infection control and hospital epidemiology
june 2007, vol. 28, no. 6
concise communication
Evaluation of the Microbiology
of Soft-Tissue Abscesses in the Era
of Community-Associated Strains
of Methicillin-Resistant Staphylococcus
aureus: An Argument for Empirical
Contact Precautions
Thomas R. Talbot, MD, MPH; Joseph J. Nania, MD;
Patty W. Wright, MD; Ian Jones, MD;
Dominik Aronsky, MD, PhD
To ascertain the microbiology of skin abscesses, emergency department records were reviewed to identify patients with debrided skin
abscesses. Methicillin-resistant Staphylococcus aureus was isolated
from 255 (67.6%) of 377 culture samples from episodes in the adult
cohort and from 145 (79.7%) of 182 culture samples from episodes
in the pediatric cohort. Thus, empirical use of contact precautions
for patients with skin abscesses should be strongly considered.
Infect Control Hosp Epidemiol 2007; 28:730-732
Recently, the number of infections due to antibiotic-resistant
strains of Staphylococcus aureus has increased dramatically.1
In particular, the emergence of community-associated strains
of methicillin-resistant S. aureus (MRSA) has become a growing concern.2,3 To prevent transmission of MRSA, the Centers
for Disease Control and Prevention (CDC) recommends that
any patient with MRSA infection or colonization be placed
under contact precautions in medical settings.4 Such precautions have reduced the transmission of MRSA but can also
be costly to implement.5
According to CDC guidelines, the care of a patient with a
soft-tissue abscess involves only the use of standard precautions
for anticipated exposure to blood or body fluids during dressing
changes; use of other precautions for routine patient contact
is not recommended, except for those who are caring for a
patient with an uncovered or inadequately covered draining
lesion or with an abscess due to a multidrug-resistant organism,
such as MRSA, instances which require contact precautions.4
With the emergence of community-associated strains of MRSA,
it is unclear whether these isolation recommendations should
be altered. We hypothesized that MRSA is now the predominant cause of skin abscesses in adults and children. As such,
empirical use of contact precautions may be warranted for all
types of patient care activities performed for such persons to
prevent secondary MRSA transmission.
methods
We conducted a retrospective, descriptive epidemiologic study
to ascertain the microbiology of skin and soft-tissue abscesses
in patients who presented to an emergency department at a
tertiary care academic medical center. The study population
included all adult patients (ie, patients aged 18 years or older)
and pediatric patients (ie, those aged less than 18 years) who
met the following 3 criteria. (1) The patient visited the emergency department during the period from November 1, 2004,
through October 31, 2005. (2) The patient presented with 1
of 4 complaints coded in the International Classification of
Diseases, Ninth Edition (ICD-9): “infection of skin” (686.9),
“mass/superficial swelling” (782.2), “insect bite” (919.4), or
“sting: snake, lizard, spider” (989.5), as recorded in the computerized emergency department record. (3) The patient underwent an incision and drainage procedure, as determined
by institutional accounting data. Persons with a surgical site
infection, laceration infection, or abscess at a site other than
the skin (eg, odontogenic or perirectal abscess) were excluded from the study cohort. Investigators (T.R.T., J.J.N., and
P.W.W.) conducted chart reviews to confirm the presence and
location of the abscess (by provider diagnosis or description
of expressed purulent matter upon incision and drainage).
Microbiologic data collected included the time of culture
sample collection, time of final pathogen identification, and
culture results. The study was approved by the Vanderbilt
University institutional review board.
Comparisons were made between abscess episodes in which
specimens were obtained for culture (hereafter, cultured episodes) and episodes in which specimens were not obtained
(hereafter, noncultured episodes) using the Fisher exact test.
