Cutaneous Abscess - Etiology, pathophysiology, symptoms, signs, diagnosis & prognosis from the Merck Manuals - Medical Professional Version. Not Found Locations. View Consumer Version Written in everyday language. Professional Version. Merck Manual Professional Version × MERCK. Surgery of the anal fistula to drain an abscess treats the fistula and reduces likelihood of its recurrence and the need for repeated consideration should be given to possibility of strep species as cause that are still sensitive to traditional anti-staphylococcus agents such as dicloxacillin or cephalexin in patients able to tolerate penicillin. Antibiotic . Flucloxacillin is more appropriate than simple penicillin as it treats both Staphylococcus (staph) and strep. If the laboratory has confirmed streptococcal infection, then the most appropriate antibiotic is usually penicillin. All streptococci in the Lancefield group are very sensitive to penicillin. Those patients with penicillin allergy may.