Expert: Walter Hintz - 12/4/2009

Question
You are given a mixed culture containing from 1 to 4 organisms. You are to identify these organisms. What would you do beginning from smear preparation through staining through biochemical testing procedures in order to identify these organisms all of the way to genus and species level?

Answer
hi diana
I assume these are bacteria cultures. The first thing you do streak the culture on a petri dish and isolate the bacteria into  the colonies. They must be separated before you can identify them. Then you Gram stain them. You then have separation and some information.  You know the characteristics of the colonies (color texture etc) From the stained slide you know the shape of the organism and whether it is gram + or gram - . Next you have to use  a differential media. Gram positives will require a different media then gram negatives,  Finally you will have to determine the biochemistry.  Gram negatives for example will ferment different sugars depending upon the species