Patient-related risk factors suggesting need for antibiotics include Certain valvular heart disorders Immunosuppression Procedures with higher risk involve areas where bacterial seeding is likely: Mouth Gastrointestinal tract Respiratory tract Genitourinary tract In so-called clean (likely to be sterile) procedures, prophylaxis generally is beneficial only when prosthetic material or devices are being inserted or when the consequence of infection is known to be serious (eg, mediastinitis after coronary artery bypass grafting).