Weissella confusa with thermostable β-hemolytic exopolysaccharide. (30th October 2021) - Siavoshi, Farideh
Abstract: Consuming cooked meat contaminated with bacteria that carry thermostable hemolytic exopolysaccharide (ESP), could lead to severe diseases. Culture of a 5- h boiled sample of meat goulash on blood agar showed growth of a gram positive rod-shaped, mucoid and hemolytic bacterium. Biochemical tests and amplification of 1500 bp product of 16S rDNA and sequencing revealed bacterial identity as Weissella confusa . After 1 h boiling of bacterial suspension, they were alive and hemolytic, increased in volume and aggregated. After 8 h boiling of bacterial suspension with coverslip, live bacteria showed hemolysis, clustered and adhered to coverslip. Bacterial bacteriocin and hemolytic activities remained unchanged upon autoclaving. Purified bacterial EPS retained hemolytic activity after autoclaving. Boiling contaminated meat had no negative impact on viability of heat-stable W. confusa and its hemolytic EPS. Thermostable hemolytic EPS protected W. confusa from excessive heat. Hygienic practice in butcheries and kitchens are necessary to eliminate bacterial contaminants. Highlights: W. confusa was isolated from a well-heated meat goulash. W. confusa produced thermostable exopolysaccharide (EPS) with hemolytic activity. EPS had a unique microstructure that reduced thermal conductivity. W. confusa had thermostable bacteriocin. W. confusa was resistant to a wide range of antibiotics.