Dissociation in Pseudomonas aeruginosa.

Zierdt, C. H. (National Institutes of Health, Bethesda, Md.), and P. J. Schmidt. Dissociation in Pseudomonas aeruginosa. J. Bacteriol. 87:1003-1010. 1964.-Evidence is presented that dissociation of Pseudomonas aeruginosa occurs in vivo as well as in vitro, although it is suppressed in the blood stream. Of 116 primary cultures on blood agar, 77 (66%) had more than one colony type, with a range of 2 to 6 types per culture. Dissociation was studied in 14 primary cultures during 30 serial blood agar passages. Six of these did not dissociate. Of the six, three were originally primary monocolony strains, and three were strains with two colonial types. Seven of the remaining eight cultures had more than one colony type on the primary culture plate. These eight cultures were observed to dissociate at varying rates; 25 morphological and biochemical tests failed to reveal important differences in the colonial dissociants. However, they may be differentiated by bacteriophage action. Colonial morphology in a given strain of P. aeruginosa can be correlated with its bacteriophage lytic pattern, but patterns frequently undergo drastic change during subculture of the organism. The frequently seen different colonial forms in a specific primary culture are usually related, as proven by bacteriophage typing. Phenotypic colony changes after lysogenization were observed. Mucoid colonial variants are markedly more sensitive than are the nonmucoid to streptomycin, tetracycline, and chloramphenicol.