Slick Slider: reload the slider

I have an issue about the Slick Slider i'm using in wordpress (GALLERY post format) It's working good when the page load, but i'm using an infinite scroll, so some posts are loaded with Ajax. My Ajax in isotope is:

$container.infinitescroll({
    navSelector  : '.pagination',
    nextSelector : '.pagination a', 
    itemSelector : '.post',
    loading: {
        msgText: 'Chargement des contenus...',
        finishedMsg: 'No more tiles to load.',
        img: 'http://ift.tt/1eAtFY4'
    }
},
    // call Isotope as a callback
    function( newElements ) {
        $container.isotope( 'appended', $(newElements));
    }
);

I'm trying to reload the Slick Slider in this function, but the slider is in my functions.php, following this tutorial: http://ift.tt/1Gfsprd

The slider are not reloaded when the next page (scroll) appears ... Do you know how I could reload the slider in the infinite scroll function or maybe in the functions.php ?

Thanks in advance for the help