This monograph has been reviewed by members of the IUMS–ICFMH Working Party on Culture Media and given ‘Proposed’ status.

This medium was developed by Miller et al. (1991) as a modification of xylose lysine deoxycholate agar for the isolation of non-typhi Salmonella spp. The selectivity relies on the use of the detergent Niaproof 4 (7-ethyl-2-methylundecan-4-yl sulfate, sodium salt), formerly Tergitol 4. Its diagnostic properties are based on the use of three indicator systems: xylose, lactose and sucrose combined with phenol red; lysine hydrochloride and also phenol red; sodium thiosulfate and iron. The low concentration of proteose peptone no. 3 incorporated in the medium produces blacker salmonella colonies in shorter incubation times (Miller et al., 1995). XLT4 inhibits many Gram-negative bacteria and provides good colonial differentiation between Salmonella and Citrobacter spp.