Nonfermenting gram-negative bacteria and their differentiation from Pseudomonas aeruginosa.

Pseudomonas aeruginosa strains and other nonfermenting Gram-negative bacteria isolated from surgical patients and environmental washings at a surgical in-patient department were characterized bacteriologically. The biochemical and cultivation features of 156 P. aeruginosa strains, 35 strains of oxidase-negative and 31 strains of oxidase-positive Gram-negative bacteria other than P. aeruginosa were studied. Nonpigmented P. aeruginosa strains and strains with delayed pigmentation accounted for, respectively, 8.3% and 21.2% of the P. aeruginosa isolates. Deviations other than pigmentation deficiency from typical characteristics of P. aeruginosa cultures included absence of the following activities: Glucose and xylose oxidation, gelatin liguefaction, proteolysis on milk agar and some others. Thirty-five strains of oxidase-negative nonfermenting Gram-negative bacteria were identified as Acinetobacter anitratus (21 strains), Moraxella lwoffi (11 strains) and Pseudomonas maltophilia (3 strains). Oxidase-positive nonfermenting Gram-negative bacteria (31 strains) were mainly represented by Pseudomonas alcaligenes (11 strains) and Pseudomonas cepacia (6 strains). Other species were isolated in individual cases only. The investigation scheme and tests proposed by Gaislerová (1977) allowed identification to species of most of the nonfermenting Gramnegative bacteria isolated.