A stationary broth culture contains 10 billion (1010) cells. The microbial death rate during autoclaving of this spent culture is 1.5 minutes. How long must it be autoclaved to be considered sterile?
A) 16.5 minutes
B) 10 minutes
C) 20 minutes
D) 12 minutes
E) 9 minutes

Question

Quizplus · Accepted Answer

To achieve sterility, the number of surviving cells must be reduced to less than 1. Starting with 10 billion cells, it takes 1.5 minutes to reduce the population by one log (factor of 10). Therefore, it takes 1.5 minutes x 10 logs = 15 minutes to reduce to 1 cell, and an additional 1.5 minutes to ensure sterility, totaling 16.5 minutes.

A Stationary Broth Culture Contains 10 Billion (1010) Cells