Isolating different bacteria.

Question

How do you isolate Staph. aureus, Staph. epidermidis, and Enterococcus faecalis? I know what I have to do to identify them but I don't know how to separate them into three pure cultures. Please help

Answer 1

Each strain grows on specific medium and might have specific antibiotic resistance gene. You can find that out from literature and get agar plates with those specific antibiotics each. Only the strain with antibiotic resistance gene would grow, other would not. Pick up single colonies from plate, culture in right medium with an antibiotic, make a negative control with no colony and if that is clear then you analyze DNA from other culture tubes. The one that shows right pattern on DNA analysis, you grow that as single culture. 

 

Yourepeat the same process until you have established pure lines.