Fish bacterial flora identification via rapid cellular fatty acid analysis

Abstract

Seafood quality can be assessed by determining the bacterial load and flora composition, although classical taxonomic methods are time-consuming and subjective to interpretation bias. A two-prong approach was used to assess a commercially available microbial identification system: confirmation of known cultures and fish spoilage experiments to isolate unknowns for identification. Bacterial isolates from the Fishery Industrial Technology Center Culture Collection (FITCCC) and the American Type Culture Collection (ATCC) were used to test the identification ability of the Sherlock Microbial Identification System (MIS). Twelve ATCC and 21 FITCCC strains were identified to species with the exception of Pseudomonas fluorescens and P. putida which could not be distinguished by cellular fatty acid analysis. The bacterial flora changes that occurred in iced Alaska pink salmon (Oncorhynchus gorbuscha) were determined by the rapid method. Fresh fish contained up to 7 genera in which the aerobic plate counts (APC) was 3.04 log colony-forming units (CFU)/cm². As the fish spoiled, the APC increased to 6.60 log CFU/cm² and the flora was composed of P.fluorescens/putida, Psychrobacter immobilis and Shewanella putrefaciens. The Sherlock MIS rapidly and accurately identified seafood bacteria in fresh fish and can be used to monitor quality changes during iced storage of fish.