American Journal of Emergency Medicine (2012) 30, 302-310

Original Contribution

Practice patterns and management strategies for purulent skin and soft-tissue infections in an Urban academic ED

Larissa May MD, MSPH ^a,?, Katherine Harter BS ^b, Kabir Yadav MDCM, MS ^a, Ryan Strauss MPH, PA ^a, Jameel Abualenain MD ^a, Amy Keim PA ^a, Gillian Schmitz MD ^c

^aDepartment of Emergency Medicine, The George Washington University, Washington, DC, USA

^bThe George Washington School of Medicine, Washington, DC, USA

^cDepartment of Emergency Medicine, Washington Hospital Center, Washington, DC, USA

Received 16 September 2010; revised 22 November 2010; accepted 30 November 2010

Abstract

Background: Community-acquired methicillin-resistant Staphylococcus aureus (MRSA) is the most common cause of purulent skin and soft-tissue infections (SSTIs) in the Unites States. Little is known regarding health care provider management strategies for abscesses in the emergency department (ED). Understanding variability in practice patterns could be an important step in implementing evidence- based guidelines.

Objectives: The objectives of this study are to describe practice patterns for purulent SSTI in a single, urban, academic ED, including Antibiotic selection and incision and drainage (I & D) technique, and to compare these practices with current evidence.

Methods: Prospective data were collected on a convenience sample of adults presenting to our urban, academic ED (annual volume, 65 000 per year) between June 2009 and May 2010. Characteristics of patients and their providers were collected as well as specific management strategies including use of irrigation, packing, and antibiotics.

Results: One hundred forty-five patients were enrolled. Most SSTIs were single (80.4% abscesses), most commonly on the extremities (29.8%). Both I & D and antibiotics were used 79.9% of the time, with the largest predictor for the addition of antibiotics being erythema more than 2 cm (odds ratio, 4.52; 95% confidence interval, 1.39-14.7); I & D technique varied by provider-type and experience. Providers suspected MRSA in 75% of cases, despite only 48% demonstrating MRSA on culture. Many patients received antimicrobials after I & D, even in those with 2 cm or less abscesses (57.5%).

Conclusions: Practice patterns vary significantly, especially antibiotic overuse, at least in this urban academic ED. Further study should be undertaken to evaluate factors that influence management strategies for SSTI.

(C) 2012

Background

* Corresponding author. Tel.: +1 202 741 2920; fax: +1 202 741

2921.

E-mail address: [email protected] (L. May).

For the last decade, the Incidence of infections from community-acquired methicillin-resistant Staphylococcus aureus (MRSA) (CA-MRSA) has dramatically increased, and CA-MRSA is now considered as the most common

0735-6757/$ – see front matter (C) 2012 doi:10.1016/j.ajem.2010.11.033

identifiable cause of skin and soft-tissue infections (SSTIs) in the United States [1,2]. Emergency departments (EDs) are the primary treatment site for SSTIs [3-5]. Greater than 80% of ED patients with CA-MRSA SSTI are treated as outpatients, and thus the overall health burden of MRSA- related SSTI is significant [1,6].

Although consensus documents exist regarding treatment of SSTI’s in the ED, recommendations are vague because of lack of quality prospective data on provider practice patterns [7,8]. Infectious Disease Society of America guidelines recommend incision and drainage (I & D) of the pus, including breaking up of the loculations in the cavity and covering the site with a dry dressing. Packing is used by some providers; however, it is not universally recommended [9]. Evidence from retrospective studies and 2 recent randomized controlled trials suggests that antibiotic use may not be necessary after I & D in uncomplicated abscesses [10,11]. Despite consensus recommendations, it is unclear which treatment factors, including antimicrobial therapy, improve patient outcomes. There are also potential public health and clinical ramifications of antibiotic overuse and lack of adequate transmission-related precautions for patients with purulent SSTIs. Although provider variation exists in the management of purulent SSTI, the extent and signifi- cance of this variation are unclear. Understanding the factors associated with provider management of abscesses and the resultant effects on outcomes could be an important step in implementing Evidence-based guidelines for the ED man- agement of purulent SSTI.

