Protection by a polyvalent vaccine against challenge infection and pyelonephritis

The protective effect of immunization with a polyvalent vaccine (SolcoUrovac) was studied in the mouse and the rat. The i.m. immunization increased the resistance of mice to challenge infection with all homologous strains of bacteria. The LD50 values for E. coli, Proteus mirabilis and Streptococcus were 3.5-4.5 times and that of Klebsiella as much as 600 times that in nonimmunized mice. Protection against challenge with heterologous E. coli was also achieved and persisted for about 20 weeks. Immunization with the vaccine also provided marked protection against pyelonephritis in rats. Kidneys with abscesses were seen only one-third as often as in controls, and the size of the individual abscesses was substantially smaller in the vaccinated animals. Based on the quantity of bacteria in the kidneys it was postulated that the vaccination increased the clearance of bacteria.