Brucella melitensis Differs from B. suis in Growth and Urease Activity In-Vitro, and Infectivity in Fisher-344 Rats In-Vivo

Importance of urease activity on pathogenic differences among Brucella species was evaluated. In cell-free extracts, the B. suis urease showed 12 times greater specific activity than the B. melitensis urease. When Fisher-344 rats were inocu-lated intraperitoneally (IP), at 1 week post-inoculation (PI), B. melitensis wild type 16 M was recovered from spleens and livers in greater numbers than B. suis wild type 1330. At 8 weeks PI, spleens were clear of B. melitensis, whereas B. suis remained. The wild type and the urease deficient strains of B. suis did not differ from each other in terms of recov-ery from spleen or liver. Our observations suggest that B. melitensis induces greater acute infectivity in Fisher-344 rats, whereas B. suis causes chronic infectivity; and urease activity has no influence on Brucella infection using an IP route