Selective media for isolation of Brucella abortus strain RB51

Brucella abortus strain RB51 (SRB51) is the standard vaccine used to protec t cattle against brucellosis and is currently being used to vaccinate bison in the United States (US). Currently available media for culture of Brucel la have not been evaluated for their ability to support growth of SRB51. In this study, five selective media for isolating brucellae, four commerciall y available media for gram-negative bacteria, and tryptose agar with 5% bov ine serum (TSA) were compared to two SRB51 selective media developed in thi s study (rifampin brucellae medium (RBM), and malachite green brucellae med ium (MGB)), for their ability to support growth and enhance recovery of SRB 51. Four of the five media currently used for isolation of brucellae and tw o of the four media used for other Gram-negative bacteria did not support g rowth of SRB51. Modified Kuzdas and Morse (MKM), Brilliant Green, Skirrow's , RBM, and MGB supported growth of SRB51 in a manner similar to TSA. Recove ry of SRB51 from tissues of SRB51-vaccinated bison was attempted on TSA, MK M, RBM, and MGB. From a total of 436 samples, SRB51 was isolated from 9.6, 4.3, 5.5, and 9.0% on TSA, MKM, RBM, or MGB media, respectively. Strain RB5 1 was recovered on only one medium (nine on TSA; three on RBM; and 9 on MGB ) from 21 samples. Overgrowth of contaminating bacteria prevented potential detection of SRB51 from 9.4, 5.5, 0.07, and 5.9% of samples on TSA, MKM, R BM, or MGB, respectively. These data suggest that the use of RBM and MGB, i n combination with TSA, enhances the ability to recover SRB51 from tissue s amples. Published by Elsevier Science B.V.