Isolation and identification of bacteria-
The isolation was done by transferring the colonies from nutrient agar plated to sterile enrichment broth media. These included MacConkeys broth (for detection of Staph.aureus) and Cetrimide broth (detection of P.aeruoginosa). The specimen tubes were incubated for 48 hours at 37 + 1 oC in inverted position for
24 hours and 507 days.
Allocation of mannitol salt agar B30-
The colonies grown on Vogel –Johnson’s medium was streak plated on sterile mannitol –salt agar medium for confirmation regarding presence/ absence of Staph. aureus . Pure staphylococcus culture ATCC 12600 was simultaneously streaked on separate plates to serve as positive control.
Further study of culture on selective media-
The colonies grown on Vogel- Johnson’s medium and MacConkeys medium were tested for Gram reactions and motility characteristics.
In order to further ensure that the organisms cultured on Vogel- Johnson’s and Mac Conkeys agar were probably E.coli, Staph. aureus or Salmonella species, the inoculums of the colonies from respective agar medium were employed in biochemical tests comprising of hydrolysis of starch, nitrate reduction, oxidase and catalase activity, liquefaction of gelatin, IMVic, Oxferm reaction etc.
The contents of this article belong to extensive laboratory work done by me to assess microbial contamination on few brands of dye and lake colors available in the market.