The epidemiology of pediatric community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) has been explored in many investigations, but questions remain regarding the management of this infection. MRSA is an increasingly common community-acquired pathogen in pediatric populations. 1–3 Sattler et al. 1 found no significant differences in the exposure to risk factors (antibiotic exposure, prior hospitalizations, health care visits, day-care, health care worker or nursing home resident exposure and presence of any underlying illness) in children with CA-MRSA than in those with community-acquired methicillin-susceptible Staphylococcus aureus infection; in addition no significant risk factors for CA-MRSA were identified among household contacts. Other investigators have also demonstrated that CA-MRSA infections are no longer confined to children with previously established risk factors. 1
Incision and drainage, without the use of adjuvant antibiotics, is generally effective therapy for skin and soft tissue abscesses in otherwise healthy patients. This has not been established for CA-MRSA infections. 4, 5 Some investigators have reported that MRSA bacteremia is associated with a significantly increased attributable mortality compared with methicillin-susceptible S. aureus bacteremia, whereas others have reported that methicillin resistance does not influence the outcome of S. aureus bacteremia. 6–8
We present a prospective observational study on the management and outcome of skin and soft tissue abscesses caused by CA-MRSA in children.
This was a prospective observational study approved by The University of Texas Southwestern Medical Center Institutional Review Board and Children’s Medical Center of Dallas Research Advisory Committee. Informed consent of parents was not required. For the purpose of this study, CA-MRSA disease is defined as MRSA infection in a child presenting from the general community, without regard to presence or absence of MRSA risk factors.
Children presenting to the emergency department or acute care clinic of Children’s Medical Center, Dallas, TX for management of skin and soft tissue abscesses caused by MRSA were identified when their culture results became available and then followed prospectively. Children were initially identified from the microbiology laboratory log book in the Emergency Department or Acute Care Clinic on a Monday through Friday basis. Patients were identified by a faculty study physician from May 13, 2002 to February 10, 2003, with the exception of August 26 to September 22, November 18 to December 15 and December 23 to January 5 when this physician had other duties. Patients were not included if a working phone number was unavailable at the time of identification or if there was inadequate documentation from the initial evaluation. There were no exclusion criteria. Data were collected by the faculty study physician from the subjects’ initial evaluation (retrospective) and at follow-ups at 1 to 6 days (generally when culture and susceptibility data became available, prospective) and at 6 to10 days (generally 1 week after the first follow-up, prospective). Follow-up was by return visit to clinic facilities or by telephone call to an adult care giver by a physician responsible for the care of the patient.
Data collection included patient demographics, past medical history, abscess incision and drainage, wound packing, abscess culture results, antibiotic therapy before culture results, changes in antibiotic therapy with culture results, fever (≥101°F), site and size (initial evaluation: diameter of total infected area as determined visually; follow-up evaluation: same, better, worse) of infection, erythema (yes or no), presence of spontaneous discharge and tenderness (none, mild, or severe). In addition retrospective review of subjects’ Children’s Medical Center of Dallas medical record was performed 2 to 6 months after the initial visit to assess for complications and additional visits to our hospital. Children’s Medical Center of Dallas is the major pediatric hospital in Dallas, and it is the primary pediatric hospital in Dallas providing indigent and nonfunded care. Culture and susceptibility testing was done by the Children’s Medical Center, Dallas Microbiology Laboratory using standard automated microbiologic methods. No D tests were done.
For statistical analysis Fisher’s exact test was utilized (two tailed); P < 0.05 was considered significant.
We identified 69 children with skin and soft tissue abscesses with culture proven MRSA during the study period (Table 1). Figure 1 illustrates the management and outcome of the children. At initial presentation, tenderness at the site of infection was present in 97% (mild 40%, severe 57%) of the subjects, erythema in 92% and fever (≥101.0°F) in 48%. The Gram-stained smear of abscess fluid was positive for Gram-positive cocci in 91% of the patients.
