THE ROLE OF COLONIZATION PRESSURE IN THE SPREAD OF VANCOMYCIN-RESISTANT ENTEROCOCCI - AN IMPORTANT INFECTION-CONTROL VARIABLE

Objective: The spread of nosocomial multiresistant microorganisms is a ffected by compliance with infection control measures and antibiotic u se. We hypothesized that ''colonization pressure'' (ie, the proportion of other patients colonized) also is an important variable. We studie d the effect of colonization pressure, compliance with infection contr ol measures, antibiotic use, and other previously identified risk fact ors on acquisition of colonization with vancomycin-resistant enterococ ci (VRE). Methods: Rectal colonization was studied daily for 19 weeks in 181 consecutive patients who were admitted to a single medical crea ted using a Cox proportional hazards regression model including length of stay in the medical intensive care unit until acquisition of VRE, colonization pressure, personnel compliance with infection control mea sures (hand washing and glove use), APACHE (Acute Physiology and Chron ic Health Evaluation) II scores, and the proportion of days that a pat ient received vancomycin or third-generation cephalosporins, sucralfat e, and enteral feeding. Results: With survival until colonization with VRE as the end point, colonization pressure was the most important va riable affecting acquisition of VRE (hazard ratio [HR], 1.032; 95% con fidence interval [CI], 1.012-1.052; P=.002). In addition, enteral feed ing was associated with acquisition of VRE (HR, 1.009; 95% CI, 1.000-1 .017; P=.05), and there was a trend toward association of third-genera tion cephalosporin use with acquisition (HR, 1.007; 95% CI, 0.999-1.01 5; P=.11). The effects of enteral feeding and third-generation cephalo sporin use were more important when colonization pressure was less tha n 50%. Once colonization pressure was 50% or higher, these other varia bles hardly affected acquisition of VRE. Conclusions: Acquisition of V RE was affected by colonization pressure, the use of antibiotics, and the use of enteral feeding. However, once colonization pressure was hi gh, it became the major variable affecting acquisition of VRE.