Objectives

The principal objective of this study is to describe factors associated with antibiotic use in conjunction with I & D in the management of purulent SSTI in an urban academic ED. A second objective is to examine Provider factors, including provider-type and experience (defined as no. of previous I & Ds) with the use of irrigation, packing, and incision length.

Methods

Study design

This is a prospective study of a convenience sample of adult patients presenting with purulent SSTI. All eligible partici- pants were identified before I & D during the hours when research assistants were available for consent and enrollment procedures, generally from 8 AM to midnight, 5 days per week.

Setting

This study is conducted at a single, urban, academic ED with an annual volume of approximately 65 000 cases per year. During the study period, our ED saw 803 patients with purulent SSTI.

Most patients with purulent SSTI are seen in the fast track by certified physician assistants under the supervision of board-eligible or board-certified emergency physicians, although emergency medicine (EM) residents, non-EM residents, and students may also treat patients with purulent SSTI. Students and residents are supervised by the attending physician and/or the PA.

Selection of participants

All adult patients 18 years and older presenting to the ED with a clinically diagnosed purulent SSTI (tender, swollen, fluctuant, or superficial skin lesion) were eligible for enrollment in the study. Postoperative or postprocedure Wound infections were excluded. Additional exclusion criteria included the inability to speak or read English and a lack of ability to provide informed consent.

Data sources

Methods of measurement

Data were collected on all enrolled participants and their providers. At initial enrollment, a member of the research team collected data on patients and their providers using a standardized data collection sheet. The form was developed by members of the research team based on a literature review of patient risk factors and treatment options for SSTI. The data collection sheet consisted of 27 questions in total. A closed- ended question format was used, which allowed a larger number of variables to be assessed by the participants [12]. We collected information on patient characteristics including demographic factors (age, sex, and medical history) and SSTI characteristics (size, location, and erythema). Abscess size was determined by provider estimation into specific categories for the largest diameter of fluctuance and induration. Abscess erythema was classified by clinician-estimated diameter of erythema, categorized by size. Abscess depth was determined by probing of the abscess cavity. We also collected data on Provider characteristics, including provider- type (attending physician, resident, PA, student) and I & D experience (no. of previous I & D procedures performed). Management strategies were also recorded, including I & D technique (sterile gloves/gown, contact precautions, incision length, irrigation, packing technique, and debridement) and use and selection of antimicrobial therapy. A wound culture was performed on patients undergoing I & D to determine microbial pathogen and susceptibility results.

Variables

The main outcome variable of interest was the use of systemic antibiotics in addition to I & D compared to I & D alone. The main predictor variables for this outcome were provider-type, abscess size, erythema size, abscess location, and patient characteristics including age, race, presence of comorbidities, and history of MRSA or purulent SSTI. Other

outcomes of interest were aspects of the I & D technique: packing use, irrigation, and incision size. The main predictor variables for these outcomes were provider-type and experi- ence, defined as numbers of previously performed I & D.

Statistical analysis methods

Descriptive statistics were conducted for patient and purulent SSTI characteristics and management strategies. To identify the association between predictor variables and management strategies, unadjusted odds ratios (ORs) and adjusted ORs (aORs) and 95% confidence intervals (CIs) were calculated using logistic regression. All statistical analyses, including descriptive frequencies and bivariate statistics, were performed using SAS 9.2 (SAS Institute, Cary, NC).

Human subjects protection issues

This study was approved by our university institutional review board. Informed consent was obtained from all patient study participants. A waiver of documentation of consent was obtained for the providers who participated in the study.

Results

Patient characteristics

A total of 145 patients were enrolled in a 12-month period from June 2009 to May 2010, representing approximately

Table 1 Patient characteristics (N = 145)

Demographic characteristics of enrolled participants n (%)

Sex Male 65 (44.8) Female 80 (55.2) Race Black/African-American 112 (77.2) White 21 (14.5) Other 7 (4.8) Mean age (SD) 38 (13.2) Median age 37 Range of age (y) 18-82 Interquartile range (y) 27-47 Patient-reported comorbidities a 37 (29.8) Diabetes mellitus 19 (15.3) HIV 11 (8.9) None 87 (70.2) Patient-reported hospitalization in past 12 mo 24 (17.4) Patient-reported history of abscess or MRSA 82 (58.6) Patient-reported contact with MRSA 29 (21.0) Patient awareness of MRSA 55 (39.6) Patient on antibiotics at time of enrollment 22 (16.5)

a Comorbidities include diabetes mellitus, HIV, intravenous drug abuse, Hepatitis C, sarcoidosis, end-stage renal disease.

