Did some research with screen-readers. I removed the focus from the first element and added the focus to the current active slide. The screen reader announces the details after making some minor changes.

http://jsfiddle.net/1x8w9c3n/12/

Made following changes in this version:
1. script updated for markup changes to make the focus goes through a flow. PrevButton - Slider&Contents - NextBtn - Controls.
2. Updated aria-labeledlby to aria-describedby for sliders and its respective controls.
3. Focus moved to current active slide.
4.Btw, left and right arrow key should work as long the focus is anywhere inside the whole slide.

Let me know your comments.