I have a mutation that is marked with spectinomycin resistance, I am transducing it into a different background and I am getting colonies (~10), in my no phage control. This has happened with 2 different recipient strains and two different genes marked with the same antibiotic resistance. I am using a spectinomycin concentration of 1000ug/mL. Has someone had the same problem? if so, how had you solved it?