Infestations of bedbugs are bad news for homeowners, hotel chains and even movie theaters, but have generated booming business for American Textile Co., Duquesne, Pa., manufacturer of mattress, box spring and pillow protectors that are bedbug-proof. An estimated 35,000 stores nationwide carry the products, including Walmart, Bed Bath & Beyond and Macy’s, among others. American Textile has seen an 80 percent jump in sales since the blood-eating, noctural bedbug’s resurgence in the late 1990s, an indication that the child’s rhyme “good night, sleep tight, don’t let the bedbugs bite” is a new reality.