Data are reported per episode of infection. Analyses were
conducted using Stata software, version 7.0 (Stata).
results
Of 764 abscesses that were debrided, 63 were excluded due
to the presence of an alternate diagnosis. Among the 701
episodes included, 486 (69%) occurred in adult patients and
215 (31%) occurred in pediatric patients (Table). During the
study period, 43 (8.9%) of the adult patients and 8 (3.7%)
of the pediatric patients presented on multiple occasions with
skin abscesses that were debrided. In both the adult and pediatric cohorts, the most common anatomic sites for abscesses
were the extremities and the pelvis. Specimens for culture
were obtained for a majority of episodes (78% of adult episodes and 85% of pediatric episodes). Cultured episodes were
significantly more likely to occur in male patients (49% of
cultured episodes vs 38% of noncultured episodes; P p .02),
more often involved abscesses located on the pelvis (28% vs
18%; P ! .001), and less often involved abscesses located on
the upper extremities (25% vs 32%; P p .03). When cultured
and noncultured abscess episodes were compared, there were
no significant differences in patient age or the frequency of
other abscess sites.
soft-tissue abscesses, mrsa, and contact precautions
731
table. Characteristics of Episodes of Debrided Soft-Tissue Abscess in
Adult and Pediatric Emergency Department Patients
Variable
Patient age, mean (range), years
Male sex, % of patients
Location of abscessb
Head
Chest
Back
Upper extremity
Abdomen
Pelvis
Lower extremity
Not noted
Culture results
Abscess culture performed
S. aureus isolated (% of cultured
episodes)
MRSA isolated (% of cultured
episodes)
Time to pathogen identification,c
mean (95% CI), days
Adult
patient episodes
(n p 486)
Pediatric
patient episodes
(n p 215)
32.4 (18-77)
44.4
7.8 (0.2-18)a
51.6
49
12
21
137
35
122
145
0
(10.1)
(2.5)
(4.3)
(28.2)
(7.2)
(25.1)
(29.8)
18
7
4
43
19
62
60
2
(8.4)
(3.3)
(1.9)
(20.0)
(8.8)
(28.8)
(27.9)
(0.9)
377 (77.6)
182 (84.7)
298 (79.1)
169 (92.9)
255 (67.6)
145 (79.7)
2.4 (2.3-2.4)
2.2 (2.1-2.3)
note.
Data are no. (%) of episodes, unless otherwise indicated. Cultured episode,
episode of cutaneous abscess from which a culture sample was obtained; CI, confidence interval; MRSA, methicillin-resistant S. aureus.
a
Due to rounding, the value for the upper age range of the pediatric cohort (17.96)
and the lower age range of the adult cohort (18.04) both equal 18.
b
Counts sum to more than the total number of episodes because there were multiple
concurrent abscesses at different anatomic locations during some episodes.
c
Time from specimen collection to final pathogen identification and susceptibility
testing.
Among the adult cohort, MRSA was isolated in 255
(52.5%) of 486 abscess episodes and in 255 (67.6%) of 377
cultured episodes (Figure). Of the 25 soft-tissue abscess episodes in the adult cohort that required hospitalization, culture yielded MRSA in 14 (56%). Among the pediatric cohort,
MRSA was isolated in 145 (67.4%) of 215 abscess episodes
and in 145 (79.7%) of 182 cultured episodes. Of the 27 abscess
episodes in the pediatric cohort that required hospitalization,
culture yielded MRSA in 21 (78%). Episodes requiring hospitalization occurred significantly more often in males and
more often involved abscesses on the abdomen or upper extremities (data not shown). The mean time from culture sample collection to final identification of a causative pathogen
was 2.4 days (95% CI, 2.3-2.4) for episodes in the adult cohort
and 2.2 days (95% CI, 2.1-2.3) for episodes in the pediatric
cohort.
diatric nasal carriage of MRSA has increased 10-fold in Nashville in 4 years,6 and reports of severe MRSA infections in
previously healthy persons are increasing.2 Augmenting these
findings, the present study confirms that MRSA causes a sub-
discussion
In a remarkably short period of time, the incidence of infection and colonization with MRSA has markedly increased.1
MRSA now accounts for three-fourths of all pediatric community-onset S. aureus skin infections in some centers,3 pe-
figure. Culture findings for episodes of cutaneous abscess in
emergency department patients, by pathogen (abscess episodes in
adults, n p 377; abscess episodes in pediatric patients, n p 182).
MRSA, methicillin-resistant Staphylococcus aureus; MSSA, methicillin-sensitive S. aureus.
