Evaluation of Statens Serum Institut enteric medium for detection of enteric pathogens

The efficacy of the Statens Serum Institut (SSI) enteric medium for isolati on and direct identification of enteric pathogens was evaluated. Sis differ ent biochemical reactions can be read by using the SSI enteric medium, allo wing direct identification of a range of enteric pathogens, All 248 gram-ne gative bacterial species that were tested grew on the SSI enteric medium. O nly 10 of 248 bacteria (4%) showed discrepant results in the biochemical re actions, and none of these were enteric pathogens. Forty-three of 47 enteri c pathogens (92%) produced identical rates of semiquantitative growth on th e SSI enteric medium and 5% blood agar, whereas three Vibrio spp, and one A eromonas spp, showed reduced growth. Gram-positive bacteria did not grow on the SSI enteric medium, Most enteric pathogens had a detection limit of 50 bacteria per mi of feces, but higher numbers of Vibrio spp, and some Shige lla spp, were required for detection. The growth rates of 125 enteric patho gens and 12 Yersinia spp, on the SSI enteric medium, xylose lysine deoxycho late (SLD), Hektoen enteric (HE), Salmonella-Shigella (SS), and cefsulodin- irgasan-novobiocin (CIN) agar were compared, Detection rates after applicat ion of 200 CFU were 99% for SSI enteric medium, 92% for SLD, 88% for HE, an d 82% for SS agar, The 12 Yersinia spp, grew excellently on both the SSI en teric medium and CIN agar, We conclude that the performance of the SSI ente ric medium compares favorably to those of other media tested, Its ability t o detect Yersinia spp, may limit the number of media needed in the typical laboratory. The direct identification of enteric pathogens on the medium ma y also provide a more rapid diagnosis.