Antimicrobial Therapy

Intensive surgical and medical therapy that includes the administration of intravenous fluids and management of septic shock are the hallmarks of treatment (55). Antimicrobial therapy is an essential element in the management of skin, soft tissue, and muscle infection. Establishing the bacterial etiology and the bacterial susceptibility initially by Gram stain, and later by culture, can allow for selection of proper antimicrobial therapy. Often, however, the initial therapy is empiric, based on epidemiological, historical, and clinical features.

In cases where streptococcal etiology is suspected, parenteral penicillin is used. If staphylococcal infection is suspected, or when no initial clue for etiology is available, a penicillinase-resistant penicillin (e.g., oxacillin) is given. Macrolides or vancomycin can be used in penicillin allergic individuals, and an aminoglycoside, or quinolone, or a third-generation cephalosporin (i.e., ceftazidime, cefepime) can be given when a gram-negative aerobe bacilli is suspected. Recently, there have been an increase in the isolation of methicillin-resistant S. aureus (MRSA). Patients with serious staphylococcal infections should therefore be initially started on agents active against MRSA until susceptibility results are available. Vancomycin, daptomycin, linezolid, tigecycline, and quinupristin/dalfopristin can be administered to treat these infections.

In infections that involve Clostridium spp., the combination of penicillin and clindamycin is recommended. This is based on in-vivo and in-vitro data of showing greater efficacy of the combination to each agent alone (56,57). Since many of the infections are polymicrobial aerobic-anaerobic in nature, coverage against these organisms is often necessary.

The gram-negative anaerobic bacilli, Prevotella spp., and Fusobacterium spp. previously susceptible to penicillins have been shown in the last decade to have increased rates of resistance to these and other antimicrobial agents. The production of the enzyme beta-lactamase is one of the main mechanisms of resistance to penicillins by many gram-negative anaerobic bacilli, including members of the B. fragilis group. Complete identification and testing for antimicrobial susceptibility and beta-lactamase production are therefore essential for the management of infections caused by these bacteria.

Antimicrobial therapy for mixed aerobic and anaerobic bacterial infections is required when polymicrobial infection is suspected (50). Antimicrobial agents that generally provide coverage for S. aureus as well as anaerobic bacteria include cefoxitin, clindamycin, carbapenem (i.e., imipenem, meropenem), and the combinations of a beta-lactamase inhibitor (i.e., tozobactam) and a penicillin (i.e., piperacillan) and the combination of metronidazole plus a beta-lactamase-resistant penicillin. Cefoxitin, the carbapenems, tigecycline, and a penicillin plus beta-lactamase inhibitor also provide coverage against Enterobacteriaceae. However, agents effective against these organisms (i.e., aminoglycosides, fourth-generation cephlosporins, and quinolones) should be added to the other agents when treating infections that include these bacteria.

Hyperbaric oxygen (HBO) therapy for clostridial myonecrosis is controversial (50). HBO increases the normal oxygen saturation in the infected wounds by a thousand fold, leading to a bacteriocidal effect, improved polymorphonuclear cells function, and enhanced wound healing (58). No controlled studies were done, and the published reports do not provide evidence of beneficial effect. The potential toxicity of HBO is also of concern. The most important limitation of utilizing HBO therapy is the lack of availability of appropriate hyperbaric chambers in most hospitals. Transportation of a seriously ill patient to a facility with a hyperbaric unit is hazardous, and the separation from immediate care for the unstable patient is risky. Transportation should not be done prior to extensive surgical debridement. However, the use of HBO should be considered when the involved tissue cannot be completely excised surgically, as may be the case in paraspinal or abdominal wall sites.

An additional mode of therapy is the negative pressure therapy or vacuum assisted closure. This is a very effective method of reducing bacterial load by removal of infected tissue debris and wound fluid (59).

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