Using VRE screening tests to predict vancomycin resistance in enterococcal bacteremia

Abstract

Background and objective:Enterococcus causes clinically significant bloodstream infections (BSIs). In centers with a higher prevalence of vancomycin resistant enterococcus (VRE) colonization, a common clinical question is whether empiric treatment directed against VRE should be initiated in the setting of a suspected enterococcal BSI. Unfortunately, VRE treatment options are limited, and relatively expensive, and subject patients to the risk of adverse reactions. We hypothesized that the results of VRE colonization screening could predict vancomycin resistance in enterococcal BSI.Methods:We reviewed 370 consecutive cases of enterococcal BSI over a 7-year period at 2 tertiary-care hospitals to determine whether vancomycin-resistant BSIs could be predicted based on known colonization status (ie, patients with swabs performed within 30 days, more remotely, or never tested). We calculated sensitivity and specificity, and we plotted negative predictives values (NPVs) and positive predictive values (PPVs) as a function of prevalence.Results:A negative screening swab within 30 days of infection yielded NPVs of 90% and 95% in settings where <27.0% and 15.0% of enterococcal BSI are resistant to vancomycin, respectively. In patients with known VRE colonization, the PPV for VRE in enterococcal BSI was >50% at any prevalence exceeding 25%.Conclusions:The results of a negative VRE screening test result performed within 30 days can help eliminate unnecessary empiric therapy in patients with suspected enterococcal BSI. Conversely, patients with positive VRE screening swabs require careful consideration of empiric VRE-directed therapy when enterococcal BSI appears likely.

Impact of a vancomycin-resistant Enterococcus (VRE) screening result on appropriateness of antibiotic therapy

“…This study reported a PPV of >50% for VRE proportion >25% and NPV of 90% and 95% for a VRE proportion <27% and <15%, respectively. 16 A prospective study of ICU patients found that twice-weekly screening had a sensitivity of 89%, specificity of 90%, PPV of 44%, and NPV of 99%. 19 Univariate and multivariate analyses demonstrated that patients in our cohort who received intravenous or oral vancomycin or antipseudomonal antibiotics, had renal dysfunction, or with a history of solid-organ transplantation were more likely to develop VRE infection.…”

“…Previous studies have demonstrated that a negative VRE screening result has a high specificity and negative predictive value (NPV) for the development of a VRE infection, but the correlation between a positive screen and subsequent VRE infection has yet to be determined. [14][15][16]…”

VanA rectal swab screening as a predictor of subsequent vancomycin-resistant enterococcal bloodstream infection in critically ill adults

“…In this study, vanA and vanB rectal swabs were performed in a targeted population with history of or at high risk of MDR organisms, likely enhancing the swab predictive ability; however, only 4% of rectal swabs were positive, with 2% of included patients having a VRE BSI. Butler-Laporte et al 10 conducted a retrospective cohort study in a mixed population of 241 enterococcal BSI and most recent vanA and vanB screen of the rectum, stool or colostomy collected within 30 days prior to the BSI. A 73.7% sensitivity and 82.2% specificity were reported; however, patient-level data, time between swab and culture, and predictive values for the ICU population were not described.…”

“…The primary objective of this study was to determine the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of a vanA rectal swab collected within 14 days of an enterococcal BSI to predict VRE BSI. 10,13 Secondary objectives were to evaluate these end points in 3 subgroups: (1) if the vanA rectal swab was collected within 7 days of an enterococcal BSI; (2) if the vanA rectal swab was collected within 3 days of an enterococcal BSI; (3) which patients were in the cohort of immunocompromised patients with a vanA rectal swab collected within 14 days of an enterococcal BSI; and (4) the impact of a positive vanA rectal swab on empiric antimicrobial therapy selection, defined as therapy initiated or active from time of blood culture collection to blood culture result availability.…”

“…[6][7][8] Similar to studies evaluating the clinical utility of MRSA nasal swabs, 9 studies in hospitalized and immunocompromised cohorts have evaluated the ability of polymerase-chain reaction (PCR)-based rectal swab to identify VRE-colonized patients and subsequently predict VRE infections. [10][11][12] In these studies, it has been challenging to extrapolate to critically ill patients due to low rates of subsequent enterococcal infections, low patient acuity, or an extended duration between rectal swab collection and the enterococcal infection. The purpose of this study was to determine the predictive ability of a vanA rectal swab in critically ill adults with an enterococcal BSI.…”