Opportunistic infections. How is it that some microbe (say a bacteria) that has no virulence factors and doesn’t cause disease in a healthy individual all of the sudden do when said individual’s immune system is weak?

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Opportunistic infections. How is it that some microbe (say a bacteria) that has no virulence factors and doesn’t cause disease in a healthy individual all of the sudden do when said individual’s immune system is weak?

In: Biology

Many microbes are only harmless to us because they are quickly annihilated by a healthy immune system in normal circumstances. When that immune response is dampened, those microbes can take hold and cause illness that we wouldn’t experience otherwise.

Opportunistic infections often occur when all the nkrmal bacteria in your body is depleted. For example if you take an antibiotic, the antibiotic will target all bacteria. This includes normal flora (microbes are always in your body).

However, antibiotics wont kill all your bacteria. And since the normal flora from your body is gone, the opportunistic bacteria has no competition so it is able to outgrow your normal defenses.

Think about bacteria like sports fans after a big hometown win and security as the immune system. As long as your security (immune system) is functioning properly there shouldn’t be any issues. But if your immune system is suppressed by say Chemotherapy all of a sudden the stadium security is running with half the staff missing and the fans can get rowdy before security can respond.