Prevalence and Distribution of Potentially Human Pathogenic Vibrio spp. on German North and Baltic Sea Coasts

Abstract

Global ocean warming results in an increase of infectious diseases including an elevated emergence of <i>Vibrio</i> spp. in Northern Europe. The European Centre for Disease Prevention and Control reported annual periods of high to very high risks of infection with <i>Vibrio</i> spp. during summer months along the North Sea and Baltic Sea coasts. Based on those facts, the risk of <i>Vibrio</i> infections associated with recreational bathing in European coastal waters increases. To obtain an overview of the seasonal and spatial distribution of potentially human pathogenic <i>Vibrio</i> spp. at German coasts, this study monitored <i>V. cholerae</i>, <i>V. parahaemolyticus</i>, and <i>V. vulnificus</i> at seven recreational bathing areas from 2017 to 2018, including the heat wave event in summer 2018. The study shows that all three <i>Vibrio</i> species occurred in water and sediment samples at all sampling sites. Temperature was shown to be the main driving factor of <i>Vibrio</i> abundance, whereas <i>Vibrio</i> community composition was mainly modulated by salinity. A species-specific rapid increase was observed at water temperatures above 10°C, reaching the highest detection numbers during the heat wave event with abundances of 4.5 log10 CFU+1/100 ml of seawater and 6.5 log10 CFU+1/100 g of sediment. Due to salinity, the dominant <i>Vibrio</i> species found in North Sea samples was <i>V. parahaemolyticus</i>, whereas <i>V. vulnificus</i> was predominantly detected in Baltic Sea samples. Most detections of <i>V. cholerae</i> were associated with estuarine samples from both seas. <i>Vibrio</i> spp. concentrations in sediments were up to three log higher compared to water samples, indicating that sediments are an important habitat for <i>Vibrio</i> spp. to persist in the environment. Antibiotic resistances were found against beta-lactam antibiotics (ampicillin 31%, cefazolin 36%, and oxacillin and penicillin 100%) and trimethoprim-sulfamethoxazole (45%). Moreover, isolates harboring pathogenicity-associated genes such as <i>trh</i> for <i>V. parahaemolyticus</i> as well as <i>vcg</i>, <i>cap</i>/<i>wcv</i>, and the 16S rRNA-type B variant for <i>V. vulnificus</i> were detected. All sampled <i>V. cholerae</i> isolates were identified as non-toxigenic non-O1/non-O139 serotypes. To sum up, increasing water temperatures at German North Sea and Baltic Sea coasts provoke elevated <i>Vibrio</i> numbers and encourage human recreational water activities, resulting in increased exposure rates. Owing to a moderate Baltic Sea salinity, the risk of <i>V. vulnificus</i> infections is of particular concern.