Clinical characteristics of abcesses n (%)

Abscess type Cutaneous 126 (92.7) Other (paronychia, pilonidal) 10 (7.3) Single vs multiple abscesses Single 115 (80.4) Multiple 28 (19.6) Abscess location Axilla 19 (13.5) Buttock/perineum 36 (25.5) Extremities 42 (29.8) Face 14 (9.9) Trunk 30 (21.3) Abscess diameter <=2 cm 79 (56.9) N2 cm 60 (43.1) Abscess depth <=2 cm 112 (83.6) N2 cm 22 (16.4) Erythema size <=2 cm 63 (47.0) N2 cm 71 (53.0) Provider suspicion of MRSA 101 (74.8) Culture results MRSA 56 (47.5) MSSA 17 (14.4) Other a 45 (38.1)

a Other includes Proteus mirabilis, Enterococcus, Stenotrophas maltophilia, ? Streptococcus, coagulase-negative Staphylococcus, anaerobic gram negative rods, gram positive cocci (GNR/GPC), group B Streptococcus, Streptococcus pneumoniae, Pseudomonas, and other.

18% of all patients seen for initial and repeat visits for purulent SSTI. Patient demographics and characteristics are listed in Table 1.

Table 2 Purulent SSTI characteristics (N = 145)

Purulent SSTI characteristics

Most purulent SSTIs studied were single (80.4%), Cutaneous abscesses (92.7%), and were most commonly located on the extremities (29.8%) or buttock/perineum regions (25.5%), as shown in Table 2. Seven percent of abscesses were pilonidal or paronychias. In general, most purulent SSTIs were small, with a diameter less than 2 cm (56.9%), a depth less than 2 cm (83.6%), and an erythema diameter of less than 2 cm (47.0%). Although providers suspected MRSA 74.8% of the time, only 47.5% of cultures grew MRSA (Table 2). Ninety-five percent of isolates were sensitive to clindamycin and 97%, to trimethoprim-sulfamethoxazole (TMP-SMX). Our clinical laboratory routinely performs d-testing for S aureus isolates that are erythromycin resistant but clindamycin susceptible. In our study, there was a 2% rate of inducible clindamycin resistance.

Treatment characteristics

Most providers who treated the study SSTIs were PAs (63.9%). Most had performed at least 50 I & Ds previously (50.7%). Incision and drainage procedures were performed on 93.8% of enrolled patients with purulent SSTI, with specific techniques described in Table 3. Antimicrobials were prescribed to 84.1% of all enrolled patients. Providers reported use of sterile gloves 49.6% of the time and contact precautions in 54.2% (Table 3).

Use of antimicrobials for patients undergoing I & D

Erythema size greater than 2 cm was significantly associated with the use of antibiotics in addition to both I & D and antibiotics (OR, 4.52; 95% CI, 1.39-14.75). This

n (%)

Provider characteristics provider type Attending physician 4 (3.0) Resident 19 (14.3) PA 85 (63.9) Student (MD or PA student) 25 (18.8) Provider experience <=50 prior I & Ds performed 65 (49.3) N50 prior I & Ds performed 67 (50.7) Management strategies I & D performed 135 (93.8) Antibiotics prescribed 122 (84.1) I & D performed plus antibiotics prescribed 115 (79.9) I & D plus TMP-SMX 36 (29.5) I & D plus TMP-SMX and keflex 25 (20.5) I & D plus clindamycin 38 (31.2) I & D plus other 16 (13.1) Disposition Routine discharge 134 (94.4) Hospital admission 8 (5.6) Contact precautions used 71 (54.2) Patient instructed on contact precautions 5 (3.9) I & D technique characteristics (n = 135) Irrigation used 14 (10.8) Incision size <=1 cm 94 (71.8) N1 cm 37 (28.2) Packing Tight 25 (18.9) Loose 81 (61.4) None 26 (19.7) Debridement done 7 (5.3) Sterile precautions used (sterile gloves) 66 (49.6)

relationship remained significant after adjusting for age, race, and comorbidities (aOR, 4.55; 95% CI, 1.11-18.66). There was no difference observed in decision to use both I & D plus antibiotics among the PAs as compared to physicians (residents or attending physicians) (OR, 1.01; 95% CI, 0.26-3.97). For details, refer to Table 4.

