Risk factors associated with vancomycin-resistant enterococcal colonization in a general ICU and the effect of surveillance and prevention over respiratory tract and nosocomial infections

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Objectives

• 1) To determine the risk factors associated with vancomycin-resistant enterococcal (VRE) colonization in a general ICU. 2) To observe the effect of infection control measures over respiratory tract and nosocomial infections in that unit.

Design

Point-prevalence surveys for VRE colonization of patients were carried out over the period from March 1998 to June 1998.

Setting

General medical and surgical ICU in a tertiary teaching hospital in the city of São Paulo, Brasil.

Measurements

The first case of VRE colonization in the unit was related in March 1998. Point-prevalence surveys were then carried out to evaluate the main risk factors related to VRE colonization (enteral feeding, severity of illness, length of ICU stay, colonization pressure, antimicrobial use, and others). A univariate analysis was made and the variables that demonstrated P≤ 0.10 were then entered into a discriminant analysis to identify the β coefficients.

Measures against VRE colonization were established based on CDC criteria (MMWR 44(RR12);1–13) and the effects of these measures over the respiratory tract infection rate and the nosocomial infection rate according to the NNIS (National Nosocomial Infections Surveillance) system were measured. Strain typing was characterized using pulsed-field gel electrophoresis (PFGE).

Main results

Thirty-eight patients were evaluated. 18 VRE and 11 vancomycin-susceptible enterococcal (VSE) colonizations were identified in anal swab, wound and venous catheter. Out of 18 enterococcal strains isolated, 13 strains were E. faecium, distributed in 5 different groups according to PFGE. The other 5 strains were E. fecalis, distributed in 4 groups according to PFGE as well.

The results concerning the univariate analysis and the discriminant analysis (Table 1), the respiratory tract infection rates and the nosocomial infection rates (Table 2) are given.

Conclusions

The colonization pressure, vancomycin use and length of ICU stay ≥ 29 days were the main risk factors associated with VRE colonization.

Measures against VRE colonization resulted in a significant decrease in the respiratory and nosocomial infection rates. This decrease was probably due to reduction of other pathogens colonization pressure.

Table 1 Table 1

Table 2 Table 2