Antimicrobial and multidrug-resistant bacteria are a major problem worldwide and, consequently, the surveillance of antibiotic-resistant bacteria and assessment of the dissemination routes are essential. We hypothesized that migratory birds, coming from various environments, would carry more numerous Vibrio strains than sedentary species, with increased risk to be passed to their contacts or environment in habitats they transit or nest in. Similarly, we presumed that strains from migratory birds will show multidrug resistance. A total of 170 oral and rectal swabs were collected from wild birds captured in different locations of the Danube Delta (Malic, Sfantu-Gheorghe, Letea Forest) and processed using standardized selective media. V. cholerae strains were confirmed by serology and molecular methods and, subsequently, their susceptibility was evaluated. The prevalence of Vibrio species by host species, habitat type, and location was interpreted. The isolated Vibrio species were identified as Vibrio cholerae 14.33%, V. fluvialis 13.33%, V. alginolyticus 12%, V. mimicus 17.33%, V. vulnificus 10.88%, with V. parahaemolyticus and V. metschnikovii (16%) also being prevalent. Of the 76 Vibrio spp. isolates, 18.42% were resistant towards at least three antimicrobials, and 81.57% demonstrated a multidrug resistance phenotype, including mainly penicillins, aminoglycosides, and macrolides. The results of the present study indicate higher numbers of Vibrio strains in migratory (74.66%) than in sedentary birds (25.33%), confirming our hypothesis. Furthermore, the increased pathogenicity of Vibrio spp. strains, isolated from wild migratory and sedentary birds, was confirmed by their increased multiple antibiotic resistance (MAR) index (0.09–0.81).

Microbiological risk assessment is vital for identifying and mitigating health hazards associated with microbial contaminants in water and food. This study conducts a comprehensive microbiological risk assessment in Sfântu Gheorghe town, focusing on water and fish-based food sources. The assessment involves the identification and characterization of microbial hazards pose by Vibrio spp. and E. coli contamination, exploring the dose-response relationship, and dynamic evaluations of exposure pathways. In assessing water-related risks, ten strategic sampling points were selected seasonally over eight seasons. Pathogenic occurrences were quantified, and microbial species were evaluated based on survival duration, multiplication potential, and susceptibility to regional meteorological phenomena. Fish-related risks were analysed from capture to primary preparation, addressing contact with untreated water and fish-based food consumption. Qualitative assessments of zoonotic risk, infectivity, and potential to cause foodborne intoxications comprise into a risk score classification. Spatial interpolation methods delineate areas of interest based on frequent contamination observations. The study highlights the necessity for comprehensive studies integrating static and dynamic methodologies to comprehend potential health threats associated with water and fish-based food consumption. The findings underscore the importance of informed policies and interventions for safeguarding public health in the Danube Delta region.