Flores protectrices pour la conservation des aliments

Synthèse bibliographique consacrée à l’évaluation de flores protectrices pour améliorer la qualité microbiologique des aliments, cet ouvrage recense les espèces bactériennes et les mécanismes mis en jeu pour lutter contre les flores indésirables, principalement pathogènes. Les critères requis pour la sélection de flores protectrices efficaces ainsi que des exemples dans les principales filières alimentaires sont présentés

Tetracycline Gene Transfer in Staphylococcus xylosus in situ During Sausage Fermentation

International audienceThe presence of determinants of resistance to antibiotics can constitute a possible safety hazard in coagulase-negative staphylococci (CNS), which are widely present in food of animal origin. Among CNS, S. xylosus is a species frequently isolated from fermented meat products. Resistance to tetracycline was found to be one of the most distributed resistances occurring in S. xylosus strains isolated from fermented sausages. We evaluated the transfer of tetracycline resistance in vitro and in situ between S. xylosus strains. We selected three strains isolated from dry fermented sausages, resistant to tetracycline but not to minocycline, their resistance occurring by a mechanism of active efflux encoded by the tetK gene. Only one strain was able to transfer its tetracycline resistance to a recipient strain initially susceptible and plasmid-free using a filter mating procedure. Transfer of tetracycline resistance was observed at very low frequencies of 3.4 × 10-9 per recipient. To further investigate the transferability of this tetracycline resistance, the donor and recipient strains were tested in pilot-scale fermented sausage production. This transfer was possible but at a low rate, 1.4 × 10-7, and only under conditions of a high inoculation level of 108 CFU/g of meat. The tetK gene is located on a small mobilizable plasmid close to Staphylococcus aureus pT181 plasmid. In conclusion, the transfer of tetracycline resistance between strains of S. xylosus is possible, but at a really low frequency in vitro and in situ in fermented sausages. Even if this represents a very moderate risk, it should be taken into account as required by the European approach of Qualified Presumption of Safety (QPS) and AFSSA safety recommendations, advising that strains used as starter cultures should not carry any transferable antibiotic resistance

Vers une règlementation appropriée des flores protectrices

National audienc

Introduction - La biopréservation et les microorganismes bioprotecteurs

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Impact of reducing nitrate/nitrite levels on the behavior of Salmonella Typhimurium and Listeria monocytogenes in French dry fermented sausages

International audienc

La connaissance approfondie des communautés bactériennes des aliments et ses conséquences pour l’utilisation de la biopréservation

National audienc

Development of Lactobacillus sakei strain cocktails to improve hygienic quality of raw beef meat products

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Development of Lactobacillus sakei strain cocktails to improve hygienic quality of raw beef meat products

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Intra-species diversity of Lactobacillus sakei as a tool for designing biopreservative cultures of fresh meat

absen

Biodiversity of coagulase-negative Staphylococci in French cheeses, dry fermented sausages, processing environments and clinical samples.

International audienceIn this study, the biodiversity of Coagulase-Negative Staphylococci (CNS) strains isolated in France from cheese related samples (227 isolates) and dry sausage related samples (204 isolates) was compared to the biodiversity of 297 clinical isolates. Species identification was performed using different molecular methods (specific PCR, "Staph array" hybridization and sodA gene sequencing). Infraspecific biodiversity of strains belonging to the main CNS species found in both food and clinical samples was then assessed by pulse-field gel electrophoresis (PFGE). For food-related samples, the main species encountered corresponded to Staphylococcus equorum (28.5%), S. xylosus (28.3%), S. saprophyticus (12.5%) and S. succinus (7.7%); while, for clinical isolates, the main species encountered corresponded to S. epidermidis (69.4%), S. capitis (9.8%), S. hominis (4.5%), S. warneri (4.5%) and S. haemolyticus (3.8%). The two main species common to both food and clinical samples corresponded to S. epidermidis and S. saprophyticus. Concerning infraspecific biodiversity, PFGE profiles of S. equorum, S. saprophyticus and S. epidermidis showed a large genomic biodiversity. Comparatively, S. xylosus exhibited a lower biodiversity. No correlation could be observed between PFGE patterns and either the geographical origin or the sample type. This study highlighted that no food strains had similar PFGE profiles to clinical ones and that the two main food-related species, S. equorum and S. xylosus, were not found in clinical samples. The identification of CNS species and the characterisation of the genetic diversity of the strains constitute a first step towards CNS safety assessment