732
infection control and hospital epidemiology
june 2007, vol. 28, no. 6
stantial majority of debrided soft-tissue abscesses in both
adult and pediatric emergency department patients, which
mirrors other recently reported data on adults with softtissue infections presenting to university-affiliated emergency departments.7
In light of these findings, methods to prevent MRSA transmission in healthcare settings, such as the use of isolation
precautions, must be increasingly emphasized. Use of contact
precautions (in which care providers wear gowns and gloves
if direct contact with the patient or the patient’s environment
is anticipated, and private rooms or cohorting of patients is
used) is a cornerstone of efforts to reduce MRSA transmission4 and is recommended for all patients with either MRSA
infection or colonization. In contrast, in the absence of infection or colonization with an antibiotic-resistant pathogen,
current guidelines recommend use of contact precautions for
patients with a skin or soft-tissue abscess only if the lesion
is not covered by a dressing or the dressing does not contain
drainage adequately.4 The finding that MRSA causes the majority of these infections, however, argues for the use of empirical contact precautions for all patients with a skin or softtissue abscess because of concerns about colonization with
multidrug-resistant bacteria and the risk of secondary transmission of MRSA by healthcare workers.
Although most patients with a skin or soft-tissue abscess
in our study did not require hospitalization, transmission of
MRSA from infected (and presumptively colonized) individuals to other patients via healthcare workers may have occurred, even during the limited time spent in the emergency
department before discharge. Empirical use of contact precautions for patients presenting with a soft-tissue abscess who
require hospitalization may have an even greater impact, as
use of empirical precautions would have averted more than
2 days of unprotected exposure, compared with precautions
implemented after identification of MRSA.
In 2003, the Society for Healthcare Epidemiology of America (SHEA) recommended a comprehensive strategy to prevent MRSA transmission in healthcare settings, including
screening and empirical isolation of persons at high risk for
MRSA carriage.8 The findings of the current study may also
impact isolation practices in healthcare institutions that have
fully implemented the SHEA recommendations. Specifically,
the classification of high-risk patients is determined institutionally, on the basis of patient populations and pathogen
prevalence,5 and may include prior healthcare exposures, antimicrobial use, and severity of comorbid illnesses. However,
as community-associated MRSA soft-tissue infections often
occur in previously healthy persons without prior healthcare
exposure, such individuals may not be deemed high-risk by
healthcare providers.
In summary, MRSA was responsible for over two-thirds of
all adult episodes of debrided skin and soft-tissue infections
and for three-fourths of all pediatric episodes. These findings
argue that implementation of empirical contact precautions
for all patients with soft-tissue abscesses should be considered.
acknowledgments
We acknowledge Jennifer Pritchett for the linkage to the institutional financial
data and C. Buddy Creech MD, MPH, and William Schaffner, MD, for their
critical review of the manuscript.
Financial support. T.R.T. has received research funding from Nabi Pharmaceuticals and support from GlaxoSmithKline.
Potential conflicts of interest. All authors report no conflicts of interest
relevant to this article.
From the Division of Infectious Diseases in the Department of Medicine
(T.R.T., P.W.W.), the Division of Infectious Diseases in the Department of
Pediatrics (J.J.N.), and the Departments of Preventive Medicine (T.R.T.),
Emergency Medicine (I.J., D.A.), and Biomedical Informatics (D.A.), Vanderbilt University School of Medicine, Nashville, Tennessee.
Address reprint requests to Thomas R. Talbot, MD MPH, A-2200 Medical
Center North, 1161 21st Avenue South, Vanderbilt University Medical Center,
Nashville, TN 37232 (tom.talbot@vanderbilt.edu).
Presented in part: 16th Annual Scientific Meeting of the Society of Healthcare Epidemiology of America; Chicago, IL; March 19, 2006 (Abstract 50).
Received June 20, 2006; accepted September 5, 2006; electronically published April 19, 2007.
䉷 2007 by The Society for Healthcare Epidemiology of America. All rights
reserved. 0899-823X/2007/2806-0017$15.00. DOI: 10.1086/516799
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