Serological Typing of Pseudomonas aeruginosa and Its Cross-infection

Considering the properties of colonial dissociation of Pseudomonas aeruginosa, the following method was tentatively established for the serological typing of this organism.a. A type la colony must be selected from the bacterium to be tested, and cultivated on nutrient agar at 37°C overnigt. The resulting culture was used as an agglutinogen. A type sm should be avoided, since it usually showed a tendency to agglutinate spontaneously.b. The culture was suspended in a phosphate buffer saline (pH 7.2) and heated at 120°C for 90 minutes. After it was collected, the heat-killed celles were resuspended in the same solution and used as an agglutinogen.c. Type la cells were heated at 100°C for one hour and used as an antigen to immunize rabbits. When the agglutination titer was found to be more than 400, the animal was exsanguinated. Serum was collected, heated at 56°C for 30 minutes, diluted to such extent as to make the titer 10, and used for agglutination tests.d. Twelve strains were selected for high specificities of their serological properties and used for preparing twelve type-sera, from T1 to T12.2. Agglutination tests using the ten type-sera were made on 915 strains of P. aeruginosa isolated from patients. In consequence, 656 strains (16%) with two or more type-sera, among which 98 strains (9%) being agglutinated with two type-sera. Strains belonging type 5 were found the most predominant both in the results of the first tests using 10 type-sara and those obtained by the second investigations using 12 type-sera.3. Cross-infection took place in many hospitals, especially in tuberculosis wards. Remarkable cross-infection was found among the sputa and stools of tuberculosis patients in the same ward.4. As for mice, the percentage of isolation of P. aeruginosa from feces varied markedly by the breeding place. It was 100% or null, and almost all the strains isolated in one breeding place belonged to the same serotype. This result indicates that P. aeruginosa infection was cross-infection in the case of mice.