I am not sure what strain it is. We had a milk culture done in early Dec. and they just told me it was bacterial and put me on antibiotics. They had me come back in for another culture last Friday and now they tell me it has e coli. It was done with a large q-tip that was wrapped in plastic. She took it out with gloves and squeezed fresh milk onto the tip. Then it was put in a long glass jar. From there, I don't know what happened but considering it was the second test done, I know there is something going on.