Fig 3. UV-C light is germicidal to homemade E. coli biological indicators.

A. A homemade Escherichia coli (E. coli) Biological Indicator (BI) shown a on glass coverslip. B. Homemade E. coli BIs were incubated for 16 hrs in an orbital shaker. Conical on the left is a negative control (no E. coli on disk) and conical on the right is a positive control (E. coli on disk). C. Serial dilutions of E. coli on glass coverslips. The coverslips were incubated as described above and the Optical Density at 600 nm (OD₆₀₀) was measured. The mean and SEM are shown. Data are pooled from 3 separate experiments. D. Homemade BIs were exposed to discrete doses of UV-C (mJ/cm²) and then incubated as described above. OD₆₀₀ was measured and plotted. The mean and SEM are shown. Data are pooled from separate experiments (0 mJ/cm²: n = 4; 500 mJ/cm²: n = 6; all other doses: n = 7).