Termites generally attack solid wood and leave bark mulch alone because it doesn't provide a suitable place to live or hide. However, it sounds as though the mulch you're using has wood chips in it, so it could attract termites. Be certain to keep the mulch from directly touching siding or wood walls where termites would like to dine. The mulch can act as a convenient cover for them to move through to get to a meal. Keep the mulch 6-12 inches away from any wood structures on the home. If termites cross the wood-free zone, you'll be able to see the protective soil tubes they build. That will allow you to treat them before they become established in your home.