Is that CCK-8 test can also react with DH5a (E.coli)?

In numerous studies have shown that CCK-8 or MTT tests for detecting the proliferation of cancer cells incubated with certain bacteria. However, in my recent work, I find that DH5a also presents a great influence on the OD450 of the CCK-8 test. I really wonder the validity that using this method for examining the proliferation of co-culture bacteria and cancer cells. Furthermore, I apply Hematocyte Counter for checking this result, I find that the so-called phenomenon of cancer cells proliferation have been definitely disappeared, or even displayed cells number decreasing. I did not know how to explain these conflicting results.

Many thanks for your kindly response.