c Overall, 2,337 rectal screening samples (RSSs) were seeded by using the Wasp instrument for automated microbiological processing with five media for detection of extended-spectrum ␤-lactamase (ESBL): CHROMagar, ChromID, Brilliance, BD Drigalski, and HEGP media. Of 354 RSSs harboring ESBL-producing isolates, 89.3% were found to be positive on all media. Sensitivity and specificity ranged from 95.5 to 98.3% and from 57.9 to 72.3%, respectively. No medium was perfectly ESBL selective, and non-ESBL-producing strains were mainly Enterobacteriaceae overproducing AmpC ␤-lactamase and nonfermenting Gram-negative bacilli, mostly Pseudomonas aeruginosa. In recent years, a dramatic increase in the prevalence of Enterobacteriaceae producing extended-spectrum ␤-lactamases (ESBLs) has been observed in Europe (1-3). In order to prevent nosocomial cross-transmission, systematic detection of carriage of ESBL-producing bacteria in the digestive tract of high-risk patients has been recommended by various academic societies (4, 5). In this context, hospital microbiology laboratories face several challenges. Systematic screening leads to an increased number of samples to be tested, while at the same time, budget restrictions entail reductions in human resources. Automation can be a relevant means of analyzing a large number of samples (6-9), but the delay in obtaining results still needs to be reduced. Moreover, if molecular tests for ESBL detection are expected to give a faster result than culture, the cost of these tests for large series is currently still too high relative to that of traditional culture. In this situation, agar manufacturers have improved their media for detection of ESBLs after only 24 h (10-16). Taking advantage of the Wasp instrument, an automated device for microbiological specimen processing, planting, and streaking (Copan, Brescia, Italy), we decided to compare the efficiencies of five selective media designed for ESBL detection.The study was conducted at Hôpital Européen Georges-Pompidou (HEGP), an 830-bed acute-care teaching hospital with 23 wards and with 29,000 admissions in 2011. A rectal screening sample (RSS) was collected daily from each patient admitted to the intensive care units (ICUs) between 3 April and 3 July 2011, in compliance with French patient confidentiality regulations and ethical standards. The study was approved by an institutional review board (CCPPRB project no. ID-RCB 2011-A00259-32, University Paris XI, February 2011). Sampling was done by using the eSwab system (Copan). The swab sample was suspended in 1 ml of liquid Amies medium (Copan), and 10 l was streaked by the automated system onto two sets of media, including (i) five media for the detection of ESBL, i.e., CHROMagar ESBL (CHROMagar, Paris, France), ChromID ESBL (bioMérieux, Lyon, France), Brilliance ESBL (Oxoid, Basingstoke, United Kingdom), BD Drigalski lactose agar with ceftazidime (Becton, Dickinson, Franklin Lakes, NJ), and in-house-made "HEGP medium" containing Drigalski agar (Oxoid, Basingstoke, Great Britain) and...

There is no consensus on optimal screening procedures for multidrug-resistant Enterobacteriaceae (MDRE) in intensive care units (ICUs). Therefore, we assessed five strategies for the detection of extended-spectrum beta-lactamase (ESBL) and high-level expressed AmpC cephalosporinase (HL-CASE) producers. During a 3-month period, a rectal screening swab sample was collected daily from every ICU patient, from the first 24 h to the last day of ICU stay. Samples were plated on MDRE-selective media. Bacteria were identified using MALDI-TOF mass spectrometry and antibiograms were performed using disk diffusion. MDREs were isolated from 682/2348 (29.0%) screening samples collected from 93/269 (34.6%) patients. Incidences of patients with ESBL and HL-CASE producers were 17.8 and 19.3 per 100 admissions, respectively. In 48/93 patients, MDRE carriage was intermittent. Compared with systematic screening at admission, systematic screening at discharge did not significantly increase the rate of MDRE detection among the 93 patients (62% vs. 70%). In contrast, screening at admission and discharge, screening at admission and weekly thereafter, and screening at admission and weekly thereafter and at discharge significantly increased MDRE detection (77%, p 0.02; 76%, p 0.01; 86%, p<0.001, respectively). The difference in MDRE detection between these strategies relies essentially on the levels of detection of patients with HL-CASE producers. The most reasonable strategy would be to collect two samples, one at admission and one at discharge, which would detect 87.5% of the ESBL strains, 67.3% of the HL-CASE strains and 77.4% of all MDRE strains. This study should facilitate decision-making concerning the most suitable screening policy for MDRE detection in a given ICU setting.