Journal Article

Ambler class C-type β-lactamases and porin alterations in Enterobacter cloacae complex and Klebsiella aerogenes in the Netherlands, 2012–2023

Witteveen, Sandra, Notermans, Daan W., Bos, Jeroen, Lansu, Simon, de Haan, Angela, van Meer, Maurits P. A., Hendrickx, Antoni P. A., van der Zwet, Wil, van Gorp, Elke, Ouw, Maureen, Wielders, Cornelia C. H., Wunderink, Herman F., Godeke, Gert-Jan, Landman, Fabian

2026

Overview

We investigated the genomic epidemiology of Ambler class C (AmpC-type) β-lactamases in Enterobacter cloacae complex and Klebsiella aerogenes in the national carbapenemase-producing Enterobacterales (CPE) surveillance of the Netherlands between 2012 and 2023. A total of 399 E. cloacae complex and K. aerogenes isolates from 399 patients were analyzed using whole-genome sequencing to assess genetic relatedness, resistance genes, porin, and AmpC-regulatory gene profiles, plasmid replicons, and the genomic location of AmpC-genes, respectively. Of the 399 patients, 217 were male (54%), and the median age was 67 years. Carbapenemase production was assessed using the carbapenem inactivation method (CIM) and CarbaNP-test. A considerable proportion of E. cloacae complex (32%) and K. aerogenes (52%) isolates were CIM-positive in the absence of detectable carbapenemase genes (IMP, KPC, NDM, OXA-48-like, VIM) by the CarbaPCR, a phenotype termed CIM + Carba-. These isolates were mostly (81.9%) susceptible (EUCAST ≤ 2mg/L) to meropenem. The majority of CIM + Carba + isolates with major carbapenemase genes were gained from pre-emptive screening, while CIM + Carba- isolates were mainly taken for diagnostic purposes. Genomic analysis identified 18 genogroups, with E. kobei , E. roggenkampii , E. ludwigii, and K. aerogenes showing the CIM + Carba- phenotype, were mostly lacking porins and AmpC regulators, and correlated with chromosome-encoded AmpC-type β-lactamases like bla ACT-28 , bla ACT-52, bla MIR-3 , bla MIR-11 or ampC of which the majority (63%) yielded a positive CarbaNP-test. These CIM + Carba- isolates carried only few plasmids, and there was limited evidence of nosocomial spread. CIM + Carba- E. kobei carrying bla ACT-28 overproduced ACT-28 protein in the CIM. Overall, the Enterobacter and K. aerogenes population in the Netherlands is genetically diverse, with most isolates carrying species-specific AmpC-type β-lactamases. Isolates with low MIC for meropenem that lack porins and major carbapenemases represent a low-risk for public health.

• Publisher: BioMed Central,BioMed Central Ltd,Springer Nature B.V,BMC
• Subject: ACT / Aerogenes / AmpC / Analysis / Anopheles / Anti-Bacterial Agents - pharmacology / Antibiotics / Antimicrobial agents / Bacterial Proteins - genetics / Bacterial Proteins - metabolism / Beta lactamases / beta-Lactamases - genetics / beta-Lactamases - metabolism / Biological Microscopy / Biomedical and Life Sciences / Carbapenemase / Carbapenems / Control / DNA sequencing / Drug resistance / Enterobacter / Enterobacter aerogenes - drug effects / Enterobacter aerogenes - enzymology / Enterobacter aerogenes - genetics / Enterobacter aerogenes - isolation & purification / Enterobacter cloacae / Enterobacter cloacae - drug effects / Enterobacter cloacae - enzymology / Enterobacter cloacae - genetics / Enterobacter cloacae - isolation & purification / Enterobacteriaceae Infections - epidemiology / Enterobacteriaceae Infections - microbiology / Enzymes / Epidemiology / Gene sequencing / Genes / Genetic aspects / Genomes / Genomic analysis / Genomics / Humans / Identification and classification / Imipenem / K. aerogenes / Klebsiella / Klebsiella aerogenes / Klebsiella Infections - epidemiology / Klebsiella Infections - microbiology / Laboratories / Life Sciences / Meropenem / Microbial Sensitivity Tests / Microbiology / Mycology / Netherlands - epidemiology / Nosocomial infections / Nucleotide sequencing / Oxalic acid / Parasitology / Pathogens / Phenotypes / Plasmids / Plasmids - genetics / Porins / Porins - genetics / Porins - metabolism / Public health / Questionnaires / Surveillance / Time trends (Statistics) / Virology / Whole Genome Sequencing / β Lactamase