The initial antibiotic therapy in the children managed as outpatients, before culture results were known, consisted of cephalexin in 52 (78%) patients, amoxicillin/clavulanate in 7 (10%), clindamycin in 5 (8%) and trimethoprim-sulfamethoxazole (TMP-SMX) combined with rifampin in 1. Two patients did not have their antibiotic prescription filled. In addition 20 (30%) of the patients received 1 dose of intravenous antibiotics (cefazolin, 14; ceftriaxone, 5; and ampicillin-sulbactam, 1) as part of their initial evaluation management.
All MRSA isolates were susceptible in vitro to rifampin, TMP-SMX, gentamicin and vancomycin, 88% to clindamycin and 13% to erythromycin. The antibiotics were changed to appropriate agents based on the results of susceptibility testing at the first follow-up in 21 (36%) of the patients managed as outpatients (Fig. 1). When a change was made, the antibiotics prescribed were TMP-SMX with rifampin in 18 (86%), TMP-SMX in 2 (10%) and clindamycin in 1 (4%). There were no statistically significant differences with regard to tenderness, erythema, wound discharge, fever or size between those subjects in whom the antibiotic therapy was changed to an effective agent and those in whom it was not.
Four patients (6%) initially treated with an ineffective antibiotic and managed as outpatients were admitted to the hospital on the first follow-up (Fig. 1). Reasons for admission included increase in size and erythema of the infected site in one patient and failure to improve as anticipated in the other three patients. No major infectious complications (e.g. sepsis, osteomyelitis or endocarditis) were reported during their hospitalization. A significant predictor of hospitalization on the first follow-up was having an infected area >5 cm in diameter at the initial evaluation (33% of patients with diameter >5 cm were later hospitalized vs. none with diameter ≤5 cm; P = 0.004). Ineffective initial antibiotic use from the initial evaluation was not a significant predictor of hospitalization (P = 1.0).
At the second follow-up, no patient required hospitalization. Of the patients who were initially treated with an ineffective antibiotic and managed as outpatients, mild tenderness was still present in three (6.3%), severe tenderness in none, erythema in seven (14%), fever (≥101.0°F) in none, wound discharge in 5 (10%) and size not improved in one (2%). At the second follow-up, there were no significant differences observed in tenderness, erythema, fever, wound discharge or size between those changed to an effective antibiotic and those not changed. There were six patients who did not have data available from the second follow-up visit.
In a retrospective hospital chart review 2 to 6 months after the initial visit, 3 (4.3%) patients had a recurrent MRSA skin infection. No major complications were found.
In this prospective observational study on the management and outcome of skin and soft tissue abscesses caused by CA-MRSA in previously healthy children, clinical improvement with incision and drainage was demonstrated in most instances despite treatment with antibiotics to which the organisms were not susceptible. The size of the infected area may be able to predict those CA-MRSA infections where incision and drainage along with appropriate antimicrobial therapy are important for a successful outcome; an infected site of >5 cm in diameter was more likely to fail management consisting of incision and drainage without effective antibiotic therapy.
Llera and Levy 4 conducted a randomized, double blind, placebo-controlled study in 50 adult patients who received antibiotic therapy or placebo after incision and drainage of skin and soft tissue abscess. They concluded that antibiotic therapy did not alter the outcome of the skin and soft tissue abscesses 1 week after incision and drainage, because 96% of subjects in each group improved. Although it is not a novel finding that therapeutic drainage, without adjuvant antibiotics, is generally effective for skin and soft tissue abscesses, we wished to assess this observation in the management of abscesses caused by CA-MRSA in children because some investigations have found worse outcomes with MRSA than methicillin-susceptible S. aureus infections. In addition the reports of invasive disease and death in children secondary to CA-MRSA infection have heightened concerns. 9 In a retrospective study, Fergie and Purcell 3 similarly reported that 29 children with CA-MRSA infection (mainly soft tissue infections, 11 of which required incision and drainage) recovered despite treatment with ineffective antimicrobial therapy.
CA-MRSA has become a common cause of skin and soft tissue abscess in children. The data presented in this study indicate that most CA-MRSA skin and soft tissue abscesses in otherwise healthy children can be managed with therapeutic drainage, without adjuvant antibiotics, if the infected site has a diameter of <5 cm. The applicability of these results to infants is not known.
Statistical consultation was obtained from Lonnie Roy of Children’s Medical Center of Dallas.
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