Full genome of Paenimyroides ceti strain MC-ZM-24 producing a new subclass B1 metallo-β-lactamase.

Objectives Paenimyroides ceti is a newly defined species belonging to the Flavobacteriaceae family. It was originally isolated from the lung and liver of two beaked whales. Here, we report the first complete circular genome of a P. ceti and provide insights into its antimicrobial resistance determinants. Methods P. ceti strain MC-ZM-24 was isolated from homogenized tissues of Zophobas morio larvae. Antimicrobial susceptibility tests were determined by broth microdilution and carbapenemase production was assesed by Blue-Carba test. Whole-genome sequencing (WGS) was obtained using both the Illumina short-read and Oxford Nanopore long-read technologies. A hybrid genome assembly was generated with Unicycler and subsequently annotated using the NCBI Prokaryotic Genome Annotation Pipeline. Antimicrobial resistance genes were identified using AMRFinder and ResFinder. Known metallo-β-lactamase (MBL) protein sequences deposited in NCBI GenBank and UniProt databases were compared with that of strain MC-ZM-24. Results The genome comprised a single circular chromosome of 3,274,043-bp, with 3,053 genes, and exhibited a GC content of 35.56%. Phenotypically, the strain was multidrug-resistant, non-susceptible to carbapenems and produced a carbapenemase. WGS analysis identified a unique chromosomal bla gene encoding a MBL that harbors the conserved subclass B1 motifs, but shares low sequence identity with previously described MBL enzymes. Conclusions The complete genome of P. ceti MC-ZM-24 expands our understanding of Paenimyroides ecology and evolution. It also highlights an intrinsic subclass B1 β-lactamase, extending the repertoire of chromosomal MBLs in Flavobacteriaceae. This new MBL will require further detailed characterization.