eMedicine - The Role of Antibiotics in Cutaneous Surgery : Article by Elizabeth Billingsley

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The Role of Antibiotics in Cutaneous Surgery

Article Last Updated: Oct 14, 2006

The use of prophylactic antibiotics in patients undergoing dermatologic surgery has been an unclear and occasionally controversial topic, with few guidelines available in the literature.

The most common settings for the use of antimicrobials in cutaneous surgery include the following: (1) the prevention of a wound infection, (2) the treatment of a wound infection, and (3) the prevention of endocarditis.

To more clearly understand the role of antibiotics in skin surgery, knowledge of the skin flora, as well as the mechanisms of infection, is important. Resident and transient bacteria populate the skin. Resident florae consist of organisms on the skin that are relatively stable in number and composition. These bacteria vary among locations on the body and among individuals. Resident bacteria live on the stratum corneum and in the outermost layers of the epidermis. Transient flora lie on the surface of the skin, are derived from exogenous sources, and vary widely.

Coagulase-negative staphylococci, such as Staphylococcus epidermidis, are the most common organisms in the normal flora. These bacteria are not common pathogens in wound infections, but they have been implicated in some cases of endocarditis. Staphylococcus aureus, which is coagulase positive, is usually not among the resident flora, but it can occasionally be found in intertriginous areas and in the nares (in 20-40% of patients). Certain cutaneous conditions, such as psoriasis and atopic dermatitis, and the use of retinoids can be associated with high skin counts of S aureus. S aureus is frequently isolated in wound infections and rarely causes endocarditis. Streptococcus viridans is common in the oral cavity, it can cause wound infections, and it has been isolated in endocarditis.

Bacterial flora varies in different anatomic sites. The head, neck, and upper part of the trunk have more sebaceous glands; therefore, more lipophilic organisms, such as Propionibacterium species, are found there. Exposed areas, such as the face, neck, and hands, have higher total numbers of bacteria, including more transient bacteria such as group A streptococci. Intertriginous areas, such as the axillae and groin, can be more heavily colonized with gram-negative rods, coryneforms, and S aureus. Pseudomonas aeruginosa frequently colonizes the external auditory canal and may cause infection of surgical wounds of the ear, as well as chondritis.

Factors such as sex; age; occupation; and exposure to soaps, disinfectants, medications, and ultraviolet light can modify the types and number of bacteria on the skin. The climate affects bacterial flora because temperature and humidity increase bacterial counts. Although good surgical preparation can eliminate transient flora and reduce resident flora to a minimum, complete sterilization of the skin is impossible. Approximately 20% of resident flora remains in the pilosebaceous units after antiseptic scrubbing.

For excellent patient education resources, visit eMedicine's Public Health Center. Also, see eMedicine's patient education article Antibiotics.

Wound infections occur when an organism has the opportunity to proliferate in tissue and the body's defenses cannot combat the organism or its proliferation. Certain patient characteristics can be associated with a higher incidence of wound infection; these characteristics include old age, chronic immunosuppression, diabetes mellitus, corticosteroid use, obesity, anergy, malnutrition, and chronic renal failure.

Bacteria can be introduced into a wound at the time of surgery if sterile technique is broken, or they can be introduced through airborne transmission of desquamated skin cells, aerosolized water droplets, or dust particles. A resultant wound infection may be more likely in patients who have S aureus colonization due to other cutaneous conditions or in patients or members of the surgical staff who are a nasal carrier of S aureus.

Infection rates increase with lengthy procedures and in certain body locations (eg, axillae, oronasal area). One study demonstrated that in patients undergoing Mohs surgery, the rate of wound infection is increased in those with large defects and in those undergoing procedures performed on the ears. The rate of wound infection is higher when hair at the surgical site is shaved rather than trimmed or left unshaven.

Infecting organisms are often part of the resident florae of the skin or nearby mucous membranes. S aureus is most commonly isolated in cutaneous wound infections; however, Escherichia coli and Streptococcus, Pseudomonas, and Proteus species may also be responsible. Occasionally, other gram-negative organisms and Candida albicans can be isolated; these may be associated with poor hand washing and improper wound care techniques. Inadequate postoperative wound care and poor hygiene can introduce bacteria into a wound, which can lead to infection.

Postoperative infections can occur as a result of poor surgical technique. For example, an improperly designed flap or a wound closed under too much tension may lead to ischemia, which can increase the risk of infection. Similarly, excessive suture material in a wound may increase this risk.

