Clinical isolates of Pseudomonads at this laboratory occasionally show mucoid colonial morphology, most of these being obtained from sputa, especially from those of patients suffering from chronic severe infection of the air way. Among 1, 658 strains of Pseudomonas obtained during these 2 years (1969, 1970), 199 mucoid strains (12.0%) were found.
In comparative studies on 16 tests with these mucoid and non-mucoid strains, some mucoid mutants failed to show the following chracteristics typical for Pseudomonas: Oxodation of glucose (8.7%), and reduction of nitrate to N₂ gas (26.1%). However, these atypical strains showed 100% positive results in tests for cytochrome oxidase, and acyl amidase test, and in pyocyanin production on King B medium.
These bacteriological characteristics of mucoid strains and their haunt in the air way of patients withchronic severe infection may suggests, as Doggett stated, that the mucoid strain is derived by mutationfrom non-mucoid original one under the influence of in vivo environments.