Chromid vre

For epidemiological surveillance, at the beginning of May 2017, the Hospital Infection and Prevention Control Department ordered a once-a-week rectal swab for routine screening of CR-GrN bacteria and VRE. Briefly, two separate rectal swabs were collected. For VRE detection, one swab was plated on ChromID^® VRE (bioMérieux, Brazil). For carbapenem-resistant enterobacterales and acinetobacter detection, the other swab was plated on CHROMagar mSuperCarba (Plastlabor, Brazil). Both plates were incubated in air at 35 ± 1 °C for a maximum of 48 h. If colonies were observed, identification was carried out using the Microflex mass spectrometry system (Bruker, Germany) (further details on Additional file 1).
Every Tuesday, all patients admitted for more than 48 h in the ICU were screened, excluding patients at end-of-life care. There was no routine screening for MDRB colonization outside ICU.
Between May 2017 and May 2019, we included all adult patients (≥ 18 years old), with active solid tumors or hematologic malignancies screened for CR-GrN bacteria and VRE during ICU stay. If a patient had multiple ICU admissions, only the first was considered. However, if a patient had multiple ICU admissions during the same hospital admission, and not the first, but a subsequent admission revealed CR-GrN bacteria or VRE colonization, that was the admission included in the study.

MDR screenings were carried out following the French national recommendations for healthcare settings [13 ]. Nasal and cutaneous swabs were used for the detection of MRSA and seeded on Chromid^® MRSA agar (Biomérieux, Marcy l’Etoile, France). Rectal swabs were used and seeded on Chromid^® Carba Smart agar (Biomérieux), Drigalski with ceftazidime agar (Becton Dickinson, Le-Pont-de-Claix, France), and Chromid^® VRE (Biomérieux) to detect CPE, ESBLE, and VRE, respectively. Identification of the MDR isolates was performed using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI Biotyper 2.2; Bruker Daltonik GmbH, Bremen, Germany). Carbapenemase production was ascertained using the Xpert^®carba-R kit (Cepheid, Sunnyvale, CA, USA) and/or the Resist-5 OOKNV^® immunoassay kit (Coris Bioconcept, Gembloux, Belgium)and/or the NG-test CARBA-5^® immunoassay kit (Eurobioscientific, Les Ullis, France) and/or the OXA-23 K-SeT^® immunoassay kit (Coris Bioconcept, Gembloux, Belgium). Typically, immunoassay kits were the first line of tests used for carbapenemase detection. The Xpert^® carba-Rkit was implemented for patients identified as returning from travel abroad or in case of doubtful results obtained with immunoassay kits. VanA/vanB genes were detected using the Xpert^® vanA/vanB kit (Cepheid).

All five selective agar commercially available in Germany at the time of the study were evaluated. They comprised of VRESelect™ (Bio-Rad, Hercules, CA, USA), CHROMagar™ VRE (CHROMagar, Paris, France), Brilliance™ VRE (Thermo Fisher, Dreieich, Germany), chromID^® VRE (bioMérieux, Marcy-l’Étoile, France) and Chromatic™ VRE (Liofilchem, Roseto degli Abruzzi, Italy).

For rectal screening of patients ESwab™ (COPAN Diagnostics INC., USA) was used. The liquid medium was inoculated on a chromogenic selective agar medium (ChromID VRE, bioMérieux, France). After incubation for 48 h at 35 ± 1 °C presumptive VRE colonies were confirmed by MALDI-TOF MS (VITEK® MS, bioMérieux, France) followed by multiplex polymerase chain reaction (PCR) artus® VanR QS-RGQ Kit (Qiagen, Hilden, Germany). Multilocus sequence typing (MLST) was performed as described [10 (link)], targeting seven housekeeping genes of E. faecium (atpA, ddl, gdh, purK, gyd, pstS adk). For editing, alignment, and phylogenetic analysis of sequences the MEGA 6.0 software package was used.

Stool samples for VRE testing were collected from 268 inpatients in sterile containers and were processed within 2 h after collection. Chromogenic agar medium (CHROMID®VRE, bioMerieux, France) was used for VRE screening. Stool samples were directly plated. In accordance with the manufacturers’ recommendations, plates were incubated at 36 ± 1 °C in ambient air, examined for growth after 24 h and 48 h and violet and blue-green colonies were presumptively identified as vancomycin resistant Enterococcus faecium (VREfm) or vancomycin resistant Enterococcus faecalis (VREfs), respectively. Three to four VRE colonies were inoculated into 1 mL of sterile Tryptic soy broth (TSB, Torlak, Serbia) and overnight cultures were microscopically examined for purity. Overnight cultures were placed in 10% glycerol and stored at − 72 ± 1 °C until future processing. Prior to testing, isolates were subcultured onto Columbia agar with 5% sheep blood (Torlak, Serbia).

The rectal swab was inoculated into 500 µl 0.9% NaCl suspension. Each culture media was inoculated with 20 µl suspension. Media used were Endo-Agar with Cefuroxim-disk, selective CHROMagar™ ESBL plates (Mast Diagnostica, Paris, France), chromID CARBA (bioMérieux, Nürtingen, Germany), chromID OXA-48 (bioMérieux), chromID VRE (bioMérieux), Brilliance MRSA-Agar (Oxoid, Wesel, Germany). When growth was detected, species identification was performed by matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) or biochemical reactions performed by VITEK2 (bioMérieux), additionally antibiotic susceptibility testing was performed according to Clinical and Laboratory Standards Institute (CLSI) guidelines M100-S24 (Version January 2014) by VITEK2 (bioMérieux), agar diffusion (Oxoid) or antibiotic gradient tests (Liofilchem, Roseto degli Abruzzi, Italy).

Screening for VRE was performed using deep rectal swabs or stool samples plated on selective media (chromID VRE, bioMérieux, Nürtingen, Germany) and incubated for up to 48h. Colonies were identified to species level using mass spectrometry (matrix-assisted laser desorption/ionization time-of-flight, MALDI-TOF), and antimicrobial susceptibility testing was performed using Vitek2 AST P592 cards (bioMérieux) complemented by E-test (bioMérieux) in cases of minimal inhibitory concentrations (MICs) for vancomycin ≥ 4mg/L. In accordance with the European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints, isolates with an MIC value > 4mg/L were considered resistant [17 ].