Periodic postprocedure follow-up is indicated to ensure resolution of the infection. At the Boston University student health service, CA-MRSA 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.
Incision and drainage technique reported. In one study, adult patients were treated with incision and drainage by a surgeon.8 The technique used a#11 blade applied in a “sawing motion” to create a wide opening. The wound cavity was explored for loculations and packed. The identical technique can be used in the office, with one caveat: This study included patients who had an abscess larger than 5 cm in diameter and some whose immune system was compromised—situations not managed routinely in the office.
Are antibiotics indicated after incision and drainage for MRSA?
In the same study,8 the cure rate with incision and drainage alone was just over 90%. The cure rate in the treatment arm of the study, in which patients also received an antibiotic, was 84% (the difference was statistically insignificant), and coverage was inadequate for MRSA. Treatment with cephalexin after incision and drainage resulted in one patient harmed for every 14 treated.
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, start the patient on trimethoprim (TMP)-sulfamethoxazole (SMX) or tetracycline if incision and drainage fail to promote healing of the MRSA lesion within 7 days. Clindamycin is an option, although resistance is increasingly common. Adjust the choice and dosage of antibiotic as needed once culture and susceptibility testing results are available.
TMP-SMX is generally well tolerated at the recommended dosage of one or two double-strength tablets (160 mg of TMP, 800 mg of SMX) twice daily for adults. If creatinine clearance is 15 to 30 mL/min, halve the dosage. The rate of sulfa allergy with TMP-SMX (3%) is similar to what is seen with other antibiotics.
Tetracycline’s dosing schedule—for adults, 250 or 500 mg, four times daily— makes it difficult to use. Gastrointestinal upset, phototoxicity, and hepatotoxicity can occur. The possibility of tooth discoloration precludes its use in children.
Clindamycin carries a high rate of gastrointestinal-related problems—Clostridium difficile infection in particular (10% incidence, regardless of 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 such resistance. The dosage typically is 150 to 300 mg, every 6 hours.
Doxycycline and minocycline are not recommended. Both carry a 21% failure rate.10
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 (pressor agents). Routine use in the community without infectious disease consultation is not advised.
For lesions that are neither fluctuant nor purulent
In such cases, appropriate first-line antibiotics are a semisynthetic penicillin (e.g., dicloxacillin), a first- or second-generation oral cephalosporin, a macrolide, and clindamycin.10 These antibiotics are preferable for group A streptococcal infections, erysipelas (which can be 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, although topical antibiotics can often be used for limited cases of impetigo.
CASE RESOLVED
Your patient, who meets criteria for a Class 2 CA-MRSA infection, undergoes incision and drainage of the lesion. No antibiotic is administered.
Two weeks of daily packing of the wound follow—again, without an antibiotic. Subsequently, the wound heals without sign of infection.
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, all staff members must wash hands with soap and water or an alcohol-based sanitizer. For the most part, MRSA remains susceptible to triclosan, a topical antiseptic in commercial hand soaps.
Clean equipment as needed with 10% sodium hypochlorite solution or another agent effective against MRSA. Surgical instruments should be disposable or sterilized after each use.
At the patient’s home. Instruct patients to clean the wound, wearing fresh disposable gloves each time, and to cover it with a new, dry dressing. Tell families to avoid sharing linens and clothing unless they have been washed in hot soap and water and dried in a heated dryer. MRSA can live for weeks or months on surfaces exposed to infected wounds11 ; these surfaces can be disinfected with a 10% solution of bleach.