Combined TCBS and CHROMagar analyses allow basic identification of Vibrio vulnificus within a 48h incubation period in the coastal Baltic Sea

With rising infection rates in recent years Vibrio vulnificus pose an increasing threat to public safety in the coastal brackish Baltic Sea. It is therefore important to be able to monitor this organism and assess its risk potential for the society on a more regular basis. However, as the coastline of the Baltic Sea is 8,000 km long and shared by nine nations, a convenient, fast, inexpensive, yet efficient V. vulnificus identification method is essential. We evaluated the effectiveness of a two-step agar-based approach for V. vulnificus in comparison with V. cholerae, V. parahaemolyticus, and V. alginolyticus consisting of successive Vibrio isolation and cultivation on thiosulphate-citrate-bile salt sucrose (TCBS) and CHROMagar, respectively. Our study contains isolates from water and sediment across a broad expanse of the Baltic Sea including 13 locations and 2 different summers, the time of year during which Vibrio infections are usually much more frequent. Confirmation of isolate species was carried out using molecular analyses. The two-step agar plating method performed well across different locations and timeframes in identifying V. vulnificus by more than 80%, but sensitivity in other Vibrio species varied. Thus, our approach yielded promising results as a potential tool for early V. vulnificus detection across a broad timeframe and transect of the Baltic Sea and potentially other brackish environments.