Incision and drainage techniques

Physician assistants were less likely than physicians to use irrigation (OR, 0.11; 95% CI, 0.03-0.41), and this relationship was statistically significant. When adjusting for provider-type and experience, the relationship remained significant (aOR, 0.17; 95% CI, 0.04-0.76). Provider experience (N50 I & Ds performed) was also associated with increased irrigation use; however, the aOR was not significant (Table 5).

Discussion

Table 3 Provider characteristics, management characteristics, and I & D technique (N = 145)

We found that nearly all of our patients received antimicrobial therapy despite current recommendations and evidence. Consensus guidelines for the management of purulent SSTI have been developed by the Centers for Disease Control and Prevention [7] and by the Infectious Disease Society of America [9]. These guidelines recom- mend I & D as the primary therapy for cutaneous abscesses. Nearly all patients were treated as outpatients (94%), suggesting that most were uncomplicated purulent SSTI. Incision and drainage technique displayed variation by provider-type and experience, suggesting a wide variation in standard practice even at a single institution.

Use of antimicrobials

Practice patterns vary significantly from existing guide- lines, at least in this urban academic ED. A large proportion of patients are receiving antimicrobials after I & D, even in those with small purulent SSTI (57.5%). The literature does not support routine use of antibiotic therapy with I & D for uncomplicated cutaneous purulent SSTI in healthy adult patients [13,14]. For a typical, uncomplicated cutaneous abscess, I & D alone should provide sufficient therapy for clinical improvement, given that patients treated with nonsusceptible antibiotics tend to improve regardless, even in cases of CA-MRSA [1]. Systemic antibiotics are generally reserved for extensive surrounding cellulitis, systemic symptoms, or patient comorbidities; however, this evidence is based on opinions from expert panels rather than Prospective trials (level 3 evidence) [9]. Patients with preexisting conditions, particularly diabetes and HIV, may be at greater risk for unusual pathogens and may require antibiotics in addition to I & D [13].

Provider characteristics
Provider type
Physician	20	(17.5)	3	(15.8)	1.00	v1.00
PA	74	(64.9)	11	(57.9)	1.01 (0.26-3.97)	1.20 (0.28-5.14)
Student	20	(17.5)	5	(26.3)	0.60 (0.13-2.86)	0.76 (0.13-4.29)
Abscess characteristics
Abscess size
<=2 cm	65	(57.5)	8	(44.4)	1.00	1.00
N2 cm	48	(42.5)	10	(55.6)	0.59 (0.22-1.61)	0.44 (0.14-1.43)
Erythema size
<=2 cm	46	(41.8)	13	(76.5)	1.00	1.00
N2 cm	64	(58.2)	4	(23.5)	4.52 (1.39-14.75) ?	4.55 (1.11-18.66) ?
Abscess location
Face	10	(8.9)	1	(5.0)	1.00	1.00
Extremities + axilla	55	(48.7)	2	(10.0)	2.75 (0.23-33.27)	2.76 (0.21-37.01)
Trunk + buttock/perineum	48	(42.5)	17	(85.0)	0.28 (0.03-2.37)	0.31 (0.03-2.99)
Patient characteristics
Age (y)
<=40	65	(56.5)	12	(60.0)	1.00
N40	50	(43.5)	8	(40.0)	1.15 (0.44-3.04)	–
Race
White/other	23	(20.7)	3	(15.8)	1.00
Black/African American	88	(79.3)	16	(84.2)	0.72 (0.19-2.68)	–
Comorbidities
None	67	(69.1)	15	(88.2)	1.00
Any	30	(30.9)	2	(11.8)	3.36 (0.72-15.61)	–
Diabetes	16	(16.5)	1	(5.9)	3.16 (0.39-25.53)	–
HIV	9	(9.3)	1	(5.9)	1.64 (0.19-13.82)	–
Note: where values do not add up to n = 115 or n = 20, respectively, there were missing data. a Analysis was conducted using logistic regression. b Adjusted for age (<=40 vs N40), race (black/African American vs white/other) and the presence of any comorbidities; analysis conducted using logistic regression. * P b .05.

