Antibiotic prophylaxis

Editor, – Recommended prophylaxis of endocarditis was clarified by the letter from Dr I. Hewson and response by B. Khariwala ('Letters' Aust Prescr 1997;20:57-8).

Antibiotic guidelines' 9th Edition 1996 makes no reference to prophylaxis for in situ implants other than cardiac valves. Prophylaxis is recommended at the time of insertions on pages 161 (orthopaedic), 162 (neurosurgery)and 164 (head, neck, thoracic). The dire results of established infection are briefly mentioned on pages 33 (intravascular) and 148 (orthopaedic).

Recent enquiry, precipitated by my wife's knee replacement, revealed my dentist uses amoxycillin 3 g, but an orthopaedic surgeon uses cephalosporin or flucloxacillin because the organism is more likely to be staphylococcus than a streptococcus.

Discussion with the physician associated with my wife's orthopaedic surgeon suggests amoxycillin may still be appropriate for oral procedures, but for urinary and colonic manipulations, gram negative organisms demand gentamicin.

L.K. Morgan
General Practitioner
Bendigo, Vic.

Benafsha Khariwala, the Managing Editor of Therapeutic Guidelines Ltd, comments:
Any patient with a joint prosthesis is at a small risk of infection of the prosthesis by the haematogenous route. Early recognition and treatment of infection at any site is important to prevent seeding of the prosthesis. The value of antibiotic prophylaxis has not been established for procedures in which bacteraemia is likely to occur e.g. dental surgery, cystoscopy and surgical procedures on infected tissues.

However, antibiotic prophylaxis may be considered for patients at potentially increased risk of haematogenous infection of joint prostheses, such as the immuno compromised and patients with insulin-dependent diabetes, when undergoing procedures with a high incidence of bacteraemia e.g. dental extractions or surgical procedures involving incisions of the oral or gingival mucosa.