Several management schemes have been proposed to guide the appropriate level of therapy based on presenting patient characteristics.6,7 If a lesion is clearly fluctuant, incise it and drain the fluid, or refer the patient for surgical consultation. If the lesion is not clearly fluctuant, needle aspiration may help to determine the need for more extensive incision and drainage or to collect a specimen for culture. Although culture of skin lesions may not have been routine in the past, the advent of CA-MRSA has made it so, particularly given that MRSA lesions may not be clinically distinguishable from those caused by nonresistant S aureus.
Periodic postprocedure follow-up is indicated to ensure resolution of the infection. At our health center, patients return every few days for an appointment with nursing staff for wound irrigation and packing change until the lesion visibly improves. Systemic effects from the infection are monitored, as well.
Adult patients in 1 study were treated with incision and drainage by a surgeon.8 The technique described in the article used an 11 blade and a “sawing motion,” creating a wide opening. The wound cavity was explored for loculations and packed. This technique is identical to that used in the office. There is one caveat, though: This study included abscesses larger than 5 cm and patients with compromised immune systems—situations not routinely managed in the primary care office.
Are antibiotics indicated after incision and drainage for MRSA? In this same study, cure rates with incision and drainage alone were just over 90%.8 The cure rate in the treatment arm also receiving an antibiotic was 84% (difference was not statistically significant), and coverage was inadequate for MRSA. Treatment with cephalexin after incision and drainage resulted in 1 patient harmed for every 14 treated (NNH=14). A pediatric study also showed that antibiotics do not affect the outcome of skin lesions following incision and drainage.5 When deciding whether to prescribe postprocedure antibiotics, keep in mind the need to avoid contributing further to bacterial resistance.
Generally if incision and drainage fail to promote healing of the MRSA lesion within 7 days, start the patient on trimethoprim-sulfamethoxazole or tetracycline. Clindamycin is an option, though resistance to it is becoming more common. Adjust the antibiotic choice as needed when culture and sensitivity results become available.
Trimethoprim-sulfamethoxazole is generally well tolerated at the recommended dose of 1 to 2 double-strength tablets (160 mg TMP, 800 mg SMX) twice daily for adults. If a patient’s creatinine clearance is 15 to 30 mL/min, reduce the dose by half. The rate of sulfa allergy is similar to other antibiotics, at 3%.
Tetracycline’s dosing schedule—for adults, 250 or 500 mg 4 times daily—makes it difficult to use. Gastrointestinal upset, phototoxicity, and hepatotoxicity can occur. The possibility of tooth discoloration precludes tetracycline’s use in children.
Clindamycin carries a high rate of gastrointestinal-related problems, Clostridium difficile infection in particular (10% incidence administered in any route). Inducible resistance to clindamycin is 50% in MRSA infections.9 Recent use of antibiotics may increase the likelihood of clindamycin resistance, with erythromycin in particular inducing this resistance. Its dosage typically is 150 to 300 mg every 6 hours.
Doxycycline and minocycline are not recommended, as they carry a 21% failure rate.9
Linezolid is costly and has many drug interactions. In particular, linezolid has the potential to cause serotonin syndrome with agents that affect the serotonergic system. Linezolid may also interact with medications that affect the adrenergic system (pressors). Its routine use in the community without infectious disease consultation is not advised.
For lesions that are not fluctuant or purulent, appropriate first-line antibiotics are semisynthetic penicillins (dicloxacillin), first- or second-generation oral cephalosporins, macrolides, and clindamycin.9 These antibiotics are preferable for group A streptococcal infections, erysipelas (which can be quite aggressive), and impetigo. Adjustments can be made as culture results become available or if the clinical response is inadequate. There is no particular utility in waiting to administer oral antibiotics in cases of erysipelas or impetigo, though topical antibiotics can often be used for limited cases of impetigo.
Prevention: Simple precautions are the rule
Most CA-MRSA infections result from direct contact with a patient’s wound or from wound drainage on environmental surfaces.
In the medical office. In addition to using sterile technique during incision and drainage, be sure that all staff members wash their hands with soap and water or with an alcohol-based sanitizer. For the most part, MRSA remains susceptible to triclosan, a topical antiseptic in commercially available hand soaps.