Molecular Identification of Bacteria Isolated from Marketed Sparus aurata and Penaeus indicus Sea Products: Antibiotic Resistance Profiling and Evaluation of Biofilm Formation.

Background: Marketed fish and shellfish are a source of multidrug-resistant and biofilm-forming foodborne pathogenic microorganisms.
Methods: Bacteria isolated from Sparus aurata and Penaeus indicus collected from a local market in Hail region (Saudi Arabia) were isolated on selective and chromogenic media and identified by using 16S RNA sequencing technique. The exoenzyme production and the antibiotic susceptibility patterns of all identified bacteria were also tested. All identified bacteria were tested for their ability to form biofilm by using both qualitative and quantitative assays.
Results: Using 16S RNA sequencing method, eight genera were identified dominated by Vibrio (42.85%), Aeromonas (23.80%), and Photobacterium (9.52%). The dominant species were V. natrigens (23.8%) and A. veronii (23.80%). All the identified strains were able to produce several exoenzymes (amylases, gelatinase, haemolysins, lecithinase, DNase, lipase, and caseinase). All tested bacteria were multidrug-resistant with a high value of the multiple antibiotic index (MARI). The antibiotic resistance index (ARI) was about 0.542 for Vibrio spp. and 0.553 for Aeromonas spp. On Congo red agar, six morphotypes were obtained, and 33.33% were slime-positive bacteria. Almost all tested microorganisms were able to form a biofilm on glass tube. Using the crystal violet technique, the tested bacteria were able to form a biofilm on glass, plastic, and polystyrene abiotic surfaces with different magnitude.
Conclusions: Our findings suggest that marketed S. aurata and P. indicus harbor various bacteria with human interest that are able to produce several related-virulence factors.