Tracking antimicrobial resistance indicator genes in wild flatfish from the English Channel and the North Sea area: A one health concern

Global quantification and distribution of antibiotic resistance genes in oceans and seas: Anthropogenic impacts and regional variability

The global spread of antibiotic resistance genes (ARGs) in the marine environment poses a significant threat to public health and natural ecosystems. This study quantified and analysed the distribution and co-occurrence patterns of ARGs in a wide range of oceans and high seas, including the Atlantic, Arctic and Indian Ocean, the Mediterranean Sea and the Persian Gulf. Focusing on beta-lactamases (blaOXA-48, blaCTX-M-1 group, and blaTEM), sulfonamides (sul1) and tetracycline (tetA), our results showed that sul1 was ubiquitous, indicating widespread dissemination. Notably, the Mediterranean Sea exhibited higher levels of multiple ARGs in single samples, suggesting significant anthropogenic impact. Interestingly, the Arctic Ocean, particularly around the Svalbard Islands, also showed the presence of multiple ARGs, highlighting the pervasive occurrence of antibiotic resistance in remote areas. We employed two clustering approaches to explore ARG patterns, primarily focusing on identifying geographic trends and differences in ARG abundance. Additionally, we investigated potential sources of contamination, including proximity to wastewater treatment plants, ports, marine traffic, and currents. These findings clearly demonstrate that antibiotic resistance gene contamination is widespread across diverse marine environments, with significant regional variations. This underscores the urgent need for tailored intervention strategies and global collaboration to mitigate the spread of ARGs and manage their complex dynamics in marine ecosystems.

Occurrence of Antimicrobial-Resistant Bacteria in Intestinal Contents of Wild Marine Fish in Chile

Antimicrobial-resistant bacteria (ARB) from the intestinal contents of wild fish may have a relevant ecological significance and could be used as indicators of antimicrobial-resistance dissemination in natural bacterial populations in water bodies impacted by urban contamination. Thus, the occurrence of ARB in the intestinal contents of pelagic and demersal wild fishes captured in anthropogenic-impacted Coquimbo Bay in Chile was studied. Culturable counts of total and antimicrobial-resistant bacteria were determined by a spread plate method using Trypticase soy agar and R2A media, both alone and supplemented with the antimicrobials amoxicillin, streptomycin, florfenicol, oxytetracycline and ciprofloxacin, respectively. Heterotrophic plate counts of pelagic and demersal fishes ranged from 1.72 × 106 CFU g-1 to 3.62 × 109 CFU g-1, showing variable proportions of antimicrobial resistance. Representative antimicrobial-resistant isolates were identified by 16S rRNA gene sequencing, and isolates (74) from pelagic fishes mainly belonged to Pseudomonas (50.0%) and Shewanella (17.6%) genera, whereas isolates (68) from demersal fishes mainly belonged to Vibrio (33.8%) and Pseudomonas (26.5%) genera. Antimicrobial-resistant isolates were tested for susceptibility to 12 antimicrobials by an agar disk diffusion method, showing highest resistance to streptomycin (85.2%) and amoxicillin (64.8%), and lowest resistance to oxytetracycline (23.2%) and ciprofloxacin (0.7%). Only furazolidone and trimethoprim/sulfamethoxazole were statistically different (p < 0.05) in comparisons between isolates from pelagic and demersal wild fishes. Furthermore, an important number of these isolates carried plasmids (53.5%) and produced Extended-Spectrum-β-lactamases (ESBL) (16.9%), whereas the detection of Metallo-β-Lactamases and class 1-integron was rare. This study provides evidence that wild fish are important reservoirs and spreading-vehicles of ARB, carrying plasmids and producing ESBLs in Chilean marine environments.

Monitoring indicator genes to assess antimicrobial resistance contamination in phytoplankton and zooplankton communities from the English Channel and the North Sea

Phytoplankton and zooplankton play a crucial role in marine ecosystems as the basis of the food webs but are also vulnerable to environmental pollutants. Among emerging pollutants, antimicrobial resistance (AMR) is a major public health problem encountered in all environmental compartments. However, the role of planktonic communities in its dissemination within the marine environment remains largely unexplored. In this study, we monitored four genes proposed as AMR indicators (tetA, blaTEM, sul1, and intI1) in phytoplankton and zooplankton samples collected in the English Channel and the North Sea. The indicator gene abundance was mapped to identify the potential sources of contamination. Correlation was assessed with environmental parameters to explore the potential factors influencing the abundance of AMR in the plankton samples. The prevalence in phytoplankton and zooplankton of sul1 and intI1, the most quantified indicator genes, ranged from 63 to 88%. A higher level of phytoplankton and zooplankton carrying these genes was observed near the French and English coasts in areas subjected to anthropogenic discharges from the lands but also far from the coasts. Correlation analysis demonstrated that water temperature, pH, dissolved oxygen and turbidity were correlated to the abundance of indicator genes associated with phytoplankton and zooplankton samples. In conclusion, the sul1 and intI1 genes would be suitable indicators for monitoring AMR contamination of the marine environment, either in phytoplankton and zooplankton communities or in seawater. This study fills a part of the gaps in knowledge about the AMR transport by marine phytoplankton and zooplankton, which may play a role in the transmission of resistance to humans through the marine food webs.