APPLICATION OF PULSED-FIELD GEL-ELECTROPHORESIS FOR DIFFERENTIATION OF VACCINE STRAIN RB51 FROM FIELD ISOLATES OF BRUCELLA-ABORTUS FROM CATTLE, BISON, AND ELK

Restriction endonuclease patterns of genomic fragments separated by us e of pulsed-field gel electrophoresis were used to differentiate Bruce lla abortus strain RB51, a rifampin-resistant mutant of the standard v irulent strain 2308, from other brucellae. Results were compared with results obtained by use of standard methods for characterizing brucell ae. Electrophoretic patterns of the ATCC type strains allowed identifi cation of the strains to the level of species. Genomic profiles of B a bortus biovars 1, 2, and 4 were similar, as were those of biovars 5, 6 , and 9. The profile of biovar 3 was similar to that of biovars 5, 6, and 9, except for a missing band at 93 kb and additional bands at 65 a nd 67 kb. A different fingerprint was detected in B abortus strain RB5 1, using the pulsed-field gel electrophoresis patterns of genomic DNA digested with restrictive endonuclease Xba I. The profile of B abortus strain RB51 contained a band at 104 kb, as opposed to a 109-kb fragme nt within profiles of B abortus isolates from naturally infected cattl e, bison, and elk. Despite known biochemical and biological difference s between RB51 and its parent strain (2308), restriction endonuclease analysis results were similar.