A urine sample with more than 100,000 organisms is considered indicative of infection. A urine sample containing 5,000 bacteria, with a generation time of 30 minutes, sits for 3 hours before finally being assayed. How many bacteria will then be present within the sample?

320 000

Explanation:

The generation time G is the time it takes a bacterial population to double.

If N₀ is the number of bacteria at the beginning of the experiment and N is the number at any time t,

N = Nₒ * 2ⁿ

where n is the number of generations

n = t/G

dа ta:

N₀ = 5000

G = 30 min

t = 3 h

Calculations:

t = 3 h = 180 min

n = 180 min/30 min = 6

N = 5000 * 2⁶ = 5000 * 64 = 320 000

There will be 320 000 bacteria in the sample.