Question

Ten people are stuck in an elevator with a clumsy microbiologist who drops and breaks a vial containing 2 mL’s of a dangerous bacterium at a concentration of 1.1 X 107 cells per mL in the middle of the elevator. When the vial breaks half of the sample aerosolizes equally in 360 degrees and everyone inhales and equal amount of all bacteria released. The ID 50 of this organism is 5 X 105 cells and the LD 50 is 1X10 6. How many of these people will potentially get sick and how many could die? Explain the logic behind your answer.

Answer 1

5 people would get sick. Everyone can potentially die if no treatment received.

Step-by-step explanation:

"Vial breaks half of the sample aerosolizes equally in 360 degrees and everyone inhales and equal amount of all bacteria released"

1.1 x 10^7 / 2 = 5.5 x 10^6 bacteria in the air.

"Vial breaks half of the sample aerosolizes equally in 360 degrees and everyone inhales and equal amount of all bacteria released"

There 10 people in the elevator.

5.5 x 10^6 / 10 = 5.5 x 10^5.

Since the infectious dose treshold that make half of the population sick (ID50) is 5 x 10^5, we can assume everyone inhaled 5.5 x 10^5 bacteria and randomly 5 of them can get sick because of the bacteria.

No one would die "instantly" in the elevator because 5.5 x 10^5 is almost 10 times below the LD50 treshold which is 1 x 10^6 but there is a catch. Since bacteria can continue to grow and in every growth cycle bacteria doubles there is not much time left for those people. Lets assume doubling time of this bacteria is 20 minutes. Lets also assume it has lag phase 20 minutes. It would take bacteria 40 minutes to kill 5 of these people (2x5.5x10^5 = 1.1 x 10^6) since the amount of the bacteria reaches over LD50 treshold which is 1 x 10^6. Lets also assume bacteria continue to grow, risk of their death increases as the bacteria doubles so they can all eventually die from this bacteria.