Detection and enumeration of stressed coliforms

Different pretreatments were tried to recover Escherichia coli from food system and bacteriological diluents following freezing and thawing. The sublethally injured cells were found to repair their injury and start growing by resuscitating for 1 h in a non-nutrient medium at 37 degrees C. Longer periods did not give any improvement. Five media were studied for their recovery. Amongst the complex media, Eosine methylene blue agar was found to give maximum recovery. The organisms grew well on minimal medium also. Addition of vitamins and amino acids in the minimal medium did not show any increase in recovery. The results indicate that to detect index organisms such as E. coli from frozen systems, resuscitation in a non nutrient environment for at least 1 h necessary.