Question

A student placed a disk of filter paper in each of the following solutions: disinfectant 1, disinfectant 2, disinfectant 3, and distilled water. While the four disks were soaking in their respective solutions, she streaked a sterile nutrient agar dish with a culture of E. coli bacteria. Then, she placed each disk carefully onto the nutrient agar dish, placed the lid on the dish, taped it shut, and incubated the dish at 37°C for several days. The diagram shows how the nutrient agar dish looked on Day 1 and Day 4. The shaded portion of the plate on day 4 indicates the bacterial growth. Look at the dishes in the diagram. Which disinfectant was the most effective at controlling the growth of E. coli?

Answer 1

The disinfectant that was the most effective at controlling the growth of E. coli is disinfectant 2 because of the least number of Ecoli strains found on the dish compared to the other disinfectants. Also dish 4 that cointains water has the most number of Ecoli strains because water is not a disinfectant and Acoi do not die in water alone.