The only way to do this is to edit the core template’s PHP file. Here’s how:
Open this file:
Add this code where you would like the categories to be shown:
$entry->getCategoryBlock( array('separator' => ', ', 'before' => '<span>', 'after' => '</span>') );
SAve and upload overwriting the original file.
You may also have to add it to the following file depending on your configuration:
Hope that helps.