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Control-group selection importance in studies of antimicrobial resistance: examples applied to Pseudomonas

Anthony D Harris1, Matthew H Samore, Marc Lipsitch

  • 1Department of Epidemiology and Preventive Medicine, University of Maryland School of Medicine, and VA Maryland Health Care System, Baltimore, MD, USA. aharris@epi.umaryland.edu

Clinical Infectious Diseases : an Official Publication of the Infectious Diseases Society of America
|May 29, 2002
PubMed

Insights

Choosing the right control group is crucial for accurate antimicrobial resistance risk factor analysis. Suboptimal control groups can lead to overestimated antibiotic risk, impacting treatment strategies.

Area of Science:

  • Medical Microbiology
  • Infectious Diseases
  • Clinical Epidemiology

Background:

  • Antimicrobial resistance is a growing global health threat.
  • Accurate identification of risk factors is essential for effective control strategies.
  • Control-group selection significantly influences the outcomes of risk factor analyses.

Purpose of the Study:

  • To evaluate the impact of different control-group selection methods on risk factor analysis for specific resistant organisms.
  • To compare the results obtained using two distinct control groups for imipenem-resistant Pseudomonas aeruginosa, vancomycin-resistant enterococci (VRE), and ampicillin-sulbactam-resistant Escherichia coli.

Main Methods:

  • Case-control study design.
  • Two types of control groups were used: Type 1 (patients with susceptible organisms) and Type 2 (patients from whom cases arose).
  • Risk factors for specific resistant infections were analyzed by comparing case patients with each control group.

Main Results:

  • Comparison with Type 1 controls identified different risk factors and odds ratios (ORs) compared to Type 2 controls for imipenem-resistant P. aeruginosa and ampicillin-sulbactam-resistant E. coli.
  • For VRE, vancomycin use was identified as a risk factor regardless of the control group, though ORs differed.
  • Type 1 controls tended to overestimate the OR for the resistance-defining antibiotic.

Conclusions:

  • The choice of control group critically affects the identification and magnitude of antibiotic risk factors for antimicrobial resistance.
  • Using susceptible organisms as controls (Type 1) may lead to inaccurate conclusions and overestimation of antibiotic-associated resistance.
  • Careful consideration of control-group selection is vital for reliable risk factor analysis in antimicrobial resistance research.

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