Description
Tryptone Soya Broth, w/ Ferrous Sulphate is used to pre enrich Salmonella during isolation from egg specimens in accordance with FDA BAM. Salmonella constitute the most taxonomically complex group of bacteria among the Enterobacteriaceae. Human Salmonella infections are most commonly caused by ingestion of food, water or milk contaminated by human or animal excreta. Contaminated eggs or foods containing eggs have also been a source of food borne salmonellosis, with a significant proportion of these outbreaks being attributed to Salmonella Enteritidis. Since the level of contamination in individual eggs or a pool of such eggs may be low, enrichment to increase cell numbers can take several days. Pre-enrichment of raw blended eggs with medium supplemented with ferrous sulphate, significantly enhance the growth of Salmonella. Disinfect eggs with 3:1 solution of 70% alcohol and 5% iodine/potassium iodide solution. Eggs are cracked aseptically by gloved hands and mix samples thoroughly until yolks are completely mixed with the albumen. These are incubated at room temperature (20-24?C) for 96 ? 2 h. After 96 ? 2 h, remove 25 ml of this mix and add to 225 ml Tryptone Soya Broth, w/ Ferrous Sulphate. After incubation for 24 ? 2 h at 35?C, transfer 0.1 ml mixture to 10 ml Rappaport-Vassiliadis medium and another 1 ml mixture to 10 ml tetrathionate broth. Vortex and incubate at optimum temperature for 24 ? 2 h depending upon the microbial load and type of the sample. These are further subcultured into XLD Agar or Hektoen Enteric Agar, incubate the plates 24 ? 2 h at 35?C and observe for the appearance of typical salmonellae colonies. Blue-green to blue colonies will be appeared in XLD Agar and pink colonies with or without black centers on HE Agar.
