Identification of Nonfermenting Gram-negative Bacilli in the Clinical Laboratory.

Much has been written and said in recent years regarding the classification and significance of the Enterobacteriaceae. These organisms, without a doubt, exceed all other gram-negative bacteria as etiologic agents of disease, and because of their predominance they have deserved the attention that they have received. With the emphasis placed on these fermenting bacteria, however, a dearth of information on nonfermenting gram-negative bacteria has appeared in textbooks, particularly those used for medical bacteriology. Consequently, the clinician and the laboratory workers have been in the difficult position of not knowing the significance of the nonfermenting gram-negative organisms. Only recently has the literature included more information on the nonfermenting gram-negative organisms, particularly about their physiology and taxonomy. The taxonomic designation of organisms in the families Pseudomonadaceae, Achromobacteraceae and the "illegitimate" (4) children of the family, Parvobacteriaceae (2) is still in a state of flux. Arguments, requests, and opinions in the literature concern the legality, appropriateness, and priority of names. It would appear that most bacteriologists agree as to the biochemical nature of these organisms, [-whether they be called "Pseudomonas aeruginosa" or "P. pyocyanea," "Mima polymorpha" or "Moraxella nonliquefaciens," "Herellea vaginicola" or "Bacterium anitratwn."] The purpose of this paper is not to add to the confusion in taxonomy but to indicate some methods that will provide easy recognition and preliminary classification of the nonfermenting gram-negative bacilli. These organisms are first recognized in the laboratory by the lack of fermentation on differential media such as eosin-methylene blue-agar