Chronic Granulomatous Dz and H2O2

[MudPhud20XX]

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So CGD is basically the lack of NADPH oxidase which utilizes O2 to make hydroxyl radical and hydrogen peroxide, which are microbicidal.

Kaplan Immunology explains that

"If the patient is infected with a catalase negative organism, the H2O2 waste product produced by the bacterium can be used as a substrate for myeloperoxidase, and the bacterium is killed. If, however, the person is infected with a catalase-positive organism, the myeloperoxidase system lacks its substrate (b/c theses organims destory H2O2)."

So I get the idea that CGD patients suffer from catalase-positive organism, but the part that I don't understand is that the H2O2 being produced as a waste product by the bacterium. Why would the catalase negavie bacteria produce H2O2? What is the mechanism here? Also CGD patient don't have NADPH oxidase, so they can't really make H2O2 right?

 

[Myxedema]

Hydrogen peroxide production has nothing to do whether the bacterium is catalase positive or negative. Like it happens in the human cells, various processes can generate free oxygen radials, such as radiation and electrons skipping ETC and leaking into oxygen. Free radicals, in turn, can produce hydrogen peroxide. Now, if the bacterium has the catalase enzyme, it can degrade it to water and molecular oxygen (O2). If not, it can't.

 

[Transposony]

So I get the idea that CGD patients suffer from catalase-positive organism, but the part that I don't understand is that the H2O2 being produced as a waste product by the bacterium. Why would the catalase negavie bacteria produce H2O2? What is the mechanism here? Also CGD patient don't have NADPH oxidase, so they can't really make H2O2 right?

For board purpose, all living things makes H2O2 as a byproduct of cellular metabolism which is degraded by Catalase ( and other mechanisms).
In addition, H2O2 is specifically made by neutrophils/macrophages using NADPH oxidase to kill bacteria via respiratory burst.
Since CGD patient don't have NADPH oxidase and can't make their own H2O2. But they can utilize (catalase negative) bacterial H2O2 ( since they do have Myeloperoxidase) for respiratory burst and therefore make bleach to kill the bacteria inside the phagolysosome.
However, a catalase positive bacteria will neutralize it's own H2O2 inside the phagolysosome which cannot be used for respiratory burst and therefore to make bleach to kill the bacteria.
It is very well explained by Goljan in his audio.