The infection of a mammalian host by a microorganism can be prevented or treated through the administration of substrates for transglutaminases or antibodies against such substrates that inhibit the transglutaminase-mediated interaction of the microorganism with the mammalian host. These compounds may be used in the identification, prevention or treatment of microbial infection of mammalian hosts such as immunocompromised or immunosuppressed humans, for example, those having AIDS or undergoing transplantation or anti-cancer therapy.