Prevalence, typing and antimicrobial resistance of Salmonella isolates from commercial shellfish in the North coast of Morocco

Antibiotic resistance, virulence and genetic characteristics of Vibrio alginolyticus isolates from aquatic environment in costal mariculture areas in China

Vibrio alginolyticus has been the second most common Vibrio species in the world and mainly grows in the ocean or estuary environment, which can induce epidemics outbreaks under marine organisms, and causing serious economic losses in aquaculture industry. In this study, the genetic populations and evolutionary relationship analysis of V. alginolyticus isolated from different geographical locations in China with typical interannual differences were exhibited originally genetic diversity. Then the virulence genes prevalence, antibiotic resistance phenotype, and antimicrobial resistance genes risk diversity of V. alginolyticus were analyzed by phenotypic and molecular typing methods. And they were complex correlations among antibiotic phenotypes, resistance and virulence genes under different genotype of V. alginolyticus. The results provide a theoretical foundation for further understanding the genetic and metabolic diversity among V. alginolyticus in China, and lay a theoretical foundation for the transmission risk assessment and regional diagnosis of Vibrio in aquatic animals.

Integration assay of bacteriological risks in marine environment using salmonella spp and multimarker response in the bivalve Donax trunculus: Novel biomonitoring approach

Microbiological contamination is one of the riskiest forms of human contamination in seawater, which threaten the stability of ecosystems and human health. In this study, we study the accumulation of a pathogenic bacteria Salmonella spp; isolated from the marine environment, in the soft tissue of Donax trunculus (Mollusca, Bivalvia), a commonly used as a bioindicators species for aquatic ecosystems monitoring, under laboratory conditions during both exposure and recovery periods. These bacteria were added in seawater at three concentrations previously determined against sentinel specie at three exposure periods (24, 48 and 96 h). In a second series of experiments, exposed specimens were afterward transplanted to clean water to assess the recovery pattern. The mortality rate of bivalves was determined as biomarker of general stress. Our findings suggest that microbiological contamination by Salmonella spp was gradually incorporated into the body of D. trunculus causing a significant induction of enzymatic activity of acetylcholinesterase (AChE), Catalase (CAT), glutathione-S-transferase (GST) and malondialdehyde (MDA) levels, as a function of time and concentration. Exposure to a bacterial concentration of 5.10⁴ bacteria/liter resulted in the mortality of more than 80% of the specimens. This study is to test the pathogenicity of Salmonella strains at concentrations close to those of the marine environment, and their effects on biomarkers, thus deducing the existence of an exponential relationship between bacterial concentrations and enzymatic response. The principal component analysis shows that the four biomarkers had similar variation with bacterial concentrations, while two groups were obtained to change following the exposure time (CAT-GST and AChE-MDA). This study provides new findings on the potential accumulation of pathogenic bacteria associated with neurotoxicity and oxidative stress in the wedge clam Donax trunculus.

An Evaluation of the Pathogenic Potential, and the Antimicrobial Resistance, of Salmonella Strains Isolated from Mussels

Salmonella spp. and antimicrobial resistant microorganisms are two of the most important health issues worldwide. In the present study, strains naturally isolated from mussels harvested in Galicia (one of the main production areas in the world), were genetically characterized attending to the presence of virulence and antimicrobial resistance genes. Additionally, the antimicrobial profile was also determined phenotypically. Strains presenting several virulence genes were isolated but lacked all the antimicrobial resistance genes analyzed. The fact that some of these strains presented multidrug resistance, highlighted the possibility of bearing different genes than those analyzed, or resistance based on completely different mechanisms. The current study highlights the importance of constant surveillance in order to improve the safety of foods.