Infectious disease/original research
Increased US Emergency Department Visits for Skin and Soft Tissue Infections, and Changes in Antibiotic Choices, During the Emergence of Community-Associated Methicillin-Resistant Staphylococcus aureus

https://doi.org/10.1016/j.annemergmed.2007.12.004Get rights and content

Study objective

Test the hypotheses that emergency department (ED) visits for skin and soft tissue infections became more frequent during the emergence of community-associated methicillin-resistant Staphylococcus aureus (MRSA), and that antibiotics typically active against community-associated MRSA were chosen increasingly.

Methods

From merged National Hospital Ambulatory Medical Care Survey data for 1993–2005, we identified ED visits with diagnosis of cellulitis, abscess, felon, impetigo, hidradenitis, folliculitis, infective mastitis, nonpurulent mastitis, breast abscess, or carbuncle and furuncle. Main outcomes were change over time in rate of ED visits with such a diagnosis and proportion of antibiotic regimens including an agent typically active against community-associated MRSA. We report national estimates derived from sample weights. We tested trends with least squares linear regression.

Results

In 1993, infections of interest were diagnosed at 1.2 million visits (95% confidence interval [CI] 0.96 to 1.5 million) versus 3.4 million in 2005 (95% CI 2.8 to 4.1 million; P for trend <.001). As a proportion of all ED visits, such infections were diagnosed at 1.35% in 1993 (95% CI 1.07% to 1.64%) versus 2.98% in 2005 (95% CI 2.40% to 3.56%; P for trend <.001). When antibiotics were prescribed at such visits, an antibiotic typically active against community-associated MRSA was chosen rarely from 1993 to 2001 but increasingly thereafter, reaching 38% in 2005 (95% CI 30% to 45%; P for trend <.001). In 2005, trimethoprim-sulfamethoxazole was used in 51% of regimens active against community-associated MRSA.

Conclusion

US ED visits for skin and soft tissue infections increased markedly from 1993 to 2005, contemporaneously with the emergence of community-associated MRSA. ED clinicians prescribed more antibiotics typically active against community-associated MRSA, especially trimethoprim-sulfamethoxazole. Possible confounders are discussed, such as increasing diabetes or shifts in locus of care.

Introduction

Staphylococcus aureus is a major cause of both abscesses and nonpurulent skin and soft tissue infections.1, 2 Strains resistant to β-lactams, known as methicillin-resistant S aureus (MRSA), emerged in the 1960s. These were found predominantly in patients exposed to health care facilities. This changed when new “community-associated” strains emerged in the mid-1990s, and community-associated MRSA is now the leading identifiable cause of skin and soft tissue infections in US emergency department (ED) patients (though generally the cause is identifiable only when the infection is purulent).1, 2

Recent studies have shown that cultures of ED patients’ abscesses are likely to yield community-associated MRSA.1 However, we still do not know whether abscesses and other infections commonly caused by S aureus are more common since the emergence of community-associated MRSA. Have ED visits for skin and soft tissue infections increased since community-associated MRSA was discovered? Or has this organism merely replaced others, with the underlying disease incidence remaining the same? Given the heterogenous patterns of antibiotic resistance exhibited by this organism, it is also important to monitor physician prescribing practices. Have prescribing practices changed in parallel to changes in disease incidence and cause?

We seek to determine whether the annual rate of ED visits for skin and soft tissue infections often caused by S aureus has changed since community-associated MRSA was first described in the mid-1990s. We hypothesized that from 1993 to 2005, there was a nationwide increase in ED visits attributable to such infections. We also hypothesized that US ED clinicians increased their use of antibiotics typically active against community-associated MRSA when prescribing antibiotics for such infections. To test these hypotheses, we sought data on ED utilization for relevant infections and prescribing practices for not only today but also the period before community-associated MRSA was described. Because it is not possible to initiate prospective surveillance after the fact (ie, after the new organism was described), we required a preexisting surveillance data set. Only 1 such data set exists for the US ED setting: the National Hospital Ambulatory Medical Care Survey (NHAMCS).3

Section snippets

Study Design and Setting

We conducted a secondary analysis of NHAMCS data for 1993 to 2005. NHAMCS is a probability sample of ED visits in all 50 states and the District of Columbia, representing all US EDs, excluding federal, military, and Veterans Administration hospitals.3 Trained staff collect data using standardized forms during randomly assigned 4-week periods. All collected forms are sent to the Constella Group (Durham, NC) and coded by using the International Classification of Diseases, Ninth Revision, Clinical

Results

From 1993 through 2005, the NHAMCS sampled 374,891 ED visits. Each year, 352 to 418 EDs participated.10 An infection of interest was diagnosed at 6,628 of these visits. This allows us to estimate that there were 1.3 billion total ED visits in the United States during this period (95% CI 1.2 to 1.4 billion), with diagnosis of an infection of interest at 23 million (95% CI 21 to 25 million), or 1.7% of all ED visits (95% CI 1.6% to 1.8%). Patient age was younger than 18 years for 18% (95% CI 17%

Limitations

An important unanswered question is whether community-associated MRSA plays a role in nonpurulent skin and soft tissue infections (eg, cellulitis), as well as purulent ones (abscess, folliculitis, etc). A flaw in the ICD-9-CM diagnostic categorization system is that cellulitis and abscess are lumped together. Therefore, we could not distinguish purulent from nonpurulent infections. We also could not identify visits with incision and drainage (which would obviously indicate suspicion for

Discussion

We describe ED utilization and antibiotic choices during the period of emergence of community-associated MRSA, which is known to be important in purulent infections among ED patients.1 Analyzing 13 years of data from a representative sample of US EDs, we categorized visits according to whether they involved a skin and soft tissue infection and whether an antibiotic typically active against community-associated MRSA was chosen.

The data are consistent with our 2 hypotheses. From 1993 to 2005, we

References (13)

  • T. Kuriyama et al.

    Bacteriologic features and antimicrobial susceptibility in isolates from orofacial odontogenic infections

    Oral Surg Oral Med Oral Pathol Oral Radiol Endod

    (2000)
  • C.L. Ogden et al.

    The epidemiology of obesity

    Gastroenterology

    (2007)
  • G.J. Moran et al.

    Methicillin-resistant S aureus infections among patients in the emergency department

    N Engl J Med

    (2006)
  • M.N. Swartz

    Clinical practice: cellulitis

    N Engl J Med

    (2004)
  • L.F. McCaig et al.

    Plan and operation of the National Hospital Ambulatory Medical SurveySeries 1: programs and collection procedures

    Vital Health Stat 1

    (1994)
  • Centers for Disease Control and Prevention. [Centers for Disease Control and Prevention Ambulatory Care Drug Database...
There are more references available in the full text version of this article.

Cited by (389)

View all citing articles on Scopus

Supervising editor: David A. Talan, MD

Author contributions: All authors participated in conceptualization and planning of the analyses and manuscript preparation. AJP and JAE performed all analyses, and had full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis. DJP takes responsibility for the paper as a whole. None of the authors has any conflict of interest to declare.

Funding and support: By Annals policy, all authors are required to disclose any and all commercial, financial, and other relationships in any way related to the subject of this article, that might create any potential conflict of interest. The authors have stated that no such relationships exist. See the Manuscript Submission Agreement in this issue for examples of specific conflicts covered by this statement.

Publication dates: Available online January 25, 2008.

Reprints not available from the authors.

View full text