Postoperative hematoma formation and devitalized tissue from excessive cautery during surgery provide environments that promote bacterial growth.

Although the infection rate in cutaneous surgery is low and infection can usually be managed successfully with good results, in certain situations antibiotics may be prescribed preoperatively to prevent wound infection.

When the risk of infection is increased, as in patients undergoing surgery at certain body locations (eg, mouth, groin, axillae) and in those with chronic immunosuppression, S aureus colonization, or malnutrition, prophylactic antibiotics should be considered. The decision to prescribe prophylactic antibiotics should be based on the risk factors of the patient, the type and location of the surgery, and the risk that infection can lead to significant morbidity in that specific patient.

If bacterial infection is present at the surgical site, or even at a distal site, the infection should be treated before an elective procedure is performed, if possible. Distant respiratory tract, urinary tract, and skin infections can seed surgical wounds. This is likely caused by infection-mediated transient bacteremia that colonizes the surgical wound.

The prescribed antimicrobial agent should be targeted toward the most likely infecting organism, usually Staphylococcus and Streptococcus species. These organisms are also isolated most frequently in patients with endocarditis.

First-generation cephalosporins (cephalexin) and semisynthetic penicillinase-resistant penicillins (dicloxacillin) are the most commonly used prophylactic agents in skin surgery and skin infections because of their broad-spectrum coverage against most gram-positive cocci, E coli, Klebsiella species, and Proteus mirabilis. One to 2 g/d in divided doses is usually effective.

Clindamycin and erythromycin are effective alternatives for S aureus coverage in patients with an allergy to penicillin. Clindamycin has excellent tissue penetration, has a broad antimicrobial spectrum, and can be useful for wounds in the oral mucosa. S aureus resistance to erythromycin has been increasing, and it has better gastrointestinal tolerance because of its slow absorption.

Azithromycin, an azalide in a subclass of the macrolide antibiotics, provides good gram-positive coverage and a broad spectrum of activity against anaerobes and gram-negative bacteria. Azithromycin demonstrates cross-resistance with erythromycin-resistant gram-positive strains.

Trimethoprim-sulfamethoxazole has an identical antimicrobial spectrum to the third-generation cephalosporins, along with excellent coverage against gram-positive cocci. It may be a good agent to consider, especially in inguinal and perineal areas, but it is not effective when Pseudomonas species are a concern.

The quinolones are bactericidal antibiotics that have excellent bioavailability. The 4 generations of quinolones have increasing gram-positive coverage. Ciprofloxacin, a second-generation quinolone, has moderate S aureus effectiveness but excellent activity against pseudomonal organisms.

Vancomycin is intravenously administered and used when methicillin-resistant Staphylococcus or Enterococcus species or S epidermidis is of concern. Coagulase-negative Staphylococcus organisms are of concern in patients with recently implanted heart valves (<60 d), and intravenous vancomycin may be needed in these patients if they undergo cutaneous surgery.

Ideally, a prophylactic antimicrobial is orally administered 1-2 hours prior to the surgical procedure to allow tissue distribution and incorporation into the wound coagulum. Once a coagulum has formed in the wound, it is difficult for the antibiotic to penetrate and act effectively against trapped bacteria. Postoperative administration of the antimicrobial is usually unnecessary; however, many surgeons administer a second dose 6 hours later if surgery is delayed or prolonged or if significant breaks in sterile technique occur. No evidence suggests that coverage must be extended beyond 24 hours when it is initiated preoperatively.

In some clinical situations, the issue of prophylactic antibiotics may not be addressed preoperatively, but the surgeon may be concerned that the risk of infection is increased. Antibiotics are initiated immediately after surgery and continued for 3-7 days. To the author's knowledge, no reliable studies of an optimal duration of treatment or effectiveness of this approach are reported in the literature.

Griego and Zitelli published a report of their study of the use of intraincisional nafcillin to prevent wound infection. Patients undergoing Mohs surgery or dermatologic surgery received a solution of nafcillin sodium in the buffered lidocaine used for local anesthesia. The authors reported an infection rate of 0.2%, compared with 2.5% in control subjects who received standard buffered lidocaine. The reported advantage of the added nafcillin is the immediate achievement of effective levels of antibiotic in the tissue, along with decreased systemic exposure to the antibiotic (thus resulting in less toxicity and possibly decreased bacterial resistance). A follow-up study used intraincisional clindamycin as an alternative for penicillin-allergic patients and demonstrated similar efficacy.

