Load only admin bar translation on WordPress frontend

gistfile1.php

/**
 * Set en_US lang code if not in admin.
 */
function md_set_en_us_locale( $locale ) {
	if ( ! is_admin() ) {
		if ( ! defined( 'MD_REAL_LANG' ) )
			define( 'MD_REAL_LANG', $locale );
		$locale = 'en_US';
	}

	return $locale;
}
add_filter( 'locale', 'md_set_en_us_locale', 1 );

/**
 * Set real lang code.
 */
function md_set_real_locale( $locale ) {
	if ( defined( 'MD_REAL_LANG' ) )
		$locale = MD_REAL_LANG;

	return $locale;
}

/**
 * Load translations for admin bar.
 *
 * This loads only deafult (ie. core WP) translations,
 * it's possible to load plugins & themes translations
 * but that requeries more code.
 */
function md_load_translations() {
	unload_textdomain( 'default' );
	add_filter( 'locale', 'md_set_real_locale', 2 );
	load_default_textdomain();
}
add_action( 'admin_bar_init', 'md_load_translations', 1 );
add_action( 'wp_before_admin_bar_render', 'md_load_translations', 1 );

/**
 * Unload translations after admin bar
 */
function md_unload_translations() {
	unload_textdomain( 'default' );
	remove_filter( 'locale', 'md_set_real_locale', 2 );
	load_default_textdomain();
}
add_action( 'wp_after_admin_bar_render', 'md_unload_translations', 1000 );