Objectives: To determine the validity of an active, hospital laboratory isolate-based surveillance system in estimating rates of infection and to evaluate the use of surveillance data in describing institutional risk factors for increased rates of infection. Methicillin-resistant Staphylococcus aureus (MRSA) was chosen as the prototype organism for these evaluations.
Design: Correlation Study: linear regression analysis and Student's t test were used to evaluate the correlation between number of MRSA isolates and number of MRSA infections in acute-care hospitals. Cross-Sectional Study: Student's t test, analysis of variance, and multiple linear regression analysis were used to evaluate the association between mean annual rate of MRSA blood isolates and institutional risk factors for increased rates of infection.
Setting: Acute-care hospitals, New Jersey.
Results: The number of MRSA blood isolates was significantly correlated with MRSA blood infections (R, 0.78; P < .01) and provided a good proxy measure for number of infections. Multivariate analysis demonstrated hospital location in the inner city (P = .02) and number of occupied beds (P < .01) to be independently associated with increased mean annual rates of MRSA blood isolates in acute-care hospitals.
Conclusions: This surveillance system is a valid tool for the estimation of institutional rates of infection and for the determination of institutional risk factors for increased rates of infection. It is ideal for further population-based investigations of antimicrobial-resistant bacteria.