The present invention relates to characterizing changes in mammalian bacterial gastrointestinal, cutaneous and nasal microbiota associated with antibiotic treatment and various disease conditions (such as asthma, allergy, obesity, metabolic syndrome, gastrointestinal reflux disease (GERD), eosinophilic esophagitis, gastro-esophageal junction adenocarcinomas (GEJAC), infections due to bacteria that are resistant to antibiotics, including Methicillin-resistant Staphylococcus aureus (MRSA), Clostridium difficile, vancomycin-resistant enterococci, etc.) and related diagnostic and therapeutic methods. Therapeutic methods of the invention involve the use of live bacterial inoculants that are capable of restoring healthy mammalian bacterial gastrointestinal, skin, and nasal microbiota.