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

Abstract

Gram-negative 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 Serralia, 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.

Microfermentation Series for Identification of Single Colonies of Enterobacteriaceae

“…Citrobacter, Arizona, and Proteus sp. were negative at 18 hr, weakly positive at 24 hr, and strongly positive at 48 hr. Attempts were made to make these reactions more rapid by decreasing the concentration of K2HPO4 or by adding increments of NH4Cl as an extra source of nitrogen.…”

Evaluation of the pathotec Rapid I-D system for identification of Enterobacteriaceae

“…In many studies and evaluations of these products, their accuracy and reliability varied. In 1971, Martin et al (3) reported that their studies verified those of Matsen and Sherris (4) in that cytochrome oxidase, phenylalanine, indole, and Voges-Proskauer (VP) strip tests were reasonably reliable, but urease, lysine, and citrate strip tests were not reliable, for the identification of Enterobacteriaceae. In 1973, Blazevic et al (1) and Rosner (5) reported independently on evaluations of an improved set of strips, the Pa-thoTec Rapid I-D System, but results in these two laboratories were substantially different in many respects.…”

Evaluation of the PathoTec “Rapid I-D System”

“…The PathoTec system consists of 10 reagentimpregnated strips designed to determine biochemical characteristics of the Enterobacteriaceae within 4 h. Previous performance tests evaluating some of these strips showed the accuracy of some and deficiencies of others (1,5). Based on these evaluations, many of the strips have been redesigned and are now available either separately or in a kit of 10 for the identification of the Enterobacteriaceae.…”