The role of topical ointment in cutaneous surgery is to facilitate wound healing by keeping the wound moist and by increasing the removal of debris. As a result, any topical ointment (eg, petrolatum, topical antibiotic) is sufficient for postoperative use. Advantages to the use of petrolatum are that it is inexpensive and that it is less likely to cause allergic contact dermatitis and less likely to promote bacterial antibiotic resistance. In addition, because most excisional wounds are thought to become inoculated at the time of surgery, little theoretical benefit is achieved if topical antibiotics are applied to a layered closure.

Dermatologic operations are usually considered to be class 1 (ie, clean procedures) or class 2 (ie, clean-contaminated procedures), they are usually of short duration, and they are associated with a low risk of infection. The incidence of postoperative wound infections in cutaneous surgery, including Mohs micrographic surgery, is estimated to be less than 5% and may be closer to 1-2%.

Unfortunately, most data collected to determine the rates do not clearly distinguish between patients who received prophylactic antibiotics and patients who did not. However, in one study, the investigators evaluated the postoperative use of topical bacitracin compared with white petrolatum and found no significant difference in the overall rate of postprocedure infections between the 2 agents. In addition, no differences were observed in healing between the groups.

The clinical signs of a wound infection include edema, erythema, warmth, and purulence, which usually appear 4-8 days after a procedure. Infection should be considered when these signs are noted at the time of suture removal or if a patient calls and describes them. While some postoperative erythema and edema is not uncommon in a normally healing wound, these signs should improve with time. Worsening erythema and edema, and especially warmth with purulence, suggest infection. Reactivity to the suture material or allergic or irritant contact dermatitis due to a wound dressing or topical antibiotic can mimic these signs.

In patients with a presumed postoperative wound infection, a culture should be obtained and empiric antibiotic therapy should be initiated, with the realization that the most common organism isolated in cutaneous wound infections is S aureus. The proper technique for culturing a suspected wound infection is to roll the tip of the culture swab in a zig-zag fashion along the length of the incision after debriding any dead eschar from the wound. A first-generation cephalosporin (eg, cephalexin) or dicloxacillin provides good coverage against Staphylococcus and Streptococcus organisms. In patients with a penicillin allergy, clindamycin, azithromycin, and erythromycin are alternate choices. When culture and sensitivity results become available, the antibiotic can be changed to optimize treatment. When the presence or source of an infection is questionable, waiting for Gram stain or preliminary culture results may be advisable before therapy is started.

Pseudomonas infection of the ear must be recognized early, and therapy should be initiated upon any suggestion of infection. Pseudomonas chondritis infection manifests as a swollen painful ear and may progress to significant morbidity if treatment is delayed or inadequate. Oral ciprofloxacin and norfloxacin are good antimicrobial choices for treating Pseudomonas infection. Obtaining a culture of the ear is important because Staphylococcus, Streptococcus, and Proteus species may be other causative organisms and may require different antibiotic therapy.

Few guidelines are available regarding the use of prophylactic antibiotics for the prevention of endocarditis in patients undergoing cutaneous surgery. Endocarditis occurs when blood-borne bacteria lodge on damaged or abnormal heart valves, on the endocardium, or on the endothelium of anatomic cardiac defects. Endocarditis is associated with substantial morbidity and mortality rates.

Bacteremia can spontaneously occur, or it may be associated with a localized infection that can produce blood-borne bacteria. Invasive procedures, especially those involving the mucosa or contaminated tissue, may lead to transient bacteremia. Many physicians believe that antibiotic prophylaxis prior to procedures that may produce transient bacteremia can prevent endocarditis in patients at risk. Transient bacteremias can also result from normal daily activities, such as tooth brushing and chewing.

Although bacteremia may be common after many invasive procedures, only a limited number of species of bacteria commonly cause endocarditis. The organisms most frequently responsible for endocarditis are Streptococcus species, S aureus, and S epidermidis. Enterococcus species, gram-negative bacilli, diphtheroids, and even fungi may also be isolated. A physician must decide whether prophylactic antibiotics are needed on the basis of the risk level of the patient and the risk of the procedure performed. Potential adverse reactions to prophylactic antibiotics and cost-benefit aspects must also be considered to avoid the overuse of antimicrobial agents.

