Use of an Enrichment Broth Improves Detection of Extended-Spectrum-Beta-Lactamase-Producing Enterobacteriaceae in Clinical Stool Samples

Abstract

cThis study evaluated the impact of preenrichment on the detection of extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBL-E) in clinical stool samples. ESBL-E were detected in 41 of 343 patients (12.0%). As 31.7% of the ESBL-E carriers were identified by preenrichment, only this additional diagnostic step significantly improved the detection of ESBL-E. E xtended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBL-E) are increasingly reported worldwide. Treatment options for infections due to these organisms are limited, and initial empirical therapy is often inappropriate and is associated with increased morbidity and mortality (1). ESBL-E carriers are known to develop bacteremia with the isolates colonizing the patients' intestines (2). Therefore, in many hospitals, risk-adapted screening for ESBL-E carriage is performed, but limited data exist on the optimal screening strategy. Currently, laboratory detection of ESBL-E in fecal specimens mostly relies on culture methods using selective agar medium. This method has a modest sensitivity (3). Preenrichment of swabs is used by many laboratories for methicillin-resistant Staphylococcus aureus (MRSA) screening and has demonstrated significantly improved sensitivity (4). To our knowledge, the impact of preenrichment on ESBL-E detection in stool samples has not been systematically investigated. In our study, we compared three different selective and nonselective broths for the detection of ESBL-E in clinical stool samples to the standard procedure-direct plating on ESBL agar.(This study was presented in part as a poster at the 25th European Congress of Clinical Microbiology and Infectious Diseases, Copenhagen, Denmark, 25 to 28 April 2015.) From September 2013 to March 2014, 496 stool samples submitted for ESBL-E screening from 343 patients at the University Hospital Cologne, a 1,400-bed tertiary care facility, were included in the study. All samples were stored at 4°C and were processed within 24 h of receipt. A pea-sized portion of solid stool or 250 l of liquid stool was suspended in 1 ml 0.9% NaCl to reach a standardized inoculum. One hundred microliters of the stool suspension was inoculated directly onto chromID ESBL agar (bioMérieux, Marcy l'Etoile, France) and into 5 ml of nonselective tryptic soy broth (TSB), MacConkey (MC) broth (Roth, Germany, Karlsruhe) selecting only Gram-negative rods, and MacConkey broth supplemented with cefuroxime (32 mg/liter) and vancomycin (64 mg/liter) (MC-CV) additionally inhibiting the nonresistant Gram-negative flora and further inhibiting Grampositive bacteria. Each medium was stored and processed according to the manufacturers' instructions.Agar plates and broths were incubated at 36°C Ϯ 1°C in ambient air for 18 h to 24 h. Using calibrated inoculation loops, 10 l of the respective enrichment broth was inoculated onto ESBL agar, which was incubated at 36°C Ϯ 1°C in ambient air for another 18 h to 24 h. Plates were interpreted according to the manufacturer's instructions. Uncolored colonies growing on ...

CTX-M ESBL-producing Enterobacteriaceae: estimated prevalence in adults in England in 2014

“…Faecal samples were screened for ESBLPE, using direct culture on selective medium (Brilliance ™ ESBL agar, Oxoid Ltd) for 24 h. To increase sensitivity, all samples were enriched as well as directly plated; 20 mg of each faecal sample was incubated for 24 h in 10 mL of brain heart infusion (BHI) broth containing 1 mg/L cefpodoxime 17 and subcultured onto Brilliance TM agar as before. 17 , 18 Oxidase-negative presumptive colonies of ESBLPE were defined as: +, 1–10 cfu; ++, 10–100 cfu; and +++, ≥100 cfu. One colony from each different colony morphology, from each plate of Brilliance agar, was identified using MALDI-TOF MS (Bruker UK Ltd) and tested for the bla CTX-M gene using multiplex PCR.…”

Multiplex Immunochromatographic Detection of OXA-48, KPC, and NDM Carbapenemases: Impact of Inoculum, Antibiotics, and Agar

“…All strains were analyzed for the presence of the bla OXA-48-like , bla VIM , bla IMP , bla NDM , bla GIM , and bla KPC carbapenemase genes by PCR and subsequent DNA Sanger sequencing, as previously reported (6,(8)(9)(10)(11). The MICs of ertapenem, meropenem, imipenem, and doripenem were determined using MIC test strips (Liofilchem, Roseto degli Abruzzi, Italy).…”

Antimicrobial resistant and extended‐spectrum β‐lactamase producing Escherichia coli in common wild bird species in Switzerland

“…(), we used a semi‐selective enrichment step prior to plating on selective ESBL agar, which may have affected the recovery rate. The difference in the performance of semi‐selective (using broth selecting for Gram negative rods) and selective enrichment (i.e., broth additionally containing a third‐generation cephalosporin) remains to be elucidated and comparative data are limited (Blane et al., ; Jazmati, Hein, & Hamprecht, ; Kluytmans‐Van Den Bergh et al., ).…”