Survival of Brucella abortus strain RB51 lyophilized and as liquid vaccineunder different storage conditions

Brucella abortus strain RB51 (SRB51) is a new cattle vaccine that is approv ed for use in the U.S. for prevention of brucellosis. At the present time, other countries are implementing or considering the use of SRB51 vaccine in their brucellosis control programs. In the current study, the effect of th ree stabilizing media, two fill volumes (1 and 3 ml), and three storage tem peratures (-25, 4 and 25 degreesC) on the viability of lyophilized SRB51 ov er a 52 week period was determined. The effects of three concentrations of bacteria (5 x 10(8), 1 x 10(9), or 5 x 10(9) cfu/ml) and two storage temper atures (4 or 25 degreesC) on viability of liquid SRB51 vaccine were also de termined. For lyophilized strain RB51 vaccine, fill volume did not influenc e viability (P>0.05) during lyophilization. Although fill volume did not in fluence viability during storage in World Health Organization (WHO) media o r media containing both WHO and Lactose Salt (LS) media, 1 mi fill volumes of SRB51 in LS media had greater (P<0.05) viability when compared to 3 mi f ill volumes. Lyophilized SRB51 vaccine stored at 25<degrees>C had a more ra pid decline in viability (P<0.05) when compared to vaccine stored at -25 or 4<degrees>C. With the exception of the 3-ml fill volumes of LS media, all three stabilizing media were similar in maintaining viability of SRB51 at - 25 degreesC storage temperatures. However, when compared to WHO or WHO/LS m edia, stabilization in LS media was associated with a more rapid decline in viability during storage at 4 or 25 degreesC (P<0.05). Initial SRB51 conce ntration in liquid vaccine did not influence (P>0.05) viability during stor age at 4 or 25 degreesC. When compared to liquid SRB51 vaccine stored at 25 degreesC, storage at 4 degreesC was associated with a slower decline in vi ability (P<0.05) during 12 weeks of storage. Biochemical and morphological characteristics of SRB51 were stable under the storage conditions utilized in the present study. This study suggests that viability of SRB51 can be re adily maintained during storage as a lyophilized or liquid brucellosis vacc ine.