i think you can PHP it using an if statement.. like so:
Say this is the loop.. (simple one i know):
<?php if ( have_posts() ) : while ( have_posts() ) : the_post(); ?>
<?php
$post_type = get_post_type_object( get_post_type($post) );
$post_type_name = $post_type->labels->singular_name
if ($post_type_name == 'example') {
echo '<div class="highlight searchResults">';
} else {
echo '<div>';
?>
<h3><?php the_title(); ?></h3>
<p><?php the_excerpt(); ?></p>
</div>
<?php endwhile; else: ?>
<p><?php _e('Sorry, no posts matched your criteria.'); ?></p>
<?php endif; ?>
.
Dont forget to change the ‘example’ with the singular name of the custom post type you are checking for in the search restuls…
Hope this helps 🙂