If you want to limit your search to just few selected types in given index you could do that this way:
fos_elastica:
indexes:
app:
types:
article:
properties:
title: ~
desc: ~
# ....
news:
properties:
title: ~
desc: ~
# ....
$query = 'search-string';
$mngr = $this->get('fos_elastica.index_manager');
$search = $mngr->getIndex('app')->createSearch();
$search->addType('article');
$search->addType('news');
$resultSet = $search->search($query);
$transformer = $this->get('fos_elastica.elastica_to_model_transformer.collection.app');
$results = $transformer->transform($resultSet->getResults());