Of our enrolled patients, 70.2% had no comorbidities. A possible factor driving clinician decisions on antibiotic use may be the high rate of previous hospitalization (17%), increasing the concern for the presence of MRSA and resistance or virulence in potential hospital-acquirED strains; although, antibiotics active against hospital-acquired (HA)- MRSA, such as vancomycin or linezolid, were not selected. Sixteen percent of patients were on antibiotics without I & D before enrollment, which may have influenced antibiotic selection toward MRSA active agents. When antimicrobials were used, clindamycin was used most often (31.2%) followed by TMP-SMX (29.5%), supporting recommenda- tions made in the literature that in areas of high-MRSA prevalence, non-? lactams can be used (TMP-SMX, clindamycin, or tetracyclines) [13,15].

Table 4 Unadjusted and adjusted characteristics associated with the use of I & D procedure plus antimicrobials (n = 135)

I & D plus antimicrobial, n = 115

n (%)

I & D used alone

(no antibiotics), n = 20

n (%)

Unadjusted ^a OR aOR ^b for I & D + for I & D + Antibiotics Antibiotics aOR OR (95% CI) (95% CI)

Several studies have examined the efficacy of I & D procedures done with and without antibiotics on clinical

outcomes. Past studies have shown no difference in resolution of purulent SSTI after I & D alone compared to I & D plus antibiotic use [16,17]; recent studies done in areas with high-MRSA prevalence have shown similar findings [18]. Additional studies on healthy patients found no difference in Treatment outcomes in patients with treated with susceptible antibiotics and nonsusceptible antibiotics [1,10,11,18]. Furthermore, there is retrospective data sug- gesting that use of a susceptible antibiotic may be associated with improved odds of clinical resolution after controlling for I & D [19-22] and oral antimicrobials are unproven for large abscesses [22].

Of note, 58.6% of enrolled patients self-reported a history of MRSA or abscess within the last 12 months. More recent literature suggests that antibiotics used in conjunction with I & D may decrease the recurrence of abscesses [11,14,18].

Physician c	15 (14.2)	8 (30.8)	1.00	1.00
PA	69 (65.1)	15 (57.7)	2.45 (0.88-6.83)	2.13 (0.65-7.01)
Student d	22 (20.8)	3 (11.5)	3.91 (0.89-17.19)	4.03 (0.91-17.82)
Provider experience <=50 prior I & Ds	50 (47.6)	14 (53.9)	1.00	1.00
N50 prior I & Ds	55 (52.4)	12 (46.1)	1.28 (0.54-3.04)	1.25 (0.42-3.69)
	Irrigation used, n = 14	No Irrigation used, n = 116	Unadjusted a OR	aOR b for irrigation

Physician c	7 (50.0)	15 (12.9)	1.00	1.00
PA	4 (28.6)	80 (69.0)	0.11 (0.03-0.41) ?	0.17 (0.04-0.76) ?
Student d	3 (21.4)	21 (18.1)	0.31 (0.07-1.38)	0.28 (0.06-1.26)
Provider experience <=50 prior I & Ds	11 (78.6)	52 (45.2)	1.00	1.00
N50 prior I & Ds	3 (21.4)	63 (54.8)	0.23 (0.06-0.85) ?	0.42 (0.09-2.09)
	Large incision (N1 cm) n = 37	Small incision (<=1 cm) n = 94	Unadjusted a OR	aOR b for large
	n (%)	n (%)	for large incision (N1 cm) OR (95% CI)	incision (N1 cm) aOR (95% CI)
Provider type Physician c	7 (18.9)	16 (17.0)	1.00	1.00
PA	22 (59.5)	62 (66.0)	0.81 (0.30-2.23)	0.57 (0.17-1.87)
Student d	8 (21.6)	16 (17.0)	1.14 (0.34-3.90)	1.23 (0.36-4.27)
Provider experience <=50 prior I & Ds	17 (47.2)	47 (50.0)	1.00	1.00
N50 prior I & Ds	19 (52.8)	47 (50.0)	1.12 (0.52-2.41)	1.70 (0.61-4.76)
a Analysis was conducted using logistic regression. b Adjusted for provider-type and provider experience. c Physician includes attending physician or resident physicians. d Student includes medical and PA students. * P b .05.

