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Appl Environ Microbiol. 1969 September; 18(3): 452-457
Copyright © 1969 American Society for Microbiology. All Rights Reserved.

Comparative Study of the Efficacy of Seven Paper-Reagent Strips and Conventional Biochemical Tests in Identifying Gram-negative Organisms

Department of Laboratory Medicine, University of Minnesota School of Medicine, Minneapolis, Minnesota 55455
Department of Pediatrics, University of Minnesota School of Medicine, Minneapolis, Minnesota 55455
Department of Microbiology, university of Washington School of Medicine, Seattle, Washington 98105

ABSTRACT

Gram-nagative organisms were tested with commercially available reagentimpregnated strips (PATHO-TEC). Of the 291 strains, all were tested by using seven paper tests and their conventional counterparts. Excellent correlation was obtained with the oxidase, phenylalanine-deaminase, and Voges-Proskauer tests. Indole tests made on liquid medium cultures also gave complete correlation, but some false-negative results with indole-positive Proteus strains were obtained when growth from solid medium was tested by the strip method. Paper strip urease tests were positive within 2 hr with all Klebsiella and some Serratia, Herellea, and Citrobacter strains as well as with Proteus strains. Approximately 15% of citrate strip test results differed from those of the conventional tests, and reproducibility was poor on retest. The lysine decarboxylase strip test showed a number of discrepancies and posed problems of interpretation and readability. Paper reagent strip methods are simple and convenient and merit further development to increase the specificity of those which depend on pH change up to that achieved with the Voges-Proskauer, oxidase, phenylalanine, and indole methods.