Prevalence and Antimicrobial Resistance of Enteropathogenic Bacteria in Yellow-Legged Gulls (Larus michahellis) in Southern Italy

SIMPLE SUMMARY: Several Mediterranean countries have suffered from a significant increase in the populations of gulls. These birds are agile fliers and are able to adapt easily to different habitats and to profit from food discarded by humans. In addition, gulls may be considered by some as pests, given their interactions with human activities, and have been described as carriers, but actually function as environmental sentinels of enteropathogenic bacteria and antibiotic-resistant strains. Therefore, the aim of this study was to examine the role of gulls as vectors of zoonotic agents of high importance for human health and as potential reservoirs of antimicrobial-resistant strains. ABSTRACT: Wild birds may host and spread pathogens, integrating the epidemiology of infectious diseases. Particularly, Larus spp. have been described as responsible for the spread of many enteric diseases, primarily because of their large populations at landfill sites. The aim of this study was to examine the role of yellow-legged gulls as a source of enteropathogenic bacteria such as Campylobacter spp., Salmonella spp., Shiga toxin-producing Escherichia coli and Yersinia spp., with particular attention to antibiotic-resistant strains. Enteropathogenic bacteria were isolated from 93/225 yellow-legged gulls examined from April to July, during a four-year period (2016–2019). Specifically, Campylobacter spp. was isolated from 60/225 samples (26.7%), and identified as C. coli (36/60) and as C. jejuni (24/60). Salmonella spp. was isolated from 3/225 samples (1.3%), and identified as Salmonella arizonae. Shiga toxin-producing E. coli were isolated from 30/225 samples (13.3%) samples, and serotyped as E. coli O128 (12/30) O26 (9/30), O157 (6/30) and O11 (3/30); Yersinia spp. was never detected. Isolated strains exhibited multidrug resistance, including vitally important antibiotics for human medicine (i.e., fluoroquinolones, tetracyclines). Our study emphasizes the importance of yellow-legged gulls as potential reservoirs of pathogenic and resistant strains and their involvement in the dissemination of these bacteria across different environments, with resulting public health concerns.