Size of PowerPoint background

Hello, I have a problem with background picture dimensions. I made an picture 720x540. On this picture You have one pixel black lines. When i put it to PowerPoint and publish in Articulate the lines became blurry. I locked a size of presentation. I want this line sharp as in orginal picture, sharpy (exaclty 1px) not blurry.

What I have to do? See my file.

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