A total of 431 strains of
Pseudomonas aeruginosa originated from such laboratory animals as mice and guinea pigs, domestic animals, and nature were examined for serological typing, virulence for mice, and susceptibility to six antibiotics by the agglutination method of Homma et al., the intraperitoneal and subcutaneous infection of mice, and the plate dilution method, respectively. The results obtained are summarized as follows.
1) Of the 431 strains, 428 (98.4%) were agglutinated with only one type serum and 6 (1.4%) with 2 type sera, but 1 (0.2%) was not agglutinated with any of the type sera. Changes in serotype of
P. aeruginosa occurred to 24 (5.9%) of the 405 strains which had been preserved for about 85 days by subculturing several times on heart infusion agar slants.
2) Of 380 strains of
P. aeruginosa isolated from mice and guinea pigs, 374 were typed into serotype 10. Of 51 strains isolated from dogs, cattle, and pathological specimens from animals, soil, and water, 1, 2, 2, 3, 5, 3, 2, 22, 3, and 5 strains belonged to serotypes 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10, respectively.
3) The 431 strains of
P. aeruginosa were examined for virulence for mice. The median of LD
50 values by intraperitoneal infection was 10
6 viable cells per mouse within a range from 5.0×10
4 to 9.9×10
7, while that by subcutaneous infection was 10
7 viable cells per mouse within a range from 1.0×10
5 to 9.9×10
8.
4) The 431 strains of
P. aeruginosa were tested for susceptibility to 3', 4'-dideoxykanamycin B (DKB), gentamicin (GM), carbenicillin (CB-PC), chloramphenicol (CP), polymyxin-B (PL-B), and colistin (CL). Most of them were susceptible to from 6.25 to 12.5mcg/m
l of DKB, 12.5 to 25mcg/m
l of GM, 100 to 200mcg/m
l of CB-PC, 6.25 to 25mcg/m
l of PL-B, and 125 to 1, 000 units/m
l of CL. About 50% of these strains were susceptible to 400mcg/m
l of CP, but the other strains were resistant to the same dose of CP.
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