>Year 2003, Issue 4
Flores-Abuxapqui JJ, Puc-Franco MA, Heredia-Navarrete MR, Vivas-Rosel ML, Franco-Monsreal J
Comparison between sodium selenite and sodium tetrathionate broths, incubated at 37°C and 42°C for the isolation of Salmonella spp. from faeces of carriers
Rev Biomed 2003; 14 (4)
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Introduction. Enrichment broths are particularly helpful in the recovery of Salmonella from carriers in whom the number of microorganisms may be as low as 200CFU/g of faeces. In the techniques of isolation of Salmonella in sanitary microbiology, the incubation of enrichment broths at 42°C has been used to allow a greater recovery of the bacteria when it exists in very small quantities or when it needs to be isolated from very contaminated sources.
Material and Methods. 2,080 samples of faeces from children without diarrhea were studied. They were inoculated in sodium selenite and sodium tetrathionate broths, which were incubated at 37 and 42°C, and streaked on XLD agar plates.
Results. Eighty seven (4.2%) samples were positive for the isolation of Salmonella spp. Fifty two (2.5%) samples were positive with sodium selenite broth incubated at 37°C, and 54 (2.6%) at 42°C. The total of positive samples with sodium selenite broth was 57 (2.7%). Seventy one (3.4%) samples were positive with sodium tetrathionate broth at 37°C, and 73 (3.5%) at 42°C. The total of positive samples with sodium tetrathionate broth was 76 (3.7%). Salmonella was isolated in 9 (0.4%) samples streaked directly on XLD agar plates.
Discussion. We found that sodium tetrathionate broth is better than sodium selenite as enrichment medium, and we recommend it for routine clinical work. On the other hand, if we carry out an epidemiological study to detect carriers, the addition of sodium selenite broth at both temperatures would be useful.
||Salmonella, enrichment broths, carriers.
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>Year 2003, Issue 4