EMERGEncy ID Net Study

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Moran GJ, et al. "Methicillin-Resistant S. aureus Infections among Patients in the Emergency Department". The New England Journal of Medicine. 2006. 355(7):666-674.
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Clinical Question

Among ED patients with skin and soft tissue infections, what is the prevalence of community-acquired methicillin resistant staphylococcus aureus (MRSA)?

Bottom Line

Community acquired MRSA has become far more prevalent in patients with skin & soft tissue infection and if patients present with possible risk factors for MRSA, care must be taken in selecting empiric antibiotics to ensure concordance with susceptibilities.

Major Points

Antibiotic resistance has been an emerging problem and we may be entering the post-antibiotic era as common pathogens accumulate resistance to different classes of medications.[1] In this 2006 survey of American EDs, 422 patiens with skin and soft tissue infections were found to have Staphylococcus aureus isolated on cultures. Of these, 59% (range 15-74%) were community acquired MRSA. Susceptibilities to clindamycin, rifampin, and trimethoprim-sulfamethoxazole were all greater than 90% and the clindamycin inducibility was uncommon. Prevalence and susceptibilities was variable depending on region. Almost 60% of the time, empiric antibiotics prescribed in MRSA positive cases were not concordant but this had no affect on clinical outcomes.

This study helped define some of the risk factors for community-acquired MRSA status, including antibiotic use in the past month, presence of an abscess, report of a 'spider bite', prior MRSA infection, and close contact with someone with a similar infection. On multivariate logistic regression, non-Hispanic Black race, use of any antibiotic in the past month, report of 'spider bite', prior MRSA infection, and close contact with someone with a similar infection were associated with increased risk of community-acquired MRSA infection.

Guidelines

Practice Guidelines for the Diagnosis and Management of Skin and Soft Tissue Infections: 2014 Update by the Infectious Diseases Society of America[2]

Moderate purulent infection
  • Incision and drainage + antibiotics
    • Empiric antibiotic options: Trimethoprim-sulfamethoxazole or doxycycline
    • Defined antibiotics:
      • MRSA: Trimethoprim-sulfamethoxazole
      • MSSA: Dicloxacillin or cephalexin
Severe purulent infection
  • Incision and drainage + antibiotics
    • Empiric antibiotics: Vancomycin, daptomycin, televancin, linezolid, ceftaroline
    • Defined antibiotics:
      • MRSA - See empiric antibiotics
      • MSSA - Naficillin, clindamycin, cefazolin

Design

  • Multicenter, cross-sectional study
  • N = 422
  • Setting: 11 university-affiliated emergency departments, members of the EMERGEncy ID Net
  • Enrollment: August 2004
  • Analysis: Descriptive statistics
  • Primary outcome: Staphylococcus aureus susceptibility
  • Secondary outcomes:
    • Rick factors for MRSA infection
    • Inducibility of clindamycin resistance determined by the D-zone disk-diffusion test
    • Presence of genes for:
      • Staphylococcal enterotoxins A through E and H
      • Toxic shock syndrome toxin 1 (TSST-1), and
      • Panton–Valentine leukocidin (pvl) and the type of SCCmec were determined by PCR

Population

Inclusion Criteria

  • >18 years or older
  • Purulent skin/soft-tissue infection <1 week's duration

Exclusion Criteria

  • Perirectal abscess

Baseline Characteristics

  • Median age 39 years (range 18-79; IQR 28-47)
  • 62% male
  • Ethnicity:
    • 49% non-Hispanic Black
    • 25% non-Hispanic White
    • 22% Hispanic
    • 4% other groups
  • Site of infection
    • 29% upper extremities
    • 27% lower extremities
    • 17% torso
    • 14% perineum
    • 13% neck
  • Infection Classification
    • 81% abscess
    • 11% infected wound
    • 8% cellulitis with purulent exudate

Interventions

  • Analysis of cultures with multiple modalities testing for sensitivities and pathogenic features

Outcomes

Comparisons are MRSA vs. MSSA, unless otherwise stated

Primary Outcomes

S. aureus prevalence in presenting skin/soft tissue infection patients (N=422)
320 (76%)
S. aureus susceptibility in isolates (N=320)
249 (78%) vs. 71 (22%)
MRSA prevalence of isolates based on infection site
Abscess: 61%
Purulent wounds: 53%
cellulitis with purulent exudate: 47%
MRSA Susceptibilities
Trimethoprim-sulfamethoxazole 217/217(100%)
Rifampin: 186/186(100%)
Clindamycin 215/226(95%)
Tetracycline: 207/226(92%)
Fluoroquinolones: 106/176(60%)
Erythromycin: 13/226(6%)

Secondary Outcomes

Multivariate Logistic-Regression Analysis for Risk Factors for MRSA Infection Adjusted Odds Ratio (95% CI)
Non-Hispanic black: 1.9 (1.1–3.4)
Use of any antibiotic in past month (vs. no use): 2.4 (1.3–4.3)
Reported spider bite (vs. other cause of infection): 3.0 (1.6–5.7)
Underlying illness (vs. no underlying infection): 0.3 (0.2–0.6)
History of MRSA infection (vs. absence of such history): 3.4 (1.1–10)
Close contact with person with similar infection (vs. no close contact): 3.8 (1.6–9.3)
Samples provided to the CDC
218 (88%) vs 55 (77%)
Characterization of pulsed-field types of isolates (n=218)
Community Associated MRSA 216/218 (99%)
USA300: 212 (98%) vs. 17 (31%)
USA300-0114: 156 (74%) vs. 8 (47%)
USA400: 2 (1%)
USA1000: 2 (1%)
SCCmec type IV
214 (98%)
pal toxin gene presence in isolates
213 (98%) vs. 23 (42%)
Inducible clindamycin resistance by D-zone disk-diffusion test
4(2%) vs. 5(9%)

Subgroup Analysis

Treatment (n=406)
Incision and Drainage alone 79(19%)
Antibiotics alone 39(10%)
Both I&D and Antibiotics 267(66%)
Neither I&D or Antibiotics 21(5%)
Discordant Antibiotic Treatment of MRSA
100/175(57%)

Criticisms

  • Prevalence trial
  • Despite this, unclear about clinical outcomes
  • Reporting antibiotic concordance following I&D+Antibiotics vs Antibiotics alone would have allowed a better understanding of potential failure rate

Funding

  • Supported by a cooperative agreement (U50/CCU912342) with the CDC
  • Multiple stated conflicts of interest from the authors, receiving research, lecture, or advisory board funding from Schering-Plough, Pfizer, Aventis, Ortho-McNeil, and Cubist.

Further Reading

  1. Draenert R et al. Novel antibiotics: are we still in the pre-post-antibiotic era?. Infection 2015. 43:145-51.
  2. 2014 IDSA guidelines