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Updated: Jun 1, 2026
Subcutaneous Infection of Methicillin Resistant Staphylococcus Aureus (MRSA)
Published on: February 9, 2011
Colonization pressure adjusted by degree of environmental contamination: a better indicator for predicting
Junrui Wang1, Mei Wang, Yanfei Huang
1Clinical Laboratory, Beijing Tongren Hospital, Capital Medical University, China.
Background:
Colonization pressure has been confirmed as an important risk factor for methicillin-resistant Staphylococcus aureus (MRSA) acquisition among inpatients, but their precise relationship has not been well investigated. Because MRSA carriers can disperse MRSA into their immediate environment with different abilities, the relationship among colonization pressure, the degree of MRSA contamination in environment surrounding MRSA carriers, and MRSA transmission should be explored to facilitate efficient implementation of infection control measures.
Methods:
Active MRSA screening and environmental sampling were performed in a 23-bed emergency ward (EW) and a 7-bed respiratory intensive care unit (RICU) between March 2009 and February 2010. Weekly colonization pressure (WCP) was modified to WCPe (WCP adjusted by degree of environmental contamination). Receiver operating characteristic curve and correlation analyses were used to analyze the accuracy of WCPe in predicting MRSA acquisition and their correlation, respectively.
Results:
We found that 34.1% (858/2,520) of the immediate environmental sites of MRSA-positive patients were contaminated with MRSA. The areas under the receiver operating characteristic curve of WCPe reached as high as 0.784 (95% confidence interval, 0.659-0.909; P < .01) for the EW and 0.866 (95% confidence interval, 0.766-0.967; P < .01) for the RICU. Spearman's correlation coefficient (r) indicated a positive and significant correlation between WCPe and MRSA acquisition rate in the subsequent weeks for both the EW (r = 0.45; P = .001) and RICU (r = 0.51; P < .001).
Conclusion:
Active MRSA screening combined with targeted environmental contamination monitoring could be a more efficient measure for determining the magnitude of the MRSA reservoir in wards occupied by MRSA carriers. WCPe showed moderate prediction accuracy for both the EW and the RICU, and a threshold WCPe value may be used as a predictor to enhance infection control measures, especially for medical facilities without a sufficient number of single rooms.
Insights
Environmental contamination by methicillin-resistant Staphylococcus aureus (MRSA) is linked to patient acquisition. Modified colonization pressure (WCPe), accounting for environmental MRSA levels, accurately predicts MRSA spread in hospitals.
Area of Science:
- Infectious Disease Epidemiology
- Hospital Infection Control
- Microbiology
Background:
- Colonization pressure is a known risk factor for methicillin-resistant Staphylococcus aureus (MRSA) acquisition in inpatients.
- The precise relationship between colonization pressure, environmental contamination, and MRSA transmission requires further investigation for effective infection control.
Purpose of the Study:
- To explore the relationship between colonization pressure, environmental MRSA contamination, and MRSA transmission.
- To develop and validate a modified colonization pressure metric (WCPe) for predicting MRSA acquisition.
Main Methods:
- Active MRSA screening and environmental sampling in an emergency ward (EW) and a respiratory intensive care unit (RICU).
- Development of weekly colonization pressure adjusted by environmental contamination (WCPe).
- Analysis of WCPe accuracy in predicting MRSA acquisition using ROC curves and correlation analyses.
Main Results:
- 34.1% of immediate environmental sites near MRSA-positive patients were contaminated.
- WCPe demonstrated significant predictive accuracy for MRSA acquisition in both EW (AUC=0.784) and RICU (AUC=0.866).
- A significant positive correlation was observed between WCPe and subsequent MRSA acquisition rates in both units.
Conclusions:
- Active MRSA screening combined with environmental monitoring offers an efficient approach to assess the MRSA reservoir.
- WCPe shows moderate predictive accuracy and can be utilized as a threshold to enhance infection control, particularly in facilities lacking single rooms.
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