A rapid and inexpensive protocol to screen for third generation cephalosporin-resistant and non-fermenting Gram-negative rods directly in positive blood cultures.

Third generation cephalosporins are frequently used in the first-line treatment of Gram-negative rod (GNR) bacteremia but are unsuitable in the case of extended-spectrum-beta-lactamase-producing Enterobacterales (ESBL-E) or non-fermenting GNR infections. The aim of this study was to develop and evaluate a simple and rapid two-test protocol involving oxidase and β-Lacta tests performed directly on positive blood culture broth as a preliminary screen for non-fermenting or third generation cephalosporins-resistant GNR. The diagnostic performance of this approach was evaluated on 294 bottles for the oxidase test and 267 bottles for the β-Lacta Test.