New plate medium for screening and presumptive identification of gram-negative urinary tract pathogens

Abstract

A new selective, differential plating medium to screen the common gram-negative urinary tract pathogens is described. The medium combines adonitol fermentation, phenylalanine deaminase, and β-glucuronidase tests and allows the indole and cytochrome oxidase tests to be performed directly from the plates. High-level agreement with individual conventional tests was recorded in comparative studies with 504 cultures of gram-negative rods. There was 100% agreement, except for the Providencia spp. indole spot test (61.6% agreement). Adonitol fermentation by Providencia species could not be determined. Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, and Pseudomonas aeruginosa were identified with a high efficiency (100, 85.7, 83.5, and 100%, respectively) without further testing. There was 96% overall agreement for the 267 infected urine samples tested.