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 NCTC11366T, 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 NCTC11366T. 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 CCS1377T (=DSM 102056T=LMG 33651T).