Experimental Infection with Pseudomonas aeruginosa in Mice

ABSTRACT Comparative studies on the virulence of 22 clinical isolates of Pseudomonas aeruginosa were made by means of intraperitoneal inoculation in mice. The LD 50 values of these strains for mice ranged from 10 5 0 to 10 7.5 viable cells per mouse and the average was 10 6.6 . The virulence of certain strains was significantly enhanced when these strains were inoculated mixed with mucin. The highly virulent strains were often found among the strains which were serologically untypable though no relationship could be found between the virulence of test strains and their other biological characteristics such as pigments, hemolysins and extracellular enzymes. The facts suggest that pigments and extracellular enzymes play no important role in the pathogenicity of P. aeruginosa for mice. Moreover, no difference was seen on virulence among the strains isolated from the patients and healthy carriers. The susceptibility of ICR, ddN and CF#1 mice for P. aeruginosa was investigated. There was no clear difference in susceptibilities to P. aeruginosa infection.