[A comparison of methods for the enrichment of Salmonellae from human feces]

Abstract

154 samples of faeces contaminated with salmonellae belonging to 21 species were investigated each in 23 enrichment broths for compare the efficiency. The best results were obtained with selenite cystine broth (no. 5) followed by Rappaport broth (no. 17) and tetrathionate brilliant green bile broth - TBG - (no. 12); see also Fig. 1-4 and Tables 3 and 4. S. typhi is recovered the best by selenite broths. Rappaport broth seems to be the optimal enrichment broth for the most salmonellae with exception of S. typhi, S. bovismorbificans, and some other species. Preuss's modification of tetrathionate enrichment broth was significantly more efficient than Muller-Kauffmann's tetrathionate. Brilliant green bile broths are not very selective. Its efficiency is comparable with unselective broths without any inhibiting substances. The unspecific broths show a little enrichment effect during short incubation times. Therefore, they are used for preenrichment. However, incubation during 24 h is recommended for optimal recovery in selective enrichment broths, i.e. Rappaport, selenite, and tetrathionate media. The selenite broth should be used unconditionally for detecting salmonellae in human faeces. It should be combined additionally with Rappaport or tetrathionate broth in the modification of Preuss but not of Muller-Kauffmann.