4), this particular strain has the same colony appearance as other Salmonella isolates – distinctive red colonies.īecause of the risks associated with reporting false negative results with such atypical Salmonella strains, ISO-6579 (Microbiology of the food chain - Salmonella) requires laboratories to use XLD agar and a second selective media of your choosing. The typical composition corresponds to that defined in the American and European Pharmacopeia. 3) and CHROMagar™ Salmonella Plus (see Fig. TECHNICAL DATA SHEET XLD AGAR DETECTION OF SALMONELLA INTENDED USE XLD (Xylose Lysine Desoxycholate) Agar is used for the isolation of Salmonella in pharmaceutical products. XLD stands for xylose lysine deoxycholate. Hektoen Enteric Agar (HEA) was developed in 1967 by King and Metzger of the Hektoen Institute in order to improve the isolation of Shigella and Salmonella organisms when compared with other media frequently utilized at that time.1,2 This medium is considered to be moderately selective, and is particularly useful in the isolation of Shigella spec. Such colony characteristics on XLD would result in these Salmonella isolates being reported as a false negative (as their appearance is typical of a coliform isolate).Īs shown below when grown on Rambach™ agar (see Fig. XLD agar is a selective, differential, and indicator medium for the isolation of enteric pathogens. These Salmonella colonies are yellow without the black dot (see Fig.2 above), instead of the expected red with a black dot for a typical Salmonella (see Fig.1 above). These characteristics lead to an atypical colony appearance on this media. The particular strain of Salmonella implicated in the recent contamination of infant formula milk, is from the S.agona species group and has very unusual behaviour on XLD, ie non-alkalinisation of the medium and no H2S reaction. The swabs were inoculated directly onto Salmonella-Shigella (SS) agar, Xylose Lysine Desoxycholate (XLD) agar, MacConkey (MA) agar and alkaline peptone broth.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |