Optimal detection of extended-spectrum ß-lactamase producers, carbapenemase producers, polymyxin-resistant Enterobacterales, and vancomycin-resistant enterococci from stools.

ABSTRACT

This study compared the impact of different approaches, namely, nonenrichment, nonselective enrichment, and selective (antibiotic-containing) enrichment steps, for detecting extended-spectrum ß-lactamase producing Enterobacterales (ESBL-E), carbapenemase-producing Enterobacterales (CPE), polymyxin-resistant Enterobacterales (PMR-E), and vancomycin-resistant enterococci (VRE) from spiked stools. The use of a nonselective 18-h enrichment broth culture significantly improved the recovery rate of all types of resistant bacteria after their plating onto selective media. In addition, the detection of ESBL-E, CPE, PMR-E, and VRE was further improved when using an enrichment step using antibiotic-supplemented broths respectively supplemented with cefotaxime (0.1 µg/mL), ertapenem (0.1 µg/mL), colistin (0.5 µg/mL), and vancomycin (1 µg/mL). Therefore, we showed here that a screening strategy based on a selective broth enrichment step significantly contributes to an increased rate of detection of multidrug-resistant bacteria, which may be crucial in term of improvement of infection control.