There was an increased use of antibiotics for associated erythema more than 2 cm, suggesting that the use of antimicrobials was for presumed cellulitis. Community- acquired methicillin-resistant S aureus is typically associated with large abscesses with intense erythema [23], and thus erythema alone may not predict need for antibiotics. In a large, prospective, multicenter trial, no significant differ- ences were found between resolutions in patients who received discordant antibiotics for the organism [1], confirming earlier similar findings [24]. Despite this, many are still treating abscesses with antibiotics [25].

Table 5 Unadjusted and adjusted characteristics associated with I & D technique (n = 135)

Packing used, n = 106 No Packing used, n = 26

n (%) n (%)

Unadjusted ^a OR for packing use OR (95% CI)

aOR ^b for packing use aOR (95% CI)

Provider type

n (%)

n (%)

for irrigation use OR (95% CI)

use aOR (95% CI)

Provider type

It is unclear what factors motivate the use of antimicro- bials after adequate I & D for small purulent SSTI in healthy patients. Given that nearly 3/4 of cases in this study were suspected to be MRSA, provider selection of antibiotics may suggest concerns about bacterial virulence in this population. In a previously published study, 53% of North American

health care providers surveyed including physicians, medical students, and other health care professionals stated they would treat a presumably healthy athlete with an abscess with an anti-MRSA antibiotic after I & D [26]; this study did not examine survey results by provider-type. Another study surveyed attending physicians and board-certified fellows in pediatrics and emergency medicine on management strate- gies they would use for a series of clinical vignettes of children with SSTIs; they showed great variation in their motivations and selection of management strategies for pediatric SSTI. Most (94%) indicated they would use an antimicrobial after I & D, and more than 50% indicated that they would select TMP-SMX (TMP-SMX, bactrim) fol- lowed by clindamycin (32%) [27]. Thus, despite published evidence, antimicrobial use for uncomplicated SSTI remains pervasive, and use trends in this study as well as prior studies suggest provider concerns regarding CA-MRSA.

Incision and drainage technique

There is no standard I & D technique [14,28], but current recommendations are to break up loculations and debride necrotic tissue [8] and to use universal precautions [29]. No studies, to our knowledge, have been done on the use of sterile vs nonsterile gloves in I & D; however, it is reasonable to use sterile procedures whenever possible [29]. Half of our providers chose to use sterile precautions. Although previous investigations have evaluated the association of outcome with management techniques, little consensus has been reached, and limited evidence-based guidelines exist for patients with MRSA-related abscesses in the ED [1,30,31]. Before this study, no studies, to our knowledge, have evaluated Management strategy by provider-type. Most published surveys have been of physicians; however, in many ED and urgent care settings, wound care is provided by midlevel providers. [5,6].

In our study, I & D technique varied in the use of sterile precautions, size of incision, and use of packing and also varied by provider-type. Certain sources recommend longer incisions to prevent the wound from closing before the abscess has finished draining, which can contribute to recurrence [13]. In our study, there was a trend for increased incision size for physicians compared to PAs and with provider experience.

Irrigation is also recommended in the literature; however, it has not been experimentally proven to significantly change the outcome of the abscess healing [13]. In our ED, PAs tend both to have the most procedural experience (compared to residents) and perform most of the wound care. Our data showed that PAs were less likely to use irrigation as compared with attending physicians and residents. Providers with more procedural experience were also less likely to use irrigation as compared to those with less experience; however, because our PAs, in many cases, have more experience than student or resident providers, this may reflect PA technique.

