jquery ui autocomplete adding a span

It's for accessibility reason, blind people can 'read' how much results are find. If you really want to delete this, you can modify the source code:

this.liveRegion = $( "<span>", {
                role: "status",
                "aria-live": "polite"
            })
            .addClass( "ui-helper-hidden-accessible" )
            .insertAfter( this.element );

But it's not recommended.

I solved it by adding a CSS rule:

.ui-helper-hidden-accessible { display: none; }