Hi welcome to the health care magic Metronidazole group drug cover anaerobic bacteria more For covering gram positive organism also (which leads boil formation) it s better to prescribe ciprofloxacin like antibiotic as well For boil (if increased in size) incision and drainage can be done with local dressing for treatment For diarrhea maintain hydration with lots of water Avoid excess spicy foods and fatty meals Excess tea, coffee, smoking restricted If no improvement in diarrhea stool routine microscopic examination advisable Hope your concern solved Take care Consult physician for examination with keeping all this in mind