What are the reasons for irreproducible results in cross-streak assay?

01 January 1970 0 5K Report

I did a cross-streak assay to test the antibacterial activity of the marine epiphytic bacteria against some fouling bacteria. The tests were done in two separate batches (different time but methods and culture conditions were standardized). The results showed that the number of susceptible fouling bacteria decreased in the second batch as compared to the first batch. Is there any reason for the irreproducible results(antibiotic resistance/ secondary metabolites not reproducible)? And does this matter since it is only the primary screening and qualitative test for antibacterial activity?

Thank you :-)

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