Identification to the Genus Level and Characterisation of Raw Salmon Sushi Bacteria Isolates from Helicobacter pylori Selective Medium

Abstract

Introduction: It is well known that food products might contain environmental microbes that harbour antibiotic resistance genes. These isolates could eventually be deposited into human gut which may cause the possibility of the transfer of resistance genes to the gut flora. In addition, there was a report regarding bacterial infection due to raw fish consumption. These factors led us to characterise the bacteria that were isolated from raw salmon sushi. Methods: In this study, the salmon sushi bacteria were previously isolated from a local restaurant. These showed white colonies formed on the Helicobacter pylori selective medium, which were then processed for 16S rDNA sequencing. All isolates were screened by PCR for the presence of mcr-1, blaKPC-1, blaNDM-1, VanA-C, and mecA genes along with their positive controls. Haemolytic activity was assessed using blood agar, followed by the phenotypic antimicrobial resistance profiling. Results: Out of the 27 isolates, only three isolates were identified as Pseudomonas spp.. The most common isolates of raw salmon sushi that were able to grow on the H. pylori selective medium were Acinetobacter (63%, 17/27) and Weissella (19%, 5/27) species. Most of the isolates did not exhibit their β-haemolytic activity and were susceptible to imipenem and meropenem. Weissella spp. was found resistant to vancomycin and oxacillin only. However, there was a pseudomonad isolate that carried two of the antibiotic resistant genes (blaNDM-1 and VanB). Conclusion:This study outlined that interpretation of the results must be done with caution from the selective medium and detection of antibiotic resistant genes is a must for raw salmon sushi, as some isolates would harbour those genes even they might show susceptible phenotype. Keywords: Helicobacter pylori selective medium, Acinetobacter species, Weissella species, blaNDM-1, VanB