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Biocatalysis and Agricultural Biotechnology
Volume 18, 2019, 101013

Incorporation of microencapsulated Lactobacillus rhamnosus into infant-foods inhibit proliferation of toxicogenic Bacillus cereus strains

Pedro Rodríguez-Lópeza, Marta Bernárdeza, Juan J.Rodríguez-Herreraa, Ángel S.Comesañab, Marta L.Caboa

Department of Microbiology and Technology of Marine Products, Instituto de Investigaciones Marinas (IIM-CSIC), Eduardo Cabello 6, 36208 Vigo (Pontevedra), Spain.

Abstract

The main aim of this study was to localise, identify and characterise the Listeria monocytogenes-harbouring bacterial communities present in food related premises via 16S rRNA gene metagenetic analysis. With this scope, 319 environmental samples coming from a wide variety of surfaces of fish (n = 120), meat (n = 80) and dairy industries (n = 119), were firstly analysed following ISO 11290–1 and ISO 11290–2 norms. Direct L. monocytogenes quantification was possible in 9 samples (2.8%) with values between 2.00 and 3.97 log CFU/cm2. After enrichment, an overall L. monocytogenes incidence of 12.54% (n = 40) was obtained, being samples from meat industry the most contaminated. Molecular serotyping assays showed that most of the isolates belonged to 1/2b-3b-7 subgroup, followed by 1/2a-3a and 1/2c-3c. These results combined with AscI and ApaI PFGE macrorestriction patterns, yielded 7 different L. monocytogenes clusters. Nevertheless, no clear ecological relationships could be stablished. High amounts of L. monocytogenes-associated psychrotrophic microbiota were obtained in all cases with values above 9 log CFU/cm2 in some cases. Metagenetic analysis of one representative sample per each food industry type (fish, meat, dairy) demonstrated that Actinobacteria (53.16%) was mostly present in the meat sample whereas Proteobacteria was the most representative phylum in dairy (69.58%) and fish (97.11%) samples. Subsequent operational taxonomic units (OTUs) analysis, showed a wide variety of taxa associated with L. monocytogenes such as spoilage-associated genera (e.g. Psyschromonas or Shewanella), lactic acid bacteria genera (e.g. Lactococcus or Lactobacillus) or pathogenic species such as Yersinia enterocolitica. It was thus demonstrated, that L. monocytogenes is capable to both survive with different bacteria in different ecological niches, highlighting once more the need for proper surveillance schedules so as to guarantee the safety of the food products.

Keywords: Bacterial communities, Food industry, Food safety, High throughput sequencing, Listeria monocytogenes, Survey.

 
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