Identification and serotyping of Listeria monocytogenes, isolated from various salmon products, sold in retail market in Lithuania

Genetic population structure of Listeria monocytogenes strains isolated from salmon and trout sectors in France

Smoked salmon and smoked trout are ready-to-eat and potentially contaminated with the pathogenic bacterium Listeria monocytogenes making them high risk for the consumer. This raises questions about the presence of hypervirulent or persistent strains in the salmon and trout industries. Knowledge of the genetic diversity of circulating strains in these sectors is essential to evaluate the risk associated with this pathogen and improve food safety. We analyzed the genetic structure of 698 strains of L. monocytogenes isolated from 2006 to 2017 in France, based on their serogroup, lineage and clonal complexes (CCs) determined by Multilocus sequence typing (MLST). Most of the CCs were identified by mapping the strains PFGE profiles and a novel high-throughput real-time PCR method for CC identification. We identified thirteen CCs and one sequence type (ST) with variable distribution in salmon and trout samples (food, environment). The three most prevalent CCs were CC121, CC26 and CC204. Strains from ST191 and CC54 were detected for the first time in these sectors, while less than 0.6% of the isolates belonged to the hyper-virulent CC1, CC6 and CC20. No CC was exclusively associated with the salmon sector. This project allowed us to assess the population diversity of CCs of L. monocytogenes in the salmon and trout industries.

Antimicrobial of tropical fruit and vegetable waste extract for food-borne pathogenic bacteria

Tropical fruit and vegetable wastes become great potential natural resources of bioactive compounds for antimicrobial. The aim of the study was to determine the effect of antimicrobial extracted from tropical fruit and vegetable waste to inhibit foodborne pathogenic bacteria (Aeromonas hydrophilla, Bacillus cereus, Escherichia coli, Listeria monocytogenes, Salmonella Typhimurium, Staphylococcus aureus, Vibrio parahaemolyticus). A total of six tropical fruit waste (peel of pineapple, jackfruit, durian, coffee, mangosteen, and cacao pods) and five tropical vegetable waste (stem of sembukan, lamtoro pods, jengkol shell, bitter bean pods, Indian marsh fleabane leave) was extracted by using maceration method. The antimicrobial activity of extracts was carried out by using disc diffusion assay and Minimum Inhibitory Concentration. The flavonoids in extract were identified and quantified by using Liquid Chromatography-Mass Spectrometry. The highest antimicrobial activity against Gram-positive bacteria (B. cereus, L. monocytogenes and S. aureus) was shown by jengkol, bitter bean and mangosteen waste extract in the range of 0,00038 to 4,2% for MIC. The highest antimicrobial activity inhibits Gram-negative bacteria (A. hydrophilla, E. coli, S. Typhimurium and V. parahaemolyticus) was shown by jengkol, bitter bean, mangosteen, sembukan and lamtoro waste extract in the range of 0,00038 to 3,1% for MIC which have apigenin, catechin, coumaric acid, gallic acid, genistein, hydroxybenzoic acids, luteolin, myricetin, naringenin dan quercetin as bioactive compounds. Total phenol of those waste extracts was in the range of 0.663 to 4,441 mg GAE/g. Jengkol, bitter bean, mangosteen, sembukan and lamtoro waste extract shown to be a potential natural antimicrobial to inhibit food-borne pathogenic bacteria.