Nonmotile varieties of Pseudomonas aeruginose producing melaninlike pigment.

The existence of a variety of Pseudomonas aereginosa that produced a melaninlike pigment was first reported by Radais (Compt. rend. soc. biol. 49:808, 1897) and confirmed by Gessard (Ann. inst. Pasteur 15:817, 1901). A strain of nonmotile gram-negative bacillus (1184) was isolated in this laboratory from the urine of a man with chronic pyelonephritis. The organism l)roduced a melaninlike pigment on nutrient agar. The liquefaction of gelatin was slow. The l)rocluction of the melaninlike pigment was almost absent in the gelatin medium but a slight tinge of green was noted. Extraction of the growth on Trypticase Soy Agar (BBL) with chloroform confirmed the presence of pyocyanine. Since P. aeruginosa is rarely nonmotile, the question arose as to whether this organism was a nonmotile variant of P. aeruginosa or a different species. Agar diffusion identification tests (Liu, J. Bacteriol. 81:28, 1961) and neutralization tests of its protease (Liu, Abe, and Bates, J. Infectious Diseases 108:218, 1961) with antisera of P. aeruginosa confirmed the identity of the organism as a variant of P. aeruginosa. A similar, nonmotile bacillus producing melaninlike pigment was isolated by Inoue (J. Am. Med. Women's Assoc. 16:858, 1961) from blood of a patient with sepsis in Japan. This organism (117) was also identified by the author as P. aeruginosa.