Quantitative Spatial Analysis of Nosocomial Methicillin-Resistant Staphylococcus aureus (MRSA) and Clostridium difficile in Pennsylvania Hospitals

Open Access
Smith, Wilton Prescott
Area of Honors:
Interdisciplinary in Biology and Health Policy and Administration
Bachelor of Science
Document Type:
Thesis Supervisors:
  • Ottar N Bjornstad, Thesis Supervisor
  • Sarah Mary Assmann, Honors Advisor
  • Rhonda BeLue, Honors Advisor
  • Hospital-Acquired Infections
  • Nosocomial Infections
  • Epidemiology
  • MRSA
  • C. diff
  • Disease Dynamics
Nosocomial infections, also known as hospital-acquired infections, are infections caused by pathogens contracted in the hospital environment. It is possible that nosocomial infections are greater than a hospital-level problem, as factors about a hospital’s catchment population and geographic region could confer epidemiological risk (1). This research examines population and spatial effects on infection rates of Methicillin-Resistant Staphylococcus aureus (MRSA) and Clostridium difficile (C. diff) in 165 Pennsylvania hospitals. Infection rates were obtained from the CDC’s Hospital Compare dataset, and standardized based on patient days (2). Standardized infection rates were regressed against hospital size, as well as county-level socioeconomic data from the Area Health Resource File (AHRF) to assess catchment population trends (3). Hospitals were also compared by spatial autocorrelation analysis, and by local indicators of spatial association (LISA) (4,5). Finally, infection rates of MRSA and C. diff were compared by regression and spatial cross-correlation. This analysis finds that the size of a hospital has a significant positive effect on both the presence of infection and the rate of infection in that hospital. Concerning spatial risk, clustering of MRSA occurs in urban areas, with significant positive spatial autocorrelation observed out to a distance of 43 km. However, spatial analysis of C. diff shows inconclusive evidence of regional influence. Further, the infection rates of MRSA and C. diff are significantly correlated on a hospital-by-hospital basis, but are not correlated spatially. Thus, the conclusion from this research is that both hospital-level and regional-level factors likely contribute to these nosocomial infection rates.