Antibiotic therapy

Parenteral antibiotics must be started as soon as the condition is suspected and before the results of the bacteriological examination are known.

Penicillin G has long been the antibiotic of choice for treating and preventing anaerobic infections2,19,23. It reduces morbidity and mortality in experimental gas gangrene. It has changed the fate of war injuries. Therefore, to this day, penicillin G on its own and in high doses remains active against Group A Streptococci and a large number of anaerobic bacteria (Clostridium, Fusobacterium and Peptostreptococcus)24. In adults, daily dosage is around 30 million units in the absence of contra-indications. Trauma and oedema restrict antibiotic penetration which is why high dosage is necessary.

Unfortunately more and more bacterial strains are becoming penicillin G-resistant (Bacteroides sp., Prevotella melaninogenica, etc.). This has led to changes in this long-standing regimen73-75. In present times more stable betalactams are being used, such as carboxypenicillins (ticarcilline), ureidopenicillins (piperacilline) . Alternatively penicillin G is being combined with imidazole derivatives (metronidazole, ornidazole). Cephalosporins - with the exception of cephamycin - are usually much less effective than penicillin. Rifampicin, chloramphenicol, macrolides (erythromycine) or clindamycine can be used on patients with an allergy to penicillin. Clindamycin is very often recommended by North american authors because of its anti-toxin activity76,77 but may be poorly tolerated and resistance is increasing so that its use has greatly decreased in Europe. Often glycopeptides and imipenem are preferred when there are contra-indications to penicillin.

Although Clostridia infections would seem to justify monotherapy by high doses of penicillin G, the clinical management requires greater distinction: Firtsly there is no clinical difference (apart from frequency in relation to location and aetiology) between clostridial infections and non-clostridial infections (i.e, infections caused by anaerobic Streptococci or Gram-negative bacilli, particularly Bacteroides sp.). However the latter are becoming increasingly penicillin G-resistant. This means that where stopping the infection is a matter of urgency empirical therapy should cover these organisms as well. Secondly, many of these infections also involve a number of other bacteria. Aerobic germs - usually Gram-negative bacilli -are often present, either ab initio or by superinfection. The involvement of Gram-negative bacilli (Enterobacteria, Pseudomonas, etc.) should not only be considered because of a possible superinfection, but also because the are synergistic in that the beta-lactamase they produce reduce the effectiveness

of penicillin on the anaerobes , , . Combining these drugs with a beta-lactamase inhibitor may be helpful.

A combination of piperacilline, imidazole derivates and aminoglycosides (so-called triple therapy) has often been recommended. Piperacilline and imidazole derivates against anaerobes, the aminoglycoside being added for the Gram-negatives4,28. Combinations of ticarcilline - clavulanic acid -aminoside, or piperacilline - tazobactam - aminoside, or imipenem as monotherapy are other possible combinations.

There is no fixed duration for the initial antibiotic therapy. It should be continued at least until general and local signs of infection have ceased. Most authors recommend an average three-week duration. Unless infectious complications appear in other locations (pneumopathy, septicaemia, etc.), or a superinfection occurs, the results of subsequent bacterial samples does not justify changing the initial antibiotic therapy.

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