wildcat14

Hi everyone, I am trying to phase reverse Salmonella Locarno (z29:z42). The phase that I want is z29. I've already tried passing the bacterium through semisolid agar containing antiserum with z42. I've increased the concentration per pass. The little bugger is swimming fine, but when I test for both phases...phase 42 is still present. Any idea why this is? I'm surprised since z29 is the first phase, and I'm having a tough time getting it. Can anyone point me in the right direction?