Computational techniques for fluid dynamics 2 - Specific techniques for different flow categories

Abstract

The ability of the Carba NP test to detect carbapenemase-producing Enterobacteriaceae that have been isolated on different culture media was evaluated. A panel of carbapenemase-producing (n=50) and non-carbapenemase-producing Enterobacteriaceae (n=12) was cultured on (i) three non-selective media (blood agar, tryticase soy agar, UriSelect™ 4), (ii) two Gram-negative bacilli selective media (Drigalski agar, McConkey agar), (iii) Mueller-Hinton agar plates from four manufacturers (bioMérieux, Bio-Rad, Becton-Dickinson, Oxoid), and (iv) three screening media aimed to detect extended-spectrum ß-lactamase producers or carbapenemase producers (ChromID™ ESBL, Brilliance™ CRE agar, CHROMagar™ KPC). The Carba NP test detected 100% of carbapenemase producers isolated on non-selective media (blood agar, tryticase soy agar, UriSelect™ 4) or on screening media (ChromID™ ESBL, Brilliance™ CRE agar, CHROMagar™ KPC). The Carba NP test gave not interpretable results for 37 % and 29 % of strains recovered from Drigalski and McConkey agar, respectively. Regardless of the manufacturer of Mueller-Hinton agar, 100% of OXA-48, KPC and IMP producers were detected, whereas VIM and NDM producers were detected only from colonies isolated on Mueller-Hinton agar plates from Becton-Dickinson and Oxoid. Zinc supplementation of Mueller-Hinton agar plates restored the ability of the Carba NP test to detect all carbapenemase producers, pointing out the critical role of zinc ion concentration for detecting VIM and NDM-producers. In addition an updated version of the Carba NP test is provided that mostly suppresses the centrifugation steps and allows the detection of carbapenemase producers within 30 min.