THE PSEUDOMONAS–ACHROMOBACTER GROUP

Abstract

Fifty-three strains of nonpigmented Gram-negative rods which failed to produce acid in Kligler's iron agar were studied. Detailed examination revealed that many strains had been incorrectly identified as Alcaligenes. Sixteen strains were identified as Pseudomonas aeruginosa, and it was concluded that important identifying characteristics of this species are: (1) acid production from glucose, arabinose, and xylose, but not from lactose; (2) the ability to liquefy gelatin; (3) good motility and production of gaseous nitrogen in a motility–nitrate medium; and (4) a positive gluconate test. Thirty-seven strains appeared to be members of the genus Achromobacter and all produced acid from one or more carbohydrates. These strains were divided into three groups on the basis of (1) activity on gelatin, (2) nitrate reduction, and (3) motility. Some strains resembled Pseudomonas aeruginosa in such characteristics as reduction of nitrate to molecular nitrogen and oxidation of gluconate to 2-ketogluconate, but differed in that they neither liquefied gelatin nor peptonized and reduced litmus milk. More important, they had peritrichous flagella.