In 1997, the American Heart Association (AHA) published new recommendations for the prevention of bacterial endocarditis. These recommendations are an update from the 1990 guidelines and emphasize that most cases of endocarditis are not attributable to an invasive procedure. The underlying cardiac conditions of concern are classified into high risk, moderate risk, and negligible risk groups based on the potential outcome if endocarditis develops. Patients considered to be at high risk are those with prosthetic heart valves, those with a history of endocarditis, and those with complex cyanotic congenital heart disease. The moderate risk category includes patients with acquired valvular dysfunction and those with hypertrophic cardiomyopathy.

The new recommendations also more clearly define specific procedures for which prophylactic antibiotics are recommended. In the past, whether antibiotics were indicated in endocarditis prophylaxis for patients undergoing cutaneous procedures was unclear. The new guidelines specifically state that antibiotics are not needed in invasive procedures involving surgically scrubbed skin because bacteremia is unlikely. Most biopsies and excisions performed in a dermatology practice are in this category; however, when the skin is infected or colonized or when mucosal surfaces are involved, the use of antibiotics may be indicated in high-risk patients. No specific mention is made regarding Mohs surgery (which can be a lengthy procedure), hair transplantation, skin resurfacing, or other cutaneous procedures. Transient bacteremias occur at the time of surgical incision. If the operative area is surgically scrubbed, the risk of introducing bacteria into the bloodstream should be minimized.

Endocarditis prophylaxis is most effective when antimicrobials are perioperatively administered in doses that result in adequate antibiotic concentrations in the serum during and after the procedure. The antibiotic should be administered shortly before the procedure, and it should not be continued for an extended period after the procedure to reduce the likelihood of microbial resistance. Currently, the AHA recommends a single preoperative dose. The physician must decide which antimicrobial to administer on the basis of the bacteria likely to be present.

In summary, according to the new AHA guidelines, prophylactic antibiotics are not indicated in patients with cardiac abnormalities who are undergoing standard cutaneous surgery. Antibiotics are indicated for operations involving clinically infected lesions in high-risk patients, such as patients with prosthetic valves, patients with a history of endocarditis, and those with complex cyanotic congenital heart disease.

Prophylactic antibiotics should be used when procedures are performed on mucosal surfaces and considered in patients with Staphylococcus colonization and in patients with distant wound infections. Antibiotics can be considered in lengthy procedures (eg, Mohs surgery), especially in patients with prosthetic heart valves. Because Staphylococcus and Streptococcus species are the most likely pathogens, a first-generation cephalosporin, a semisynthetic penicillinase-resistant penicillin (eg, dicloxacillin), and clindamycin are all good choices.

A study by Sabetta and Zitelli revealed a 2.8% incidence of transient bacteremia in patients undergoing surgery on eroded but not clinically infected skin. They recommended that 1-2 g of a first-generation cephalosporin or dicloxacillin be administered 1-2 hours before surgery and continued for 1-2 doses in patients with prosthetic heart valves who undergo surgery on eroded skin. Physicians must weigh the risks and benefits when considering the use of antibiotics in these and other clinical situations.

No data in the literature supports the use of prophylactic antibiotics in patients with artificial joints who undergo cutaneous surgery. Patients with prosthetic joints usually do not require antimicrobial prophylaxis when undergoing gastrointestinal, genitourinary, or dental procedures. Most infections of indwelling prosthetic joints arise from contamination at the time of their insertion or from contiguous infection; however, an orthopedic surgeon may request that prophylactic antibiotics be administered to a patient who has undergone joint replacement or other orthopedic procedures in the recent past or if surgery is performed in an infected area. In this last situation, the patient's surgeon should be contacted prior to surgery. If the orthopedic surgeon is not available, antibiotic prophylaxis should be administered to those patients who are undergoing surgery on infected or abscessed skin or if the patient has a distant wound infection.

Some authors recommend the use of antimicrobial prophylaxis in patients with vascular prostheses who undergo genitourinary, dental, or other procedures. Others, however, do not believe that prophylaxis is necessary in patients undergoing dermatologic surgery if their grafts have been in place for more than 1 month. The patient's vascular surgeon can be consulted prior to surgery.

The Role of Antibiotics in Cutaneous Surgery

AUTHOR AND EDITOR INFORMATION

INTRODUCTION

PREVENTION OF WOUND INFECTIONS

ANTIMICROBIAL AGENTS

TREATMENT OF WOUND INFECTIONS

ENDOCARDITIS

CONCLUSION

REFERENCES