Fundamental Studies on the Bacteriophages for Typing Pseudomonas aeruginosa and Their Propagating Strains

Using the bacteriophages and their propagating strains shown in Table 1, lysogenicities of the strains, sensitivities of the strains to the phages and sensitivities of phage resistant mutants to the phages were tested to clarify specificities of the phages. Growth inhibition of the strains with low reproducibilities were observed by spotting the culture filtrates of the strains (Table 2). Applying plaque assay method, lysogenicities were found in 20 combinations (Table 3). Differences between two methods may be caused by different induction rates by the time and also by pyocine activities when undiluted filtrates were spotted. From these results, it can be said that there is no misreading caused by lysogenic phages in the stocks of typing phages when 1-3×10^6 PFU/ml solutions were applied. In addition, frequent host-induced modifications were observed among lysogenic phages originated from the same culture filtrate grown on different hosts (Table 4). Sensitivities of the propagating strains to typing phages were shown in Tables 5 and 6. The same host range between the two phages was not seen in each method except between phages 44 and 1214 in the method of spotting 10^9 PFU/ml. This result shows specificity of each phage, and possibility to select two out of four non-lysogenic strains for propagating 12 phages. Forty-nine kinds of phage resistant mutants were isolated from 11 strains except GN3405, and a total of 410 mutants were tested for sensitivity to the phages (Table 7-13). Thirteen cases gained the sensitivity to originally insensitive phages and 16 cases lost the sensitivities to all phages in almost all strains. Six kinds of phage 119X resistant mutants originally not sensitive to phage 21 retained the sensitivities to the other phages and two kinds lost also sensitivity to phage 21, but there was no phage 21 resistant mutant isolated. This result indicates that phage 119X is specific to the other phages but there is some relation between phages 119X and 21. Table 14 summarised cross-resistances between two kinds of phage resistant mutants. Cross-resistance was always observed between phages 7 and 352, 7 and M4, M4 and E79, 1214 and M4, E79 and M4, and M4 and C11, whereas no cross-resistances were found between 7 and 1214 or F8, 352 and 44, 1214, F8, E79 or C11, F8 and M4, 21 and C188, 119X and eight kinds of phages. Finally, the similarity indexes of the lytic spectra of two phages on 410 mutants show the correlation between phages 7 and 352, 44 and 1214, F8 and E79 which support the typing method of Sakamoto et al. (1977) and between 44 and F8, 44 and E79, 1214 and E79, M4 and C11 (Table 15)