Abstract & Commentary: Does VRE matter? You bet your life
April 1, 2002 3 minutes read
Abstract & Commentary: Does VRE matter? You bet your life
A Rodney Dangerfield’ bug finally gets respect
Synopsis: VRE bacteremia is an independent predictor of death, and appropriate antibiotic therapy is associated with improved survival.
Source: Vergis E, et al. Determinants of vancomycin resistance and mortality rates in enterococcal bacteremia. A prospective multicenter study. Ann Intern Med 2001; 135:484-492.
Abstract: The authors performed a prospective observational study of patients with enterococcal bacteremia at four academic medical centers and one community hospital in order to determine whether vancomycin resistance is an independent predictor of death as well as whether outcome is affected by appropriate antibiotic therapy.
Sixty percent of the 398 bloodstream isolates were Enterococcus faecalis and 37% E. faecium; 35% of the 398 were vancomycin-resistant (VRE; MIC > 32 µg/mL), while 2% were intermediate (MIC 8-16 µg/mL). Eight percent of E. faecalis and 80% of E. faecium were vancomycin-resistant. Eighty-seven percent of E. faecium were resistant to ampicillin, 60% had high-level gentamicin resistance, and 22% had reduced susceptibility to quinupristin/dalfopristin. Linezolid was not tested in the study.
Thirty-eight percent of the 147 patients with VRE bacteremia and 49% of those with susceptible enterococcal bacteremia had more than one organism recovered in blood culture. Infection at an abdominal site other than the biliary tract was four times more common (20% vs. 4%) in the patients with VRE bacteremia compared to those with susceptible isolates.
Vascular catheters were the most common site of infection in the former group and the second most common site in the latter. Endocarditis was present in 3% of patients in each group.
Multivariate analysis found that the independent risk factors for VRE bacteremia were receipt of vancomycin within the previous 14 days, receipt of glucocorticosteroids within the previous 14 days, and the severity of illness (APACHE II score). Risk factors for death within 14 days were the presence of an underlying hematologic malignancy, vancomycin resistance, and severity of illness.
Bacteriological failure was more common with VRE infection (12/16 vs. 4/16). In a multivariate analysis restricted to 208 patients with monomicrobial VRE bacteremia, APACHE II score was a risk factor for 14-day mortality, while receipt of appropriate antibiotic therapy within 48 hours of the initial positive blood culture was protective.
Comment by Stan Deresinski, MD, FACP
This study addresses a central question related to VRE, the answer to which had previously remained uncertain: Does VRE matter? Previous studies have resulted in varying answers. For instance, a case control study identified VRE bacteremia as being associated with greater all-cause mortality than was bacteremia with vancomycin-susceptible strains.1
However, other studies have found that, although patients with VRE bacteremia do, indeed, have greater overall mortality, vancomycin resistance is not an independent predictor of mortality and is more likely simply a marker of the severity of comorbidity.2
The paper under review authoritatively answers the question of the relevance of VRE bacteremia in the affirmative. They have demonstrated that VRE bacteremia and lack of effective antibiotic therapy active against VRE in patients with bacteremia are each independent risk factors for mortality.
These observations have important implications. First, vigorous attempts to prevent patient acquisition of VRE are warranted. This means implementation of effective infection control practices to limit the spread of VRE and control of use of relevant antibiotics that predispose to colonization with VRE, especially vancomycin. It also means that strong consideration be given to screening of high-risk patients for colonization with VRE.
The results of this study also demonstrate that a low threshold for administration of antibiotics likely to be active against VRE must be maintained in the appropriate settings. Thus, in institutions in which VRE are prevalent, the presence of organisms morphologically compatible with enterococci observed on Gram staining of blood culture should trigger the use of an antibiotic likely to be effective against VRE, at least until definitive microbiological data are available. This is likely to be a policy unpopular with those responsible for the pharmacy budget, since the antibiotic most reliably active against VRE is linezolid.
In 2000, the average wholesale cost of a 600 mg vial of linezolid was $72 and that of a 600 mg tablet was $53.3
Dr. Deresinski is Associate Professor of Medicine, Stanford (CA) University, is editor of Infectious Disease Alert, a sister publication to Hospital Infection Control.
References
1. Bhavnani SM, et al. Diagn Microbiol Infect Dis 2000; 36:145-158.
2. Lautenbach E, et al. Infect Control Hosp Epidemiol 1999; 20:318-323.
3. Medical Letter 2000; 42:45-46.
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