Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten)

Our data might help to predict the risk of treatment failure with oxyimino-cephalosporins in infections by different Enterobacterales with inducible AmpC. Moreover, we make a proposal for optimization of the current EUCAST expert rule.

ampC derepression cefepime Citrobacter freundii complex Enterobacter cloacae complex Hafnia alvei Klebsiella aerogenes Morganella morganii Providencia spp. Serratia spp. a b s t r a c t Objectives: We aimed to evaluate the effect of ampC derepression on the cefepime MIC in different species of Enterobacterales with chromosomally encoded inducible AmpC b-lactamase.Methods: We analysed a large number of wild-type/mutant pairs (n ¼ 1030 in total). Cefepime MICs were determined by broth microdilution according to EUCAST recommendations. Results: ampC derepression led to increases in MIC by up to 10 dilutions, and significant increases by > 2 MIC dilutions were common across species (744/1030 mutants (72.2%) in total). Interestingly, the frequency of cefepime S/I/S/R transitions varied considerably between species: 66.3% in Enterobacter cloacae complex (167/252 mutants), 1.1% in Klebsiella aerogenes (2/180 mutants), 18.1% in Citrobacter freundii complex (50/277 mutants), 36.4% in Hafnia alvei (59/162 mutants), 19.0% in Providencia rettgeri (4/21 mutants), 22.9% in Providencia stuartii (11/48 mutants), 12.3% in Serratia marcescens (7/57 mutants), 20.0% in Serratia liquefaciens (6/30 mutants) and 0% in Morganella morganii (0/3 mutants).