Occurrence and genetic diversity of Arcobacter spp. in a spinach-processing plant and evaluation of two Arcobacter-specific quantitative PCR assays

Some species of the genus Arcobacter are considered to be emerging food pathogens. With respect to recent vegetable-borne outbreaks, the aim of this work was to investigate the occurrence and diversity of Arcobacter within the production chain of a spinach-processing plant by a combination of cultivation and molecular methods. Samples including spinach, water, and surface biofilm were taken over a period of three years from the entire processing line. Ten 16S rRNA (rrs) gene clone libraries were constructed and analysed using amplified rRNA gene restriction analysis (ARDRA). Approximately 1200 clones were studied that resulted in 44 operational taxonomic units (OTUs). Sequences with high similarities to Arcobacter cryaerophilus (13% of clones, 3 OTUs), A. ellisii (4%, 6 OTUs), A. suis (15%, 3 OTUs), and the type strain of A. nitrofigilis (1%, 7 OTUs) were identified. This represents the first report of the detection of the recently described species A. ellisii, A. suis and, in addition, A. venerupis from alternative habitats. A total of 67% of the clones (22 OTUs) could not be assigned to a genus, which indicated the presence of uncharacterised Arcobacter species.