A comparative study of the 'rhodochrous' complex and related taxa by delayed-type skin reactions on guinea pigs and by polyacrylamide gel electrophoresis.

Cell extracts prepared by ultrasonic disruption of 17 strains of the 'rhodochrous' complex and related taxa were compared by polyacrylamide gel electrophoresis and for immunologic relatedness, by skin test reactions. Two organisms, Jensenia canicruria and Nocardia calcarea, gave similar gel patterns and skin test reactions, and are considered to be identical. Extracts of nocardia rubra showed a strong antigenic relationship with those of three Nocardia pellegrino organisms (N325, N324 and N420) previously assigned to the 'rhodochrous' complex. Two Gordona organisms appeared to be less antigenically related to the 'rhodochrous' complex. Extracts of three of four organisms designated Lspi (Rhodococcus coprophilus Rowbotham & Cross 1976) elicited skin test reactions similar to those of the 'rhodochrous' strains. One Lspi strain, N650, showed striking similarities to the 'rhodochrous' complex strain N420 (Nocardia pellegrino).