Detection of Vancomycin‐Resistant Enterococci Before and After Antimicrobial Therapy: Use of Conventional Culture and Polymerase Chain Reaction

Abstract

Antimicrobial therapy can increase the colonization density of gastrointestinal vancomycin-resistant enterococci (VRE). Among previously VRE-colonized patients, we evaluated VRE colonization before and after initiation of antimicrobial therapy by means of polymerase chain reaction (PCR) and culture. Perianal swab samples were obtained at admission to the hospital and after receipt of antimicrobial therapy. At admission, 12 (21%) of 56 patients were culture positive, and 17 (30%) had vanA or vanB genes detected by PCR. Culture results showed that 25 (86%) of 29 culture-negative patients from whom a second swab sample was obtained remained culture negative, 2 (6.9%) had a relapse of colonization with a strain related to the previously colonizing strain type (2 and 6 days after admission), and 2 (6.9%) tested positive for a previously undetected strain type (16 and 19 days after admission). PCR at admission detected VRE in 1 of the 2 patients who later relapsed. Patients with negative results of culture of the initial swab sample and of PCR were unlikely to relapse after receipt of antimicrobial therapy.

Failure to Develop Vancomycin-Resistant Enterococcus With Oral Vancomycin Treatment of Clostridium difficile

“…These data support those of the current study by showing that patients not presently colonized, as detected by culture or PCR, were significantly less likely to become culture positive with antibiotic therapy than were those who retained colonization as documented by PCR testing. 47 Antibiotics may alter the protective effect of the endogenous gastrointestinal flora against colonization by VRE 48 and thus may increase the likelihood of colonization with VRE when an exposure occurs. Also, eradication of the normal flora may allow subpopulations of VRE to overgrow and achieve higher stool densities.…”

Characterizing an outbreak of vancomycin-resistant enterococci using hidden Markov models

“…Literature sources regarding the sensitivity of rectal swabs in detecting VRE were used to develop an expression for the uncertainty in this parameter. Estimates of the sensitivity of a rectal swab for VRE range from 0.58 (D'Agata et al 2002) to 0.97 (Reisner et al 2000) with values in between (Lemmen et al 2001;Trick et al 2004). We allowed for the uncertainty regarding the detection by assigning a uniform [0.58, 0.97] prior distribution to d. The probability of detection at a given prevalence check, d, used in this study was patient related rather than simply swab related.…”

Evaluation of Spectra VRE, a New Chromogenic Agar Medium Designed To Screen for Vancomycin-Resistant Enterococcus faecalis and Enterococcus faecium

“…The rapid strain identification for patients colonized in the gastrointestinal tract with vancomycin-resistant strains of these species (VRE) is critical, as infection with these organisms can result in endocarditis, urinary tract, bloodstream, and wound infections with reduced therapeutic options (3). Screening for VRE is essential for the proper implementation of isolation precautions, as asymptomatic carriers serve as reservoirs for VRE infection or transmission (4,7,9). Successful identification of patients colonized with VRE requires rapid and accurate screening tests that are easily interpretable.…”