Surgery and Radiology Section

ANTIBIOTICS AND ANTIBACTERIALS

Topical antimicrobials and Antibiotics

• Antimicrobial agents and antibiotics eliminate or reduce the number of microorganisms in a wound that destroy tissue.
• Topical rather than systemic antibiotics are preferred for open wounds.
• Combined topical and systemic antibiotic therapy is advantageous in heavily contaminated wounds but not in mild or moderately contaminated wounds.
• Antibiotics applied within 1-3 hrs of contamination often prevent infection. Benefits of topical drugs should outweigh their cytotoxic effects.
• Antibiotics used effectively as topical ointments or added to lavage solutions are penicillin, ampicillin, tetracycline, kanamycin, neomycin, bacitracin, polymyxin, and cephalosporins.
• Once infection is established, topical and systemic antibiotics have no beneficial effect in preventing suppuration of wounds undergoing closure.
• Wound coagulum prevents topical antibiotics from reaching effective levels in tissues deep in the wound and also prevents systemic antibiotics from reaching superficial bacteria. These wounds must be debrided to allow antimicrobial access to bacteria.
• Topical steroids may inhibit epithelialization, wound contraction, and angiogenesis. Production of exuberant granulation tissue may be reduced by the one or two application of corticosteroids. Topical anesthetics may be used to reduce traumatic and postoperative pain.
• In wound management topical antibiotics have got both advantages and disadvantages compared to antiseptics

Advantages

• Selective bacterial toxicity, efficacy in the presence of organic material, and combined efficacy with systemic antibiotics.

Disadvantages

• Expense, narrower antimicrobial spectrum, potential for bacterial resistance, creation of “super infections”, systemic or local toxicity, hypersensitivity, and increased nosocomial infections.

1. Triple antibiotic ointment: Triple antibiotic ointment consists of bacitracin, neomycin, and polymyxin and is effective against a broad spectrum of pathogenic bacteria commonly infecting superficial skin wounds. It is more effective for preventing infection than for treating them.

2. Silver sulfadiazine: It is a 1% water miscible cream and is effective against most  of the gram-positive , gram-negative bacteria and fungi. It also serves as an antimicrobial barrier, can penetrate necrotic tissue, and enhances wound epithelialization. It is the drug of choice to treat burn wounds. 

3. Nitrofurazone: Nitrofurazone (Furacin) has broad spectrum antibacterial and hydrophilic properties, the later enabling it to draw body fluid from wound tissue, which helps  to dilute tenacious exudates so they can be absorbed into bandages. It delays wound epithelialization and loses some of its antimicrobial effects in the presence of organic matter.

4. Gentamicin sulfate: It is available as a 1% ointment or powder (Garamycin), but solutions are preferred. It is especially effective in controlling gram-negative bacterial growth (Pseudomonas spp., Escherichia coli, Proteous organisms). It is often used for wounds that do not responded to triple antibiotic ointment.

5. Cefazolin: Cefazolin is effective against gram-positive and some gram-negative organisms. Topically administered cefazolin is 95% bioavilable and rapidly absorbed; therefore systemic levels equal wound fluid levels within 1 hour.

6. Mafenide: Mafenide (hydrochloride or acetate) is a topical sulfa compound available as an aqueous spray. It has a spectrum against gram-negative bacteria, including Pseudomonas and Clostridium, and is particularly useful on severely contaminated wounds.