Evaluation of a rapid method to exclude the presence of certain enteric pathogens in stool specimens

Abstract

A new commercial method intended to exclude the presence of Salmonella spp., Shigella spp., and Yersinia enterocolitica and to presumptively identify Salmonella isolates within 2 h after primary isolation from stool specimens was evaluated. This system is marketed in Europe as API Z and in the United States as Rapid SST. The strip consists of five pairs of cupules for the screening of five lactose-negative colonies. The first cupule of each pair detects the presence of five enzymatic activities, whereas the second serves to maintain the strain for additional testing if necessary. A total of 197 fresh isolates from stool specimens and 217 stock cultures of Salmonella spp., Shigella spp., and Yersinia enterocolitica were tested, with the API 20E system as a reference method. In the stool specimens, 77.3% of the bacteria could be excluded from further workup for the presence of these organisms within 2 h. Over 97% of the stock strains and each of three fresh Salmonella isolates tested produced a reaction pattern corresponding to a correct presumptive identification. This reaction pattern was not produced by any isolate other than the Salmonella isolates. The API Z system can be used as a screen for the presence of Salmonella and Shigella spp. and can provide an accurate presumptive identification of Salmonella isolates within 2 h after primary isolation.

Rapid biochemical screening for Salmonella, Shigella, Yersinia, and Aeromonas isolates from stool specimens

“…Various techniques for the rapid detection of enteropathogenic bacteria have been proposed, including same-day biochemical screening (1,3,5,7,8) and antigen detection (3, 6). In the study described here, we evaluated a system of four rapid (4 to 6 h) biochemical screens (RSs) for the presumptive identification of Salmonella, Shigella, Yersinia, and Aeromonas isolates from enteric isolation media and compared the results with those of a conventional two-tube 24-h screen.…”

Rapid automated method for screening of enteric pathogens from stool specimens

“…Salmonella, Shigella, and Yersinia species are classically screened from stools by inoculating the suspicious colonies, isolated on enteric differential agar media, onto conventional biochemical test media, which usually require a 24-h incubation period. This length of time for screening of some enteric pathogens can be significantly reduced by using new, faster methods (2,(4)(5)(6)(7), making possible a preliminary report within the same day.…”

Evaluation of rapid SYS system as screen for Yersinia enterocolitica in the United States

“…The API Z system was subsequently distributed in the United States by DMS Laboratories (Flemington, N.J.), which extended the screening claim to include Yersinia enterocolitica and changed the product name to Rapid SYS. The sensitivity and specificity of the Rapid SYS system reportedly ranged from 98.7 to 100% and 54 to 77%, respectively (2,3,5). Falsely elevated estimates of specificity of the Rapid SYS system were reported as a result of the inaccurate interpretative criteria provided by the vendor.…”