An aerosolized Brucella spp. challenge model for laboratory animals

To characterize the optimal aerosol dosage of Brucella abortus strain 2308 (S2308) and B. melitensis (S16M) in a laboratory animal model of brucellosis, dosages of 10(3)-10(10) colony forming units (CFU) were nebulized to mice. Although tissue weights were minimally influenced, total CFU per tissues increased beginning at 10(6)-10(7) CFU dosages, with 10(9) CFU appearing to be an optimal dosage for S16M or S2308 aerosol delivery. At 12 weeks after vaccination with 10(7) CFU of B. abortus strain RB51 (SRB51) or saline (control), mice were challenged intraperitoneally (i.p.) (6.4 x 10(4) CFU) or via aerosol (1.76 x 10(9) CFU) with S2308. Mice vaccinated with SRB51 had reduced (P < 0.05) splenic, liver and lung colonization (total CFU and CFU/g) after i.p. challenge with S2308 as compared with control mice after i.p. S2308 challenge. Control and SRB51-vaccinated mice did not differ (P > 0.05) in splenic, liver or lung colonization after aerosol S2308 challenge. Failure to demonstrate vaccine protection was not because of a high aerosol challenge dosage as colonization of spleen and liver tissues was lower (P < 0.05) after aerosol challenge when compared with control mice after i.p. S2308 challenge.