[The use of polyvinylpyrrolidone as a stabilizer in the lyophilization of Brucella]

Stabilizing effects of 5 percent aqueous polyvinylpyrrolidone (PVP) solution and sucrose-agar-gelatin medium (SAG) were examined in lyophilization of 4 Brucella types. The number of viable cells immediately after lyophilization in PVP has made up 48.1 percent on an average; this value was different with different Brucella species: 70.9 percent with B. abortus, 50.4 percent with B. melitensis, 41.2 percent with B. rangiferi, 30.2 percent with B. suis. Only 27.5 percent of cells were viable after Brucella lyophilization in SAG medium. Gradual death of lyophilized cells was observed in the course of strain storage at 5 degrees C. After two-year storage the number of viable cells after lyophilization in PVP was 41.8, after three-year storage 35.1 percent. The number of viable cells after SAG lyophilization was still lower. Biological characteristics of the strains lyophilized in both media corresponded to the initial ones over the three-year follow-up.