotype 6-specific antisera, respectively. The determination of biochemical and serological properties of R. equi might help to characterize individual cultures of this species. This might be useful in epidemiological studies. U.S.
Summary
In this study, 45 Rhodococcus equi isolates from animals and humans were identified by the Api Coryne system, and serologically with monospecific antisera against capsular types 1–7, with serotypes 1 and 2 predominating. Regardless of serotype, 14 out of 31 isolates from animals and one of 14 isolates from humans expressed 15–17‐kD virulence‐associated proteins. In hexadecane adherence studies, serotype 2 isolates generally displayed hydrophobic surfaces. In addition, isolates of serotype 1 generally haemagglutinated erythrocytes from rabbits. Neither property appeared to be related to the occurrence of the virulence‐associated proteins. By contrast, the haemagglutination reaction correlated significantly with the adherence of the bacteria to HeLa cells. This adhesion might serve as additional marker of virulence among isolates of R. equi and might be useful in epidemiological studies.
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