Clarithromycin Biaxin Erythromycin Erythocin, Erythroped Roxithromycin Telithromycin Ketek Pneumonia Visual Disturbance, Liver Toxicity.[7] Spiramycin Rovamycine Mouth infections Fidaxomicin Dificid Treatment of Clostridioides (formerly Clostridium) difficile infection.[8] May be more narrow-spectrum than vancomycin, resulting in less bowel microbiota alteration.[9] Nausea (11%), vomiting, and abdominal pain.[10] Bactericidal in susceptible organisms such as C. difficile by inhibiting RNA polymerase, thereby inhibiting protein synthesis.[10] Monobactams Aztreonam Azactam Gram-negative bacteria Same mode of action as other beta-lactam antibiotics: disrupt the synthesis of the peptidoglycan layer of bacterial cell walls.