Question

When two bacterial strains are orally ingested, bacterium A has an ID50 of 10,000 and bacteria B has a ID50 of 10. However, when the bacteria are injected into a mouse model of infection, bacterium A (LD50 =10) is more virulent than bacterium B (LD50=10,000). Explain how these results might be possible

Answer 1

Answer.

ID₅₀- Amount of pathogenic microorganisms that will produce demonstrable infection in 50per cent of the test subjects.

(LD₅₀)- Amount of pathogenic microorganisms that will kill 50 per cent of the test subjects.

There is a huge difference in causing infection in 50% of test populaion and resulting into the death of the 50 % of test population. So here, in this case, the situation is possible because :

Although less number of B bacteria are required to cause the infection indicated by ID50 value which is 10 but large number of bacteria are required to cause the death of 50% population indicated by LD50 value of 10,000. This is because every infection is not resulting into the death of the test population.