Campylobacter aecornae sp. nov., isolated from surface water in Slovenia

During a surveillance study conducted in Slovenia to investigate Campylobacter species from environmental waters, various Campylobacter coli isolates from clades 1 to 3 were isolated. Additionally, a Campylobacter isolate designated CCS1377, originating from the Classical Karst region near Illyrian Bistrica, was initially identified as a relative of C. coli through preliminary identification using multiplex PCR and MALDI-TOF MS. However, these methods did not allow a definite classification of the isolate. In-depth phenotypic analysis revealed characteristics of CCS1377 that were distinct from C. coli and Campylobacter jejuni type strains. This included a unique cell and colony morphology, non-motility, weak autoagglutination and an inability to assimilate succinate. MALDI-TOF MS analysis revealed distinct biomarker ions compared to C. coli RM2228, supporting the hypothesis that CCS1377 represents a novel species. Whole-genome sequencing and comparative genomics confirmed its distinct phylogenetic position. The chromosome of Campylobacter sp. CCS1377 was estimated to be 1,853,379 bp in size with a G+C content of 30.78 mol%, and the genome was predicted to contain 1,878 genes. Average nucleotide identity analysis against genomes available in the NCBI database yielded a maximum value of 81.2% when compared to C. coli type strain NCTC11366^T, significantly below the established species threshold of 94.2%. The digital DNA-DNA hybridization (dDDH) value was also below the species threshold of 70%, with dDDH d₄=22.0% [19.7-24.4%] in comparison to the C. coli type strain NCTC11366^T. Based on these phenotypic and genomic characteristics, we propose the name Campylobacter aecornae sp. nov. for the newly recognized Campylobacter species. The proposed type strain is CCS1377^T (=DSM 102056^T=LMG 33651^T).