The use of packing is recommended to allow continued drainage after I & D [13,29]; however, these recommenda- tions lack evidence, and consensus guidelines leave packing up to the discretion of the provider [9]. Very few data are published on the use of packing in the treatment of cutaneous abscesses; however, a recent pilot study showed that packing may cause increased pain and is not associated with improved outcome [32]. Our data showed a trend for PAs and students being more likely to use packing as compared to physicians; however, this was not statistically significant. Student provider-types performed I & D procedures under the supervision and instruction of physicians or PAs in the ED. The provider overseeing their work influenced their choices for incision, irrigation, and packing.

Another point of interest is the Centers for Disease Control and Prevention recommendation for the use of contact precautions for all patients with purulent infections being admitted to the hospital to prevent hospital-based transmis-

sion of MRSA [33]. In our study, providers only used contact precautions 54.2% of the time. Although nearly all patients were treated as outpatients, the ED is the entry point to the hospital, and MRSA infection rates in the community have been found to be associated with Infection rates in the hospital [34-36]. To decrease community-based transmission of MRSA, it is prudent to education patients on contact precautions and transmission risks for possible MRSA; however, this may not be practical given that approximately half of patients do not even have MRSA, and culture results are not available for several days after ED visit even when they are sent. We found that only a small number of patients (3.9%) were documented to have been educated on contact precautions during their stay in ED; although, we are limited by the fact that documentation of contact precautions alone is only a surrogate for actual compliance. Past studies have shown that Infection control is difficult to establish in an ED setting and can overwhelm scarce resources [8].

Strengths and limitations

There were several limitations of this study. First, it was a single-center study on a convenience sample with a small sample size. We hope to direct future research to a multicenter setting to examine these factors in non-emergency medicine providers from different specialties and different regions of practice to observe variation in management technique. Another limitation was that most patient data were self- reported, which could have introduced recall or reporting biases to our data. The investigators chose to use estimated abscess and erythema size rather than actual measurements because providers do not typically measure the diameter of erythema or abscess size when making estimates for treatment purposes. Thus, abscess size, erythema, and incision size were estimated by clinicians and were not actually measured, and interrater reliability was not done. The use of ultrasound for the determination of size was at the discretion of the physician; thus, it is possible that some measurements are based on actual measurements. Although we tried to assess the variables associated with antibiotic use in patients with purulent SSTI, we did not directly ask providers for the reason why they choose antibiotics. A strength of this study is that data were prospectively collected on actual practice patterns and were not survey-based. Another strength is that it is one of the first studies to compare provider-types with regard to management strate- gies of SSTI. Where most prior studies have examined physician opinions on SSTI management, we found that because most providers were not physicians, it was important to consider differences in provider-type on practice patterns.

Conclusions and recommendations

The purpose of this study is to describe practice patterns for purulent SSTI in an urban academic ED including

management characteristics, choice of antimicrobial therapy, and I & D technique and to determine if any variables predicted antibiotic use. We found that erythema size greater than 2 cm predicted antimicrobial use, possibly reflecting concerns regarding cellulitis. Our second objective is to determine if provider-type and experience predicted I & D management. Our findings demonstrated that there is a wide range of management strategies in this urban ED, with a higher than expected rate of antibiotic use. Physician assistants and those who had greater procedural experience were less likely to use irrigation. Further investigation should be done to evaluate factors contributing to varying management strategies of providers and to provide confi- dence in the use of evidence-based practice. Given provider concerns regarding MRSA, further study should be under- taken to identify patients with non-MRSA abscesses in near real-time. If antibiotic overreliance is due to concern for organism virulence, the availability of rapid diagnostic testing for MRSA could promote Antimicrobial stewardship in the ED. Additional work should be done to evaluate I & D technique on prospective outcomes to better determine the most effective strategies for purulent SSTI healing and decreased recurrence of abscesses.

Acknowledgment

The authors thank all members of the research team for consenting and enrolling patients and data collection, with special thanks to Virginia Lathrop, Dallen Herzog, Norah Algarzae and Loveleen Singh. The authors would also like to acknowledge Drs Angelo Elmi and Heather Young for their advice on the statistical analysis and Dr Manya Magnus for her consultation on epidemiologic analysis.

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