The Use of Two Culturing Methods in Parallel Reveals a High Prevalence and Diversity ofArcobacterspp. in a Wastewater Treatment Plant

The genusArcobacterincludes species considered emerging food and waterborne pathogens. DespiteArcobacterhas been linked to the presence of faecal pollution, few studies have investigated its prevalence in wastewater, and the only isolated species wereArcobacter butzleriandArcobacter cryaerophilus. This study aimed to establish the prevalence ofArcobacterspp. at a WWTP using in parallel two culturing methods (direct plating and culturing after enrichment) and a direct detection by m-PCR. In addition, the genetic diversity of the isolates was established using the ERIC-PCR genotyping method. Most of the wastewater samples (96.7%) were positive forArcobacterand a high genetic diversity was observed among the 651 investigated isolates that belonged to 424 different ERIC genotypes. However, only few strains persisted at different dates or sampling points. The use of direct plating in parallel with culturing after enrichment allowed recovering the species A.butzleri, A.cryaerophilus,Arcobacter thereius,Arcobacter defluvii,Arcobacter skirrowii,Arcobacter ellisii,Arcobacter cloacae, andArcobacter nitrofigilis, most of them isolated for the first time from wastewater. The predominant species was A.butzleri, however, by direct plating predominated A.cryaerophilus. Therefore, the overall predominance of A.butzleriwas a bias associated with the use of enrichment.