‘Bacteraemia with an MBL-producing Klebsiella pneumoniae: treatment and the potential role of cefiderocol heteroresistance’–authors’ response
Year: 2022
Type: article
Abstract: We appreciate the inquiry from Longshaw et al. with regards to our case report entitled ‘Bacteraemia with an MBL-producing Klebsiella pneumoniae: treatment and the potential role of cefiderocol heteroresistance’.1 We agree, as stated in our original report, that it is unclear whether the patient was re-infected with the same Klebsiella isolate adherent to a retained indwelling catheter or potentially from a lack of complete bacterial killing due to cefiderocol heteroresistance. As Longshaw and colleagues suggest, Ockham’s razor may provide an alternative explanation, but in this complex case Hickham’s dictum may be equally plausible. Thus, we felt it was important to report our experience given the prior concerns regarding the effectiveness of cefiderocol and potential of heteroresistance as a contributor to our patient’s clinical course. We thank Longshaw et al. for catching a critical misstatement in our paper’s supplementary material—iron-limited, cation-adjusted Mueller–Hinton, rather than standard Mueller–Hinton broth, was indeed used to grow the isolates per CLSI methodology and then plated on standard Mueller–Hinton agar for the population analysis profile (PAP).2 Despite iron being present in Mueller–Hinton agar, this iron is not thought to be free and bacteria have previously been shown to have a phenotype consistent with iron limitation on standard agar.3,4 Furthermore, we follow CLSI guidelines for cefiderocol susceptibility testing on solid medium. Importantly, the ‘PAP MIC’ we reported was specifically for the resistant subpopulation of cells, meaning the concentration at which the very minor frequency of resistant cells could survive, rather than an MIC for the strain as a whole.
DOI: 10.1093/jac/dkac330
Institutions: Emory University, Georgia Department of Public Health
Language: English
Subfield: Molecular Medicine
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W4298089010