One handred and fourty strains of Pseudomonas aeruginosa (Ps. aerug.) isolated from clinical materials in the Hokkaido University Hospital during 1970 to 1971 were typed serologically by means of Homma's agglutination method utilizing a routine set of 13 standard sera, and susceptibilities of them to several kinds of antibiotics were determined. The results obtained were compared with those of our previous report in 1970.
One handred and twenty-five strains (89.3%) were typable with an occurence of type T5 in 43 strains (30.7%), type T8 in 38 (27.1%), type T7 in 12 (8.6%), type T10 in 11 (7.9%) and small numbers of strains were distributed in the other types. Three strains showed agglutination with two standard sera simultaneously and twelve strains (8.6%) were nontypable.
The strains of Ps. aerug. were resistant to common antibiotics such as streptomycin and kanamycin, with minimum inhibitory concentrations (MIC) of more than 25mcg/ml, the level obtainable in the sera by usual dosage of these drugs.
A peak of MIC distribution in carbenicillin and sulbenicillin was at 100mcg/ml and cross resistance was observed between these two antibiotics. Twelve per cent of strains were found to be highly resistant to both antibiotics with MIC of 400mcg/ml or more, a finding which was not observed in our previous study in 1970. Emergence of highly resistant strains to gentamicin, colistin and polymixin B was not observed.
The type T5 strains were found to be more resistant to the above mentioned six antibiotics tested than the type T8 strains except for sulbenicillin.
