Enterotoxin genes and antimicrobial resistance in Staphylococcus aureus isolated from food products in Algeria.

AIMS: The aim of this study was to characterize Staphylococcusaureus isolates of food origin (dairy and meat products, pastries and sandwiches) determining the carriage in enterotoxin genes and the antimicrobial resistance pheno/genotypes. METHODS AND RESULTS: A total of 300 food samples were collected and analysed for the detection of S. aureus. The presence of enterotoxin genes was investigated by multiplex PCRs. Resistance of isolates to 11 antimicrobials was determined using disc diffusion method and molecular characterization of methicillin-resistant S. aureus was carried out by spa typing and multilocus sequence typing. Overall, 51 out of 300 samples (17%) were contaminated with S. aureus, and 104 isolates were recovered. In all, 65 of these isolates (62·5%) harboured one or more genes encoding for staphylococcal enterotoxins, being seg and sei the most observed genes. The highest resistance profile was ascribed to penicillin G (95·19%). Five isolates were methicillin-resistant (MRSA) harbouring the mecA gene. All MRSA isolates belonged to the sequence type ST5 and to two different spa types (t450 and t688); the MRSA-t450 isolate carried the scn gene (specific marker of the immune evasion cluster system), but the four MRSA-t688 isolates were scn negative. The MRSA isolates carried enterotoxin genes but were negative for the genes of the Panton Valentine leukocidine (lukF/S-PV). CONCLUSION: The presence of enterotoxigenic S. aureus isolates, including MRSA, in food samples can represent a risk for public health. SIGNIFICANCE AND IMPACT OF THIS STUDY: This work describes the molecular characteristics of MRSA strains isolated from foods in Algeria and it can contribute to an extended database concerning the S. aureus isolated from food origin.

Production of clovamide and its analogues in Saccharomyces cerevisiae and Lactococcus lactis.

Clovamide and its analogues are N-hydroxycinnamoyl-L-amino acids (HAA) that exhibit antioxidant activities. For environmental and economic reasons, biological synthesis of these plant-derived metabolites has garnered interest. In this study, we exploited HDT1, a BAHD acyltransferase recently isolated from red clover, for the production of clovamide and derivatives in S. cerevisiae and L. lactis. HDT1 catalyses the transfer of hydroxycinnamoyl-coenzyme A (CoA) onto aromatic amino acids. Therefore, by heterologously co-expressing HDT1 with 4-coumarate:CoA ligase (4CL), we succeeded in the biological production of clovamide and more than 20 other HAA, including halogenated ones, upon feeding the engineered micro-organisms with various combinations of cinnamates and amino acids. To the best of our knowledge, this is the first report on the biological synthesis of HAA and, more generally, on the synthesis of plant-derived antioxidant phenolic compounds in L. lactis. The production of these health beneficial metabolites in Generally Recognized As Safe (GRAS) micro-organisms such as S. cerevisiae and L. lactis provides new options for their delivery as therapeutics. SIGNIFICANCE AND IMPACT OF THE STUDY: N-hydroxycinnamoyl-L-amino acids such as clovamide are bioactive plant-derived phenolic compounds with health beneficial effects. Relying on chemical synthesis or direct extraction from plant sources for the supply of these valuable molecules poses challenges to environmental sustainability. As an alternative route, this work demonstrates the potential for biological synthesis of N-hydroxycinnamoyl-L-amino acids using engineered microbial hosts such as Saccharomyces cerevisiae and Lactococcus lactis. Besides being more eco-friendly, this approach should also provide more structurally diverse compounds and offer new